System.Data.SQLite

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Overview
Comment:Update SQLite core library to the latest trunk code.
Downloads: Tarball | ZIP archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: d4447158f660df8d74ed5ee0308eca8c1b29c54f
User & Date: mistachkin 2015-07-24 00:17:45.167
Context
2015-07-24
00:59
Enhance the test suite infrastructure to permit a non-default .NET Framework version to be used for a particular 'build year'. check-in: 13498a4979 user: mistachkin tags: trunk
00:32
Preliminary updates to the download page. check-in: 7dbf8439b5 user: mistachkin tags: preRelease
00:17
Update SQLite core library to the latest trunk code. check-in: d4447158f6 user: mistachkin tags: trunk
2015-07-23
04:40
In the batch build tool, attempt to make sure the target solution/project file matches up with the .NET Framework used. check-in: 49d0228259 user: mistachkin tags: trunk
Changes
Unified Diff Ignore Whitespace Patch
Changes to SQLite.Interop/src/core/sqlite3.c.
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**
** See also: [sqlite3_libversion()],
** [sqlite3_libversion_number()], [sqlite3_sourceid()],
** [sqlite_version()] and [sqlite_source_id()].
*/
#define SQLITE_VERSION        "3.8.11"
#define SQLITE_VERSION_NUMBER 3008011
#define SQLITE_SOURCE_ID      "2015-07-21 19:22:35 01c8b9ccfa0f336dfead7c004de3de571753f707"

/*
** CAPI3REF: Run-Time Library Version Numbers
** KEYWORDS: sqlite3_version, sqlite3_sourceid
**
** These interfaces provide the same information as the [SQLITE_VERSION],
** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros







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**
** See also: [sqlite3_libversion()],
** [sqlite3_libversion_number()], [sqlite3_sourceid()],
** [sqlite_version()] and [sqlite_source_id()].
*/
#define SQLITE_VERSION        "3.8.11"
#define SQLITE_VERSION_NUMBER 3008011
#define SQLITE_SOURCE_ID      "2015-07-24 00:02:15 119883a21bdcab66c15d1e80f3da20addda328ad"

/*
** CAPI3REF: Run-Time Library Version Numbers
** KEYWORDS: sqlite3_version, sqlite3_sourceid
**
** These interfaces provide the same information as the [SQLITE_VERSION],
** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros
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** circumstances in order to fix a problem with priority inversion.
** Applications should <em>not</em> use this file-control.
**
** <li>[[SQLITE_FCNTL_ZIPVFS]]
** The [SQLITE_FCNTL_ZIPVFS] opcode is implemented by zipvfs only. All other
** VFS should return SQLITE_NOTFOUND for this opcode.
**
** <li>[[SQLITE_FCNTL_OTA]]
** The [SQLITE_FCNTL_OTA] opcode is implemented by the special VFS used by
** the OTA extension only.  All other VFS should return SQLITE_NOTFOUND for
** this opcode.  
** </ul>
*/
#define SQLITE_FCNTL_LOCKSTATE               1
#define SQLITE_FCNTL_GET_LOCKPROXYFILE       2
#define SQLITE_FCNTL_SET_LOCKPROXYFILE       3
#define SQLITE_FCNTL_LAST_ERRNO              4







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** circumstances in order to fix a problem with priority inversion.
** Applications should <em>not</em> use this file-control.
**
** <li>[[SQLITE_FCNTL_ZIPVFS]]
** The [SQLITE_FCNTL_ZIPVFS] opcode is implemented by zipvfs only. All other
** VFS should return SQLITE_NOTFOUND for this opcode.
**
** <li>[[SQLITE_FCNTL_RBU]]
** The [SQLITE_FCNTL_RBU] opcode is implemented by the special VFS used by
** the RBU extension only.  All other VFS should return SQLITE_NOTFOUND for
** this opcode.  
** </ul>
*/
#define SQLITE_FCNTL_LOCKSTATE               1
#define SQLITE_FCNTL_GET_LOCKPROXYFILE       2
#define SQLITE_FCNTL_SET_LOCKPROXYFILE       3
#define SQLITE_FCNTL_LAST_ERRNO              4
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#define SQLITE_FCNTL_TRACE                  19
#define SQLITE_FCNTL_HAS_MOVED              20
#define SQLITE_FCNTL_SYNC                   21
#define SQLITE_FCNTL_COMMIT_PHASETWO        22
#define SQLITE_FCNTL_WIN32_SET_HANDLE       23
#define SQLITE_FCNTL_WAL_BLOCK              24
#define SQLITE_FCNTL_ZIPVFS                 25
#define SQLITE_FCNTL_OTA                    26

/* deprecated names */
#define SQLITE_GET_LOCKPROXYFILE      SQLITE_FCNTL_GET_LOCKPROXYFILE
#define SQLITE_SET_LOCKPROXYFILE      SQLITE_FCNTL_SET_LOCKPROXYFILE
#define SQLITE_LAST_ERRNO             SQLITE_FCNTL_LAST_ERRNO









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#define SQLITE_FCNTL_TRACE                  19
#define SQLITE_FCNTL_HAS_MOVED              20
#define SQLITE_FCNTL_SYNC                   21
#define SQLITE_FCNTL_COMMIT_PHASETWO        22
#define SQLITE_FCNTL_WIN32_SET_HANDLE       23
#define SQLITE_FCNTL_WAL_BLOCK              24
#define SQLITE_FCNTL_ZIPVFS                 25
#define SQLITE_FCNTL_RBU                    26

/* deprecated names */
#define SQLITE_GET_LOCKPROXYFILE      SQLITE_FCNTL_GET_LOCKPROXYFILE
#define SQLITE_SET_LOCKPROXYFILE      SQLITE_FCNTL_SET_LOCKPROXYFILE
#define SQLITE_LAST_ERRNO             SQLITE_FCNTL_LAST_ERRNO


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              int nPk = pPk->nKeyCol;
              int iPk;

              /* Read the PK into an array of temp registers. */
              r = sqlite3GetTempRange(pParse, nPk);
              for(iPk=0; iPk<nPk; iPk++){
                int iCol = pPk->aiColumn[iPk];

                sqlite3ExprCodeGetColumn(pParse, pTab, iCol, iCur, r+iPk, 0);



              }

              /* Check if the temp table already contains this key. If so,
              ** the row has already been included in the result set and
              ** can be ignored (by jumping past the Gosub below). Otherwise,
              ** insert the key into the temp table and proceed with processing
              ** the row.







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              int nPk = pPk->nKeyCol;
              int iPk;

              /* Read the PK into an array of temp registers. */
              r = sqlite3GetTempRange(pParse, nPk);
              for(iPk=0; iPk<nPk; iPk++){
                int iCol = pPk->aiColumn[iPk];
                int rx;
                rx = sqlite3ExprCodeGetColumn(pParse, pTab, iCol, iCur,r+iPk,0);
                if( rx!=r+iPk ){
                  sqlite3VdbeAddOp2(v, OP_SCopy, rx, r+iPk);
                }
              }

              /* Check if the temp table already contains this key. If so,
              ** the row has already been included in the result set and
              ** can be ignored (by jumping past the Gosub below). Otherwise,
              ** insert the key into the temp table and proceed with processing
              ** the row.
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** The sz parameter is the number of bytes in each lookaside slot.
** The cnt parameter is the number of slots.  If pStart is NULL the
** space for the lookaside memory is obtained from sqlite3_malloc().
** If pStart is not NULL then it is sz*cnt bytes of memory to use for
** the lookaside memory.
*/
static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){

  void *pStart;
  if( db->lookaside.nOut ){
    return SQLITE_BUSY;
  }
  /* Free any existing lookaside buffer for this handle before
  ** allocating a new one so we don't have to have space for 
  ** both at the same time.







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** The sz parameter is the number of bytes in each lookaside slot.
** The cnt parameter is the number of slots.  If pStart is NULL the
** space for the lookaside memory is obtained from sqlite3_malloc().
** If pStart is not NULL then it is sz*cnt bytes of memory to use for
** the lookaside memory.
*/
static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
#ifndef SQLITE_OMIT_LOOKASIDE
  void *pStart;
  if( db->lookaside.nOut ){
    return SQLITE_BUSY;
  }
  /* Free any existing lookaside buffer for this handle before
  ** allocating a new one so we don't have to have space for 
  ** both at the same time.
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    db->lookaside.bMalloced = pBuf==0 ?1:0;
  }else{
    db->lookaside.pStart = db;
    db->lookaside.pEnd = db;
    db->lookaside.bEnabled = 0;
    db->lookaside.bMalloced = 0;
  }

  return SQLITE_OK;
}

/*
** Return the mutex associated with a database connection.
*/
SQLITE_API sqlite3_mutex *SQLITE_STDCALL sqlite3_db_mutex(sqlite3 *db){







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    db->lookaside.bMalloced = pBuf==0 ?1:0;
  }else{
    db->lookaside.pStart = db;
    db->lookaside.pEnd = db;
    db->lookaside.bEnabled = 0;
    db->lookaside.bMalloced = 0;
  }
#endif /* SQLITE_OMIT_LOOKASIDE */
  return SQLITE_OK;
}

/*
** Return the mutex associated with a database connection.
*/
SQLITE_API sqlite3_mutex *SQLITE_STDCALL sqlite3_db_mutex(sqlite3 *db){
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  *ppModule = &icuTokenizerModule;
}

#endif /* defined(SQLITE_ENABLE_ICU) */
#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */

/************** End of fts3_icu.c ********************************************/
/************** Begin file sqlite3ota.c **************************************/
/*
** 2014 August 30
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
**
** OVERVIEW 
**
**  The OTA extension requires that the OTA update be packaged as an
**  SQLite database. The tables it expects to find are described in
**  sqlite3ota.h.  Essentially, for each table xyz in the target database
**  that the user wishes to write to, a corresponding data_xyz table is
**  created in the OTA database and populated with one row for each row to
**  update, insert or delete from the target table.
** 
**  The update proceeds in three stages:
** 
**  1) The database is updated. The modified database pages are written
**     to a *-oal file. A *-oal file is just like a *-wal file, except
**     that it is named "<database>-oal" instead of "<database>-wal".
**     Because regular SQLite clients do not look for file named
**     "<database>-oal", they go on using the original database in
**     rollback mode while the *-oal file is being generated.
** 
**     During this stage OTA does not update the database by writing
**     directly to the target tables. Instead it creates "imposter"
**     tables using the SQLITE_TESTCTRL_IMPOSTER interface that it uses
**     to update each b-tree individually. All updates required by each
**     b-tree are completed before moving on to the next, and all
**     updates are done in sorted key order.
** 
**  2) The "<database>-oal" file is moved to the equivalent "<database>-wal"
**     location using a call to rename(2). Before doing this the OTA
**     module takes an EXCLUSIVE lock on the database file, ensuring
**     that there are no other active readers.
** 
**     Once the EXCLUSIVE lock is released, any other database readers
**     detect the new *-wal file and read the database in wal mode. At
**     this point they see the new version of the database - including
**     the updates made as part of the OTA update.
** 
**  3) The new *-wal file is checkpointed. This proceeds in the same way 
**     as a regular database checkpoint, except that a single frame is
**     checkpointed each time sqlite3ota_step() is called. If the OTA
**     handle is closed before the entire *-wal file is checkpointed,
**     the checkpoint progress is saved in the OTA database and the
**     checkpoint can be resumed by another OTA client at some point in
**     the future.
**
** POTENTIAL PROBLEMS
** 
**  The rename() call might not be portable. And OTA is not currently
**  syncing the directory after renaming the file.
**
**  When state is saved, any commit to the *-oal file and the commit to
**  the OTA update database are not atomic. So if the power fails at the
**  wrong moment they might get out of sync. As the main database will be
**  committed before the OTA update database this will likely either just
**  pass unnoticed, or result in SQLITE_CONSTRAINT errors (due to UNIQUE
**  constraint violations).
**
**  If some client does modify the target database mid OTA update, or some
**  other error occurs, the OTA extension will keep throwing errors. It's
**  not really clear how to get out of this state. The system could just
**  by delete the OTA update database and *-oal file and have the device
**  download the update again and start over.
**
**  At present, for an UPDATE, both the new.* and old.* records are
**  collected in the ota_xyz table. And for both UPDATEs and DELETEs all
**  fields are collected.  This means we're probably writing a lot more
**  data to disk when saving the state of an ongoing update to the OTA
**  update database than is strictly necessary.
** 
*/

/* #include <assert.h> */
/* #include <string.h> */
/* #include <stdio.h> */
/* #include <unistd.h> */

/* #include "sqlite3.h" */

#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_OTA)
/************** Include sqlite3ota.h in the middle of sqlite3ota.c ***********/
/************** Begin file sqlite3ota.h **************************************/
/*
** 2014 August 30
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains the public interface for the OTA extension. 
*/

/*
** SUMMARY
**
** Writing a transaction containing a large number of operations on 
** b-tree indexes that are collectively larger than the available cache







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  *ppModule = &icuTokenizerModule;
}

#endif /* defined(SQLITE_ENABLE_ICU) */
#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */

/************** End of fts3_icu.c ********************************************/
/************** Begin file sqlite3rbu.c **************************************/
/*
** 2014 August 30
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
**
** OVERVIEW 
**
**  The RBU extension requires that the RBU update be packaged as an
**  SQLite database. The tables it expects to find are described in
**  sqlite3rbu.h.  Essentially, for each table xyz in the target database
**  that the user wishes to write to, a corresponding data_xyz table is
**  created in the RBU database and populated with one row for each row to
**  update, insert or delete from the target table.
** 
**  The update proceeds in three stages:
** 
**  1) The database is updated. The modified database pages are written
**     to a *-oal file. A *-oal file is just like a *-wal file, except
**     that it is named "<database>-oal" instead of "<database>-wal".
**     Because regular SQLite clients do not look for file named
**     "<database>-oal", they go on using the original database in
**     rollback mode while the *-oal file is being generated.
** 
**     During this stage RBU does not update the database by writing
**     directly to the target tables. Instead it creates "imposter"
**     tables using the SQLITE_TESTCTRL_IMPOSTER interface that it uses
**     to update each b-tree individually. All updates required by each
**     b-tree are completed before moving on to the next, and all
**     updates are done in sorted key order.
** 
**  2) The "<database>-oal" file is moved to the equivalent "<database>-wal"
**     location using a call to rename(2). Before doing this the RBU
**     module takes an EXCLUSIVE lock on the database file, ensuring
**     that there are no other active readers.
** 
**     Once the EXCLUSIVE lock is released, any other database readers
**     detect the new *-wal file and read the database in wal mode. At
**     this point they see the new version of the database - including
**     the updates made as part of the RBU update.
** 
**  3) The new *-wal file is checkpointed. This proceeds in the same way 
**     as a regular database checkpoint, except that a single frame is
**     checkpointed each time sqlite3rbu_step() is called. If the RBU
**     handle is closed before the entire *-wal file is checkpointed,
**     the checkpoint progress is saved in the RBU database and the
**     checkpoint can be resumed by another RBU client at some point in
**     the future.
**
** POTENTIAL PROBLEMS
** 
**  The rename() call might not be portable. And RBU is not currently
**  syncing the directory after renaming the file.
**
**  When state is saved, any commit to the *-oal file and the commit to
**  the RBU update database are not atomic. So if the power fails at the
**  wrong moment they might get out of sync. As the main database will be
**  committed before the RBU update database this will likely either just
**  pass unnoticed, or result in SQLITE_CONSTRAINT errors (due to UNIQUE
**  constraint violations).
**
**  If some client does modify the target database mid RBU update, or some
**  other error occurs, the RBU extension will keep throwing errors. It's
**  not really clear how to get out of this state. The system could just
**  by delete the RBU update database and *-oal file and have the device
**  download the update again and start over.
**
**  At present, for an UPDATE, both the new.* and old.* records are
**  collected in the rbu_xyz table. And for both UPDATEs and DELETEs all
**  fields are collected.  This means we're probably writing a lot more
**  data to disk when saving the state of an ongoing update to the RBU
**  update database than is strictly necessary.
** 
*/

/* #include <assert.h> */
/* #include <string.h> */
/* #include <stdio.h> */
/* #include <unistd.h> */

/* #include "sqlite3.h" */

#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_RBU)
/************** Include sqlite3rbu.h in the middle of sqlite3rbu.c ***********/
/************** Begin file sqlite3rbu.h **************************************/
/*
** 2014 August 30
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains the public interface for the RBU extension. 
*/

/*
** SUMMARY
**
** Writing a transaction containing a large number of operations on 
** b-tree indexes that are collectively larger than the available cache
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** guarantee that a single update process will run for long enough to apply 
** the entire update, for example because the update is being applied on a 
** mobile device that is frequently rebooted. Even after the writer process 
** has committed one or more sub-transactions, other database clients continue
** to read from the original database snapshot. In other words, partially 
** applied transactions are not visible to other clients. 
**
** "OTA" stands for "Over The Air" update. As in a large database update
** transmitted via a wireless network to a mobile device. A transaction
** applied using this extension is hence refered to as an "OTA update".
**
**
** LIMITATIONS
**
** An "OTA update" transaction is subject to the following limitations:
**
**   * The transaction must consist of INSERT, UPDATE and DELETE operations
**     only.
**
**   * INSERT statements may not use any default values.
**
**   * UPDATE and DELETE statements must identify their target rows by 







|

|




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** guarantee that a single update process will run for long enough to apply 
** the entire update, for example because the update is being applied on a 
** mobile device that is frequently rebooted. Even after the writer process 
** has committed one or more sub-transactions, other database clients continue
** to read from the original database snapshot. In other words, partially 
** applied transactions are not visible to other clients. 
**
** "RBU" stands for "Resumable Bulk Update". As in a large database update
** transmitted via a wireless network to a mobile device. A transaction
** applied using this extension is hence refered to as an "RBU update".
**
**
** LIMITATIONS
**
** An "RBU update" transaction is subject to the following limitations:
**
**   * The transaction must consist of INSERT, UPDATE and DELETE operations
**     only.
**
**   * INSERT statements may not use any default values.
**
**   * UPDATE and DELETE statements must identify their target rows by 
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**   * CHECK constraints are not enforced.
**
**   * No constraint handling mode except for "OR ROLLBACK" is supported.
**
**
** PREPARATION
**
** An "OTA update" is stored as a separate SQLite database. A database
** containing an OTA update is an "OTA database". For each table in the 
** target database to be updated, the OTA database should contain a table
** named "data_<target name>" containing the same set of columns as the
** target table, and one more - "ota_control". The data_% table should 
** have no PRIMARY KEY or UNIQUE constraints, but each column should have
** the same type as the corresponding column in the target database.
** The "ota_control" column should have no type at all. For example, if
** the target database contains:
**
**   CREATE TABLE t1(a INTEGER PRIMARY KEY, b TEXT, c UNIQUE);
**
** Then the OTA database should contain:
**
**   CREATE TABLE data_t1(a INTEGER, b TEXT, c, ota_control);
**
** The order of the columns in the data_% table does not matter.
**
** If the target database table is a virtual table or a table that has no
** PRIMARY KEY declaration, the data_% table must also contain a column 
** named "ota_rowid". This column is mapped to the tables implicit primary 
** key column - "rowid". Virtual tables for which the "rowid" column does 
** not function like a primary key value cannot be updated using OTA. For 
** example, if the target db contains either of the following:
**
**   CREATE VIRTUAL TABLE x1 USING fts3(a, b);
**   CREATE TABLE x1(a, b)
**
** then the OTA database should contain:
**
**   CREATE TABLE data_x1(a, b, ota_rowid, ota_control);
**
** All non-hidden columns (i.e. all columns matched by "SELECT *") of the
** target table must be present in the input table. For virtual tables,
** hidden columns are optional - they are updated by OTA if present in
** the input table, or not otherwise. For example, to write to an fts4
** table with a hidden languageid column such as:
**
**   CREATE VIRTUAL TABLE ft1 USING fts4(a, b, languageid='langid');
**
** Either of the following input table schemas may be used:
**
**   CREATE TABLE data_ft1(a, b, langid, ota_rowid, ota_control);
**   CREATE TABLE data_ft1(a, b, ota_rowid, ota_control);
**
** For each row to INSERT into the target database as part of the OTA 
** update, the corresponding data_% table should contain a single record
** with the "ota_control" column set to contain integer value 0. The
** other columns should be set to the values that make up the new record 
** to insert. 
**
** If the target database table has an INTEGER PRIMARY KEY, it is not 
** possible to insert a NULL value into the IPK column. Attempting to 
** do so results in an SQLITE_MISMATCH error.
**
** For each row to DELETE from the target database as part of the OTA 
** update, the corresponding data_% table should contain a single record
** with the "ota_control" column set to contain integer value 1. The
** real primary key values of the row to delete should be stored in the
** corresponding columns of the data_% table. The values stored in the
** other columns are not used.
**
** For each row to UPDATE from the target database as part of the OTA 
** update, the corresponding data_% table should contain a single record
** with the "ota_control" column set to contain a value of type text.
** The real primary key values identifying the row to update should be 
** stored in the corresponding columns of the data_% table row, as should
** the new values of all columns being update. The text value in the 
** "ota_control" column must contain the same number of characters as
** there are columns in the target database table, and must consist entirely
** of 'x' and '.' characters (or in some special cases 'd' - see below). For 
** each column that is being updated, the corresponding character is set to
** 'x'. For those that remain as they are, the corresponding character of the
** ota_control value should be set to '.'. For example, given the tables 
** above, the update statement:
**
**   UPDATE t1 SET c = 'usa' WHERE a = 4;
**
** is represented by the data_t1 row created by:
**
**   INSERT INTO data_t1(a, b, c, ota_control) VALUES(4, NULL, 'usa', '..x');
**
** Instead of an 'x' character, characters of the ota_control value specified
** for UPDATEs may also be set to 'd'. In this case, instead of updating the
** target table with the value stored in the corresponding data_% column, the
** user-defined SQL function "ota_delta()" is invoked and the result stored in
** the target table column. ota_delta() is invoked with two arguments - the
** original value currently stored in the target table column and the 
** value specified in the data_xxx table.
**
** For example, this row:
**
**   INSERT INTO data_t1(a, b, c, ota_control) VALUES(4, NULL, 'usa', '..d');
**
** is similar to an UPDATE statement such as: 
**
**   UPDATE t1 SET c = ota_delta(c, 'usa') WHERE a = 4;
**
** If the target database table is a virtual table or a table with no PRIMARY
** KEY, the ota_control value should not include a character corresponding 
** to the ota_rowid value. For example, this:
**
**   INSERT INTO data_ft1(a, b, ota_rowid, ota_control) 
**       VALUES(NULL, 'usa', 12, '.x');
**
** causes a result similar to:
**
**   UPDATE ft1 SET b = 'usa' WHERE rowid = 12;
**
** The data_xxx tables themselves should have no PRIMARY KEY declarations.
** However, OTA is more efficient if reading the rows in from each data_xxx
** table in "rowid" order is roughly the same as reading them sorted by
** the PRIMARY KEY of the corresponding target database table. In other 
** words, rows should be sorted using the destination table PRIMARY KEY 
** fields before they are inserted into the data_xxx tables.
**
** USAGE
**
** The API declared below allows an application to apply an OTA update 
** stored on disk to an existing target database. Essentially, the 
** application:
**
**     1) Opens an OTA handle using the sqlite3ota_open() function.
**
**     2) Registers any required virtual table modules with the database
**        handle returned by sqlite3ota_db(). Also, if required, register
**        the ota_delta() implementation.
**
**     3) Calls the sqlite3ota_step() function one or more times on
**        the new handle. Each call to sqlite3ota_step() performs a single
**        b-tree operation, so thousands of calls may be required to apply 
**        a complete update.
**
**     4) Calls sqlite3ota_close() to close the OTA update handle. If
**        sqlite3ota_step() has been called enough times to completely
**        apply the update to the target database, then the OTA database
**        is marked as fully applied. Otherwise, the state of the OTA 
**        update application is saved in the OTA database for later 
**        resumption.
**
** See comments below for more detail on APIs.
**
** If an update is only partially applied to the target database by the
** time sqlite3ota_close() is called, various state information is saved 
** within the OTA database. This allows subsequent processes to automatically
** resume the OTA update from where it left off.
**
** To remove all OTA extension state information, returning an OTA database 
** to its original contents, it is sufficient to drop all tables that begin
** with the prefix "ota_"
**
** DATABASE LOCKING
**
** An OTA update may not be applied to a database in WAL mode. Attempting
** to do so is an error (SQLITE_ERROR).
**
** While an OTA handle is open, a SHARED lock may be held on the target
** database file. This means it is possible for other clients to read the
** database, but not to write it.
**
** If an OTA update is started and then suspended before it is completed,
** then an external client writes to the database, then attempting to resume
** the suspended OTA update is also an error (SQLITE_BUSY).
*/

#ifndef _SQLITE3OTA_H
#define _SQLITE3OTA_H

/* #include "sqlite3.h"              ** Required for error code definitions ** */

typedef struct sqlite3ota sqlite3ota;

/*
** Open an OTA handle.
**
** Argument zTarget is the path to the target database. Argument zOta is
** the path to the OTA database. Each call to this function must be matched
** by a call to sqlite3ota_close(). When opening the databases, OTA passes
** the SQLITE_CONFIG_URI flag to sqlite3_open_v2(). So if either zTarget
** or zOta begin with "file:", it will be interpreted as an SQLite 
** database URI, not a regular file name.
**
** If the zState argument is passed a NULL value, the OTA extension stores 
** the current state of the update (how many rows have been updated, which 
** indexes are yet to be updated etc.) within the OTA database itself. This
** can be convenient, as it means that the OTA application does not need to
** organize removing a separate state file after the update is concluded. 
** Or, if zState is non-NULL, it must be a path to a database file in which 
** the OTA extension can store the state of the update.
**
** When resuming an OTA update, the zState argument must be passed the same
** value as when the OTA update was started.
**
** Once the OTA update is finished, the OTA extension does not 
** automatically remove any zState database file, even if it created it.
**
** By default, OTA uses the default VFS to access the files on disk. To
** use a VFS other than the default, an SQLite "file:" URI containing a
** "vfs=..." option may be passed as the zTarget option.
**
** IMPORTANT NOTE FOR ZIPVFS USERS: The OTA extension works with all of
** SQLite's built-in VFSs, including the multiplexor VFS. However it does
** not work out of the box with zipvfs. Refer to the comment describing
** the zipvfs_create_vfs() API below for details on using OTA with zipvfs.
*/
SQLITE_API sqlite3ota *SQLITE_STDCALL sqlite3ota_open(
  const char *zTarget, 
  const char *zOta,
  const char *zState
);

/*
** Internally, each OTA connection uses a separate SQLite database 
** connection to access the target and ota update databases. This
** API allows the application direct access to these database handles.
**
** The first argument passed to this function must be a valid, open, OTA
** handle. The second argument should be passed zero to access the target
** database handle, or non-zero to access the ota update database handle.
** Accessing the underlying database handles may be useful in the
** following scenarios:
**
**   * If any target tables are virtual tables, it may be necessary to
**     call sqlite3_create_module() on the target database handle to 
**     register the required virtual table implementations.
**
**   * If the data_xxx tables in the OTA source database are virtual 
**     tables, the application may need to call sqlite3_create_module() on
**     the ota update db handle to any required virtual table
**     implementations.
**
**   * If the application uses the "ota_delta()" feature described above,
**     it must use sqlite3_create_function() or similar to register the
**     ota_delta() implementation with the target database handle.
**
** If an error has occurred, either while opening or stepping the OTA object,
** this function may return NULL. The error code and message may be collected
** when sqlite3ota_close() is called.
*/
SQLITE_API sqlite3 *SQLITE_STDCALL sqlite3ota_db(sqlite3ota*, int bOta);

/*
** Do some work towards applying the OTA update to the target db. 
**
** Return SQLITE_DONE if the update has been completely applied, or 
** SQLITE_OK if no error occurs but there remains work to do to apply
** the OTA update. If an error does occur, some other error code is 
** returned. 
**
** Once a call to sqlite3ota_step() has returned a value other than
** SQLITE_OK, all subsequent calls on the same OTA handle are no-ops
** that immediately return the same value.
*/
SQLITE_API int SQLITE_STDCALL sqlite3ota_step(sqlite3ota *pOta);

/*
** Close an OTA handle. 
**
** If the OTA update has been completely applied, mark the OTA database
** as fully applied. Otherwise, assuming no error has occurred, save the
** current state of the OTA update appliation to the OTA database.
**
** If an error has already occurred as part of an sqlite3ota_step()
** or sqlite3ota_open() call, or if one occurs within this function, an
** SQLite error code is returned. Additionally, *pzErrmsg may be set to
** point to a buffer containing a utf-8 formatted English language error
** message. It is the responsibility of the caller to eventually free any 
** such buffer using sqlite3_free().
**
** Otherwise, if no error occurs, this function returns SQLITE_OK if the
** update has been partially applied, or SQLITE_DONE if it has been 
** completely applied.
*/
SQLITE_API int SQLITE_STDCALL sqlite3ota_close(sqlite3ota *pOta, char **pzErrmsg);

/*
** Return the total number of key-value operations (inserts, deletes or 
** updates) that have been performed on the target database since the
** current OTA update was started.
*/
SQLITE_API sqlite3_int64 SQLITE_STDCALL sqlite3ota_progress(sqlite3ota *pOta);

/*
** Create an OTA VFS named zName that accesses the underlying file-system
** via existing VFS zParent. Or, if the zParent parameter is passed NULL, 
** then the new OTA VFS uses the default system VFS to access the file-system.
** The new object is registered as a non-default VFS with SQLite before 
** returning.
**
** Part of the OTA implementation uses a custom VFS object. Usually, this
** object is created and deleted automatically by OTA. 
**
** The exception is for applications that also use zipvfs. In this case,
** the custom VFS must be explicitly created by the user before the OTA
** handle is opened. The OTA VFS should be installed so that the zipvfs
** VFS uses the OTA VFS, which in turn uses any other VFS layers in use 
** (for example multiplexor) to access the file-system. For example,
** to assemble an OTA enabled VFS stack that uses both zipvfs and 
** multiplexor (error checking omitted):
**
**     // Create a VFS named "multiplex" (not the default).
**     sqlite3_multiplex_initialize(0, 0);
**
**     // Create an ota VFS named "ota" that uses multiplexor. If the
**     // second argument were replaced with NULL, the "ota" VFS would
**     // access the file-system via the system default VFS, bypassing the
**     // multiplexor.
**     sqlite3ota_create_vfs("ota", "multiplex");
**
**     // Create a zipvfs VFS named "zipvfs" that uses ota.
**     zipvfs_create_vfs_v3("zipvfs", "ota", 0, xCompressorAlgorithmDetector);
**
**     // Make zipvfs the default VFS.
**     sqlite3_vfs_register(sqlite3_vfs_find("zipvfs"), 1);
**
** Because the default VFS created above includes a OTA functionality, it
** may be used by OTA clients. Attempting to use OTA with a zipvfs VFS stack
** that does not include the OTA layer results in an error.
**
** The overhead of adding the "ota" VFS to the system is negligible for 
** non-OTA users. There is no harm in an application accessing the 
** file-system via "ota" all the time, even if it only uses OTA functionality 
** occasionally.
*/
SQLITE_API int SQLITE_STDCALL sqlite3ota_create_vfs(const char *zName, const char *zParent);

/*
** Deregister and destroy an OTA vfs created by an earlier call to
** sqlite3ota_create_vfs().
**
** VFS objects are not reference counted. If a VFS object is destroyed
** before all database handles that use it have been closed, the results
** are undefined.
*/
SQLITE_API void SQLITE_STDCALL sqlite3ota_destroy_vfs(const char *zName);

#endif /* _SQLITE3OTA_H */

/************** End of sqlite3ota.h ******************************************/
/************** Continuing where we left off in sqlite3ota.c *****************/

/* Maximum number of prepared UPDATE statements held by this module */
#define SQLITE_OTA_UPDATE_CACHESIZE 16

/*
** Swap two objects of type TYPE.
*/
#if !defined(SQLITE_AMALGAMATION)
# define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
#endif

/*
** The ota_state table is used to save the state of a partially applied
** update so that it can be resumed later. The table consists of integer
** keys mapped to values as follows:
**
** OTA_STATE_STAGE:
**   May be set to integer values 1, 2, 4 or 5. As follows:
**       1: the *-ota file is currently under construction.
**       2: the *-ota file has been constructed, but not yet moved 
**          to the *-wal path.
**       4: the checkpoint is underway.
**       5: the ota update has been checkpointed.
**
** OTA_STATE_TBL:
**   Only valid if STAGE==1. The target database name of the table 
**   currently being written.
**
** OTA_STATE_IDX:
**   Only valid if STAGE==1. The target database name of the index 
**   currently being written, or NULL if the main table is currently being
**   updated.
**
** OTA_STATE_ROW:
**   Only valid if STAGE==1. Number of rows already processed for the current
**   table/index.
**
** OTA_STATE_PROGRESS:
**   Total number of sqlite3ota_step() calls made so far as part of this
**   ota update.
**
** OTA_STATE_CKPT:
**   Valid if STAGE==4. The 64-bit checksum associated with the wal-index
**   header created by recovering the *-wal file. This is used to detect
**   cases when another client appends frames to the *-wal file in the
**   middle of an incremental checkpoint (an incremental checkpoint cannot
**   be continued if this happens).
**
** OTA_STATE_COOKIE:
**   Valid if STAGE==1. The current change-counter cookie value in the 
**   target db file.
**
** OTA_STATE_OALSZ:
**   Valid if STAGE==1. The size in bytes of the *-oal file.
*/
#define OTA_STATE_STAGE       1
#define OTA_STATE_TBL         2
#define OTA_STATE_IDX         3
#define OTA_STATE_ROW         4
#define OTA_STATE_PROGRESS    5
#define OTA_STATE_CKPT        6
#define OTA_STATE_COOKIE      7
#define OTA_STATE_OALSZ       8

#define OTA_STAGE_OAL         1
#define OTA_STAGE_MOVE        2
#define OTA_STAGE_CAPTURE     3
#define OTA_STAGE_CKPT        4
#define OTA_STAGE_DONE        5


#define OTA_CREATE_STATE \
  "CREATE TABLE IF NOT EXISTS %s.ota_state(k INTEGER PRIMARY KEY, v)"

typedef struct OtaFrame OtaFrame;
typedef struct OtaObjIter OtaObjIter;
typedef struct OtaState OtaState;
typedef struct ota_vfs ota_vfs;
typedef struct ota_file ota_file;
typedef struct OtaUpdateStmt OtaUpdateStmt;

#if !defined(SQLITE_AMALGAMATION)
typedef unsigned int u32;
typedef unsigned char u8;
typedef sqlite3_int64 i64;
#endif

/*
** These values must match the values defined in wal.c for the equivalent
** locks. These are not magic numbers as they are part of the SQLite file
** format.
*/
#define WAL_LOCK_WRITE  0
#define WAL_LOCK_CKPT   1
#define WAL_LOCK_READ0  3

/*
** A structure to store values read from the ota_state table in memory.
*/
struct OtaState {
  int eStage;
  char *zTbl;
  char *zIdx;
  i64 iWalCksum;
  int nRow;
  i64 nProgress;
  u32 iCookie;
  i64 iOalSz;
};

struct OtaUpdateStmt {
  char *zMask;                    /* Copy of update mask used with pUpdate */
  sqlite3_stmt *pUpdate;          /* Last update statement (or NULL) */
  OtaUpdateStmt *pNext;
};

/*
** An iterator of this type is used to iterate through all objects in
** the target database that require updating. For each such table, the
** iterator visits, in order:
**
**     * the table itself, 
**     * each index of the table (zero or more points to visit), and
**     * a special "cleanup table" state.
**
** abIndexed:
**   If the table has no indexes on it, abIndexed is set to NULL. Otherwise,
**   it points to an array of flags nTblCol elements in size. The flag is
**   set for each column that is either a part of the PK or a part of an
**   index. Or clear otherwise.
**   
*/
struct OtaObjIter {
  sqlite3_stmt *pTblIter;         /* Iterate through tables */
  sqlite3_stmt *pIdxIter;         /* Index iterator */
  int nTblCol;                    /* Size of azTblCol[] array */
  char **azTblCol;                /* Array of unquoted target column names */
  char **azTblType;               /* Array of target column types */
  int *aiSrcOrder;                /* src table col -> target table col */
  u8 *abTblPk;                    /* Array of flags, set on target PK columns */
  u8 *abNotNull;                  /* Array of flags, set on NOT NULL columns */
  u8 *abIndexed;                  /* Array of flags, set on indexed & PK cols */
  int eType;                      /* Table type - an OTA_PK_XXX value */

  /* Output variables. zTbl==0 implies EOF. */
  int bCleanup;                   /* True in "cleanup" state */
  const char *zTbl;               /* Name of target db table */
  const char *zIdx;               /* Name of target db index (or null) */
  int iTnum;                      /* Root page of current object */
  int iPkTnum;                    /* If eType==EXTERNAL, root of PK index */
  int bUnique;                    /* Current index is unique */

  /* Statements created by otaObjIterPrepareAll() */
  int nCol;                       /* Number of columns in current object */
  sqlite3_stmt *pSelect;          /* Source data */
  sqlite3_stmt *pInsert;          /* Statement for INSERT operations */
  sqlite3_stmt *pDelete;          /* Statement for DELETE ops */
  sqlite3_stmt *pTmpInsert;       /* Insert into ota_tmp_$zTbl */

  /* Last UPDATE used (for PK b-tree updates only), or NULL. */
  OtaUpdateStmt *pOtaUpdate;
};

/*
** Values for OtaObjIter.eType
**
**     0: Table does not exist (error)
**     1: Table has an implicit rowid.
**     2: Table has an explicit IPK column.
**     3: Table has an external PK index.
**     4: Table is WITHOUT ROWID.
**     5: Table is a virtual table.
*/
#define OTA_PK_NOTABLE        0
#define OTA_PK_NONE           1
#define OTA_PK_IPK            2
#define OTA_PK_EXTERNAL       3
#define OTA_PK_WITHOUT_ROWID  4
#define OTA_PK_VTAB           5


/*
** Within the OTA_STAGE_OAL stage, each call to sqlite3ota_step() performs
** one of the following operations.
*/
#define OTA_INSERT     1          /* Insert on a main table b-tree */
#define OTA_DELETE     2          /* Delete a row from a main table b-tree */
#define OTA_IDX_DELETE 3          /* Delete a row from an aux. index b-tree */
#define OTA_IDX_INSERT 4          /* Insert on an aux. index b-tree */
#define OTA_UPDATE     5          /* Update a row in a main table b-tree */


/*
** A single step of an incremental checkpoint - frame iWalFrame of the wal
** file should be copied to page iDbPage of the database file.
*/
struct OtaFrame {
  u32 iDbPage;
  u32 iWalFrame;
};

/*
** OTA handle.
*/
struct sqlite3ota {
  int eStage;                     /* Value of OTA_STATE_STAGE field */
  sqlite3 *dbMain;                /* target database handle */
  sqlite3 *dbOta;                 /* ota database handle */
  char *zTarget;                  /* Path to target db */
  char *zOta;                     /* Path to ota db */
  char *zState;                   /* Path to state db (or NULL if zOta) */
  char zStateDb[5];               /* Db name for state ("stat" or "main") */
  int rc;                         /* Value returned by last ota_step() call */
  char *zErrmsg;                  /* Error message if rc!=SQLITE_OK */
  int nStep;                      /* Rows processed for current object */
  int nProgress;                  /* Rows processed for all objects */
  OtaObjIter objiter;             /* Iterator for skipping through tbl/idx */
  const char *zVfsName;           /* Name of automatically created ota vfs */
  ota_file *pTargetFd;            /* File handle open on target db */
  i64 iOalSz;

  /* The following state variables are used as part of the incremental
  ** checkpoint stage (eStage==OTA_STAGE_CKPT). See comments surrounding
  ** function otaSetupCheckpoint() for details.  */
  u32 iMaxFrame;                  /* Largest iWalFrame value in aFrame[] */
  u32 mLock;
  int nFrame;                     /* Entries in aFrame[] array */
  int nFrameAlloc;                /* Allocated size of aFrame[] array */
  OtaFrame *aFrame;
  int pgsz;
  u8 *aBuf;
  i64 iWalCksum;
};

/*
** An ota VFS is implemented using an instance of this structure.
*/
struct ota_vfs {
  sqlite3_vfs base;               /* ota VFS shim methods */
  sqlite3_vfs *pRealVfs;          /* Underlying VFS */
  sqlite3_mutex *mutex;           /* Mutex to protect pMain */
  ota_file *pMain;                /* Linked list of main db files */
};

/*
** Each file opened by an ota VFS is represented by an instance of
** the following structure.
*/
struct ota_file {
  sqlite3_file base;              /* sqlite3_file methods */
  sqlite3_file *pReal;            /* Underlying file handle */
  ota_vfs *pOtaVfs;               /* Pointer to the ota_vfs object */
  sqlite3ota *pOta;               /* Pointer to ota object (ota target only) */

  int openFlags;                  /* Flags this file was opened with */
  u32 iCookie;                    /* Cookie value for main db files */
  u8 iWriteVer;                   /* "write-version" value for main db files */

  int nShm;                       /* Number of entries in apShm[] array */
  char **apShm;                   /* Array of mmap'd *-shm regions */
  char *zDel;                     /* Delete this when closing file */

  const char *zWal;               /* Wal filename for this main db file */
  ota_file *pWalFd;               /* Wal file descriptor for this main db */
  ota_file *pMainNext;            /* Next MAIN_DB file */
};


/*
** Prepare the SQL statement in buffer zSql against database handle db.
** If successful, set *ppStmt to point to the new statement and return
** SQLITE_OK. 







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**   * CHECK constraints are not enforced.
**
**   * No constraint handling mode except for "OR ROLLBACK" is supported.
**
**
** PREPARATION
**
** An "RBU update" is stored as a separate SQLite database. A database
** containing an RBU update is an "RBU database". For each table in the 
** target database to be updated, the RBU database should contain a table
** named "data_<target name>" containing the same set of columns as the
** target table, and one more - "rbu_control". The data_% table should 
** have no PRIMARY KEY or UNIQUE constraints, but each column should have
** the same type as the corresponding column in the target database.
** The "rbu_control" column should have no type at all. For example, if
** the target database contains:
**
**   CREATE TABLE t1(a INTEGER PRIMARY KEY, b TEXT, c UNIQUE);
**
** Then the RBU database should contain:
**
**   CREATE TABLE data_t1(a INTEGER, b TEXT, c, rbu_control);
**
** The order of the columns in the data_% table does not matter.
**
** If the target database table is a virtual table or a table that has no
** PRIMARY KEY declaration, the data_% table must also contain a column 
** named "rbu_rowid". This column is mapped to the tables implicit primary 
** key column - "rowid". Virtual tables for which the "rowid" column does 
** not function like a primary key value cannot be updated using RBU. For 
** example, if the target db contains either of the following:
**
**   CREATE VIRTUAL TABLE x1 USING fts3(a, b);
**   CREATE TABLE x1(a, b)
**
** then the RBU database should contain:
**
**   CREATE TABLE data_x1(a, b, rbu_rowid, rbu_control);
**
** All non-hidden columns (i.e. all columns matched by "SELECT *") of the
** target table must be present in the input table. For virtual tables,
** hidden columns are optional - they are updated by RBU if present in
** the input table, or not otherwise. For example, to write to an fts4
** table with a hidden languageid column such as:
**
**   CREATE VIRTUAL TABLE ft1 USING fts4(a, b, languageid='langid');
**
** Either of the following input table schemas may be used:
**
**   CREATE TABLE data_ft1(a, b, langid, rbu_rowid, rbu_control);
**   CREATE TABLE data_ft1(a, b, rbu_rowid, rbu_control);
**
** For each row to INSERT into the target database as part of the RBU 
** update, the corresponding data_% table should contain a single record
** with the "rbu_control" column set to contain integer value 0. The
** other columns should be set to the values that make up the new record 
** to insert. 
**
** If the target database table has an INTEGER PRIMARY KEY, it is not 
** possible to insert a NULL value into the IPK column. Attempting to 
** do so results in an SQLITE_MISMATCH error.
**
** For each row to DELETE from the target database as part of the RBU 
** update, the corresponding data_% table should contain a single record
** with the "rbu_control" column set to contain integer value 1. The
** real primary key values of the row to delete should be stored in the
** corresponding columns of the data_% table. The values stored in the
** other columns are not used.
**
** For each row to UPDATE from the target database as part of the RBU 
** update, the corresponding data_% table should contain a single record
** with the "rbu_control" column set to contain a value of type text.
** The real primary key values identifying the row to update should be 
** stored in the corresponding columns of the data_% table row, as should
** the new values of all columns being update. The text value in the 
** "rbu_control" column must contain the same number of characters as
** there are columns in the target database table, and must consist entirely
** of 'x' and '.' characters (or in some special cases 'd' - see below). For 
** each column that is being updated, the corresponding character is set to
** 'x'. For those that remain as they are, the corresponding character of the
** rbu_control value should be set to '.'. For example, given the tables 
** above, the update statement:
**
**   UPDATE t1 SET c = 'usa' WHERE a = 4;
**
** is represented by the data_t1 row created by:
**
**   INSERT INTO data_t1(a, b, c, rbu_control) VALUES(4, NULL, 'usa', '..x');
**
** Instead of an 'x' character, characters of the rbu_control value specified
** for UPDATEs may also be set to 'd'. In this case, instead of updating the
** target table with the value stored in the corresponding data_% column, the
** user-defined SQL function "rbu_delta()" is invoked and the result stored in
** the target table column. rbu_delta() is invoked with two arguments - the
** original value currently stored in the target table column and the 
** value specified in the data_xxx table.
**
** For example, this row:
**
**   INSERT INTO data_t1(a, b, c, rbu_control) VALUES(4, NULL, 'usa', '..d');
**
** is similar to an UPDATE statement such as: 
**
**   UPDATE t1 SET c = rbu_delta(c, 'usa') WHERE a = 4;
**
** If the target database table is a virtual table or a table with no PRIMARY
** KEY, the rbu_control value should not include a character corresponding 
** to the rbu_rowid value. For example, this:
**
**   INSERT INTO data_ft1(a, b, rbu_rowid, rbu_control) 
**       VALUES(NULL, 'usa', 12, '.x');
**
** causes a result similar to:
**
**   UPDATE ft1 SET b = 'usa' WHERE rowid = 12;
**
** The data_xxx tables themselves should have no PRIMARY KEY declarations.
** However, RBU is more efficient if reading the rows in from each data_xxx
** table in "rowid" order is roughly the same as reading them sorted by
** the PRIMARY KEY of the corresponding target database table. In other 
** words, rows should be sorted using the destination table PRIMARY KEY 
** fields before they are inserted into the data_xxx tables.
**
** USAGE
**
** The API declared below allows an application to apply an RBU update 
** stored on disk to an existing target database. Essentially, the 
** application:
**
**     1) Opens an RBU handle using the sqlite3rbu_open() function.
**
**     2) Registers any required virtual table modules with the database
**        handle returned by sqlite3rbu_db(). Also, if required, register
**        the rbu_delta() implementation.
**
**     3) Calls the sqlite3rbu_step() function one or more times on
**        the new handle. Each call to sqlite3rbu_step() performs a single
**        b-tree operation, so thousands of calls may be required to apply 
**        a complete update.
**
**     4) Calls sqlite3rbu_close() to close the RBU update handle. If
**        sqlite3rbu_step() has been called enough times to completely
**        apply the update to the target database, then the RBU database
**        is marked as fully applied. Otherwise, the state of the RBU 
**        update application is saved in the RBU database for later 
**        resumption.
**
** See comments below for more detail on APIs.
**
** If an update is only partially applied to the target database by the
** time sqlite3rbu_close() is called, various state information is saved 
** within the RBU database. This allows subsequent processes to automatically
** resume the RBU update from where it left off.
**
** To remove all RBU extension state information, returning an RBU database 
** to its original contents, it is sufficient to drop all tables that begin
** with the prefix "rbu_"
**
** DATABASE LOCKING
**
** An RBU update may not be applied to a database in WAL mode. Attempting
** to do so is an error (SQLITE_ERROR).
**
** While an RBU handle is open, a SHARED lock may be held on the target
** database file. This means it is possible for other clients to read the
** database, but not to write it.
**
** If an RBU update is started and then suspended before it is completed,
** then an external client writes to the database, then attempting to resume
** the suspended RBU update is also an error (SQLITE_BUSY).
*/

#ifndef _SQLITE3RBU_H
#define _SQLITE3RBU_H

/* #include "sqlite3.h"              ** Required for error code definitions ** */

typedef struct sqlite3rbu sqlite3rbu;

/*
** Open an RBU handle.
**
** Argument zTarget is the path to the target database. Argument zRbu is
** the path to the RBU database. Each call to this function must be matched
** by a call to sqlite3rbu_close(). When opening the databases, RBU passes
** the SQLITE_CONFIG_URI flag to sqlite3_open_v2(). So if either zTarget
** or zRbu begin with "file:", it will be interpreted as an SQLite 
** database URI, not a regular file name.
**
** If the zState argument is passed a NULL value, the RBU extension stores 
** the current state of the update (how many rows have been updated, which 
** indexes are yet to be updated etc.) within the RBU database itself. This
** can be convenient, as it means that the RBU application does not need to
** organize removing a separate state file after the update is concluded. 
** Or, if zState is non-NULL, it must be a path to a database file in which 
** the RBU extension can store the state of the update.
**
** When resuming an RBU update, the zState argument must be passed the same
** value as when the RBU update was started.
**
** Once the RBU update is finished, the RBU extension does not 
** automatically remove any zState database file, even if it created it.
**
** By default, RBU uses the default VFS to access the files on disk. To
** use a VFS other than the default, an SQLite "file:" URI containing a
** "vfs=..." option may be passed as the zTarget option.
**
** IMPORTANT NOTE FOR ZIPVFS USERS: The RBU extension works with all of
** SQLite's built-in VFSs, including the multiplexor VFS. However it does
** not work out of the box with zipvfs. Refer to the comment describing
** the zipvfs_create_vfs() API below for details on using RBU with zipvfs.
*/
SQLITE_API sqlite3rbu *SQLITE_STDCALL sqlite3rbu_open(
  const char *zTarget, 
  const char *zRbu,
  const char *zState
);

/*
** Internally, each RBU connection uses a separate SQLite database 
** connection to access the target and rbu update databases. This
** API allows the application direct access to these database handles.
**
** The first argument passed to this function must be a valid, open, RBU
** handle. The second argument should be passed zero to access the target
** database handle, or non-zero to access the rbu update database handle.
** Accessing the underlying database handles may be useful in the
** following scenarios:
**
**   * If any target tables are virtual tables, it may be necessary to
**     call sqlite3_create_module() on the target database handle to 
**     register the required virtual table implementations.
**
**   * If the data_xxx tables in the RBU source database are virtual 
**     tables, the application may need to call sqlite3_create_module() on
**     the rbu update db handle to any required virtual table
**     implementations.
**
**   * If the application uses the "rbu_delta()" feature described above,
**     it must use sqlite3_create_function() or similar to register the
**     rbu_delta() implementation with the target database handle.
**
** If an error has occurred, either while opening or stepping the RBU object,
** this function may return NULL. The error code and message may be collected
** when sqlite3rbu_close() is called.
*/
SQLITE_API sqlite3 *SQLITE_STDCALL sqlite3rbu_db(sqlite3rbu*, int bRbu);

/*
** Do some work towards applying the RBU update to the target db. 
**
** Return SQLITE_DONE if the update has been completely applied, or 
** SQLITE_OK if no error occurs but there remains work to do to apply
** the RBU update. If an error does occur, some other error code is 
** returned. 
**
** Once a call to sqlite3rbu_step() has returned a value other than
** SQLITE_OK, all subsequent calls on the same RBU handle are no-ops
** that immediately return the same value.
*/
SQLITE_API int SQLITE_STDCALL sqlite3rbu_step(sqlite3rbu *pRbu);

/*
** Close an RBU handle. 
**
** If the RBU update has been completely applied, mark the RBU database
** as fully applied. Otherwise, assuming no error has occurred, save the
** current state of the RBU update appliation to the RBU database.
**
** If an error has already occurred as part of an sqlite3rbu_step()
** or sqlite3rbu_open() call, or if one occurs within this function, an
** SQLite error code is returned. Additionally, *pzErrmsg may be set to
** point to a buffer containing a utf-8 formatted English language error
** message. It is the responsibility of the caller to eventually free any 
** such buffer using sqlite3_free().
**
** Otherwise, if no error occurs, this function returns SQLITE_OK if the
** update has been partially applied, or SQLITE_DONE if it has been 
** completely applied.
*/
SQLITE_API int SQLITE_STDCALL sqlite3rbu_close(sqlite3rbu *pRbu, char **pzErrmsg);

/*
** Return the total number of key-value operations (inserts, deletes or 
** updates) that have been performed on the target database since the
** current RBU update was started.
*/
SQLITE_API sqlite3_int64 SQLITE_STDCALL sqlite3rbu_progress(sqlite3rbu *pRbu);

/*
** Create an RBU VFS named zName that accesses the underlying file-system
** via existing VFS zParent. Or, if the zParent parameter is passed NULL, 
** then the new RBU VFS uses the default system VFS to access the file-system.
** The new object is registered as a non-default VFS with SQLite before 
** returning.
**
** Part of the RBU implementation uses a custom VFS object. Usually, this
** object is created and deleted automatically by RBU. 
**
** The exception is for applications that also use zipvfs. In this case,
** the custom VFS must be explicitly created by the user before the RBU
** handle is opened. The RBU VFS should be installed so that the zipvfs
** VFS uses the RBU VFS, which in turn uses any other VFS layers in use 
** (for example multiplexor) to access the file-system. For example,
** to assemble an RBU enabled VFS stack that uses both zipvfs and 
** multiplexor (error checking omitted):
**
**     // Create a VFS named "multiplex" (not the default).
**     sqlite3_multiplex_initialize(0, 0);
**
**     // Create an rbu VFS named "rbu" that uses multiplexor. If the
**     // second argument were replaced with NULL, the "rbu" VFS would
**     // access the file-system via the system default VFS, bypassing the
**     // multiplexor.
**     sqlite3rbu_create_vfs("rbu", "multiplex");
**
**     // Create a zipvfs VFS named "zipvfs" that uses rbu.
**     zipvfs_create_vfs_v3("zipvfs", "rbu", 0, xCompressorAlgorithmDetector);
**
**     // Make zipvfs the default VFS.
**     sqlite3_vfs_register(sqlite3_vfs_find("zipvfs"), 1);
**
** Because the default VFS created above includes a RBU functionality, it
** may be used by RBU clients. Attempting to use RBU with a zipvfs VFS stack
** that does not include the RBU layer results in an error.
**
** The overhead of adding the "rbu" VFS to the system is negligible for 
** non-RBU users. There is no harm in an application accessing the 
** file-system via "rbu" all the time, even if it only uses RBU functionality 
** occasionally.
*/
SQLITE_API int SQLITE_STDCALL sqlite3rbu_create_vfs(const char *zName, const char *zParent);

/*
** Deregister and destroy an RBU vfs created by an earlier call to
** sqlite3rbu_create_vfs().
**
** VFS objects are not reference counted. If a VFS object is destroyed
** before all database handles that use it have been closed, the results
** are undefined.
*/
SQLITE_API void SQLITE_STDCALL sqlite3rbu_destroy_vfs(const char *zName);

#endif /* _SQLITE3RBU_H */

/************** End of sqlite3rbu.h ******************************************/
/************** Continuing where we left off in sqlite3rbu.c *****************/

/* Maximum number of prepared UPDATE statements held by this module */
#define SQLITE_RBU_UPDATE_CACHESIZE 16

/*
** Swap two objects of type TYPE.
*/
#if !defined(SQLITE_AMALGAMATION)
# define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
#endif

/*
** The rbu_state table is used to save the state of a partially applied
** update so that it can be resumed later. The table consists of integer
** keys mapped to values as follows:
**
** RBU_STATE_STAGE:
**   May be set to integer values 1, 2, 4 or 5. As follows:
**       1: the *-rbu file is currently under construction.
**       2: the *-rbu file has been constructed, but not yet moved 
**          to the *-wal path.
**       4: the checkpoint is underway.
**       5: the rbu update has been checkpointed.
**
** RBU_STATE_TBL:
**   Only valid if STAGE==1. The target database name of the table 
**   currently being written.
**
** RBU_STATE_IDX:
**   Only valid if STAGE==1. The target database name of the index 
**   currently being written, or NULL if the main table is currently being
**   updated.
**
** RBU_STATE_ROW:
**   Only valid if STAGE==1. Number of rows already processed for the current
**   table/index.
**
** RBU_STATE_PROGRESS:
**   Trbul number of sqlite3rbu_step() calls made so far as part of this
**   rbu update.
**
** RBU_STATE_CKPT:
**   Valid if STAGE==4. The 64-bit checksum associated with the wal-index
**   header created by recovering the *-wal file. This is used to detect
**   cases when another client appends frames to the *-wal file in the
**   middle of an incremental checkpoint (an incremental checkpoint cannot
**   be continued if this happens).
**
** RBU_STATE_COOKIE:
**   Valid if STAGE==1. The current change-counter cookie value in the 
**   target db file.
**
** RBU_STATE_OALSZ:
**   Valid if STAGE==1. The size in bytes of the *-oal file.
*/
#define RBU_STATE_STAGE       1
#define RBU_STATE_TBL         2
#define RBU_STATE_IDX         3
#define RBU_STATE_ROW         4
#define RBU_STATE_PROGRESS    5
#define RBU_STATE_CKPT        6
#define RBU_STATE_COOKIE      7
#define RBU_STATE_OALSZ       8

#define RBU_STAGE_OAL         1
#define RBU_STAGE_MOVE        2
#define RBU_STAGE_CAPTURE     3
#define RBU_STAGE_CKPT        4
#define RBU_STAGE_DONE        5


#define RBU_CREATE_STATE \
  "CREATE TABLE IF NOT EXISTS %s.rbu_state(k INTEGER PRIMARY KEY, v)"

typedef struct RbuFrame RbuFrame;
typedef struct RbuObjIter RbuObjIter;
typedef struct RbuState RbuState;
typedef struct rbu_vfs rbu_vfs;
typedef struct rbu_file rbu_file;
typedef struct RbuUpdateStmt RbuUpdateStmt;

#if !defined(SQLITE_AMALGAMATION)
typedef unsigned int u32;
typedef unsigned char u8;
typedef sqlite3_int64 i64;
#endif

/*
** These values must match the values defined in wal.c for the equivalent
** locks. These are not magic numbers as they are part of the SQLite file
** format.
*/
#define WAL_LOCK_WRITE  0
#define WAL_LOCK_CKPT   1
#define WAL_LOCK_READ0  3

/*
** A structure to store values read from the rbu_state table in memory.
*/
struct RbuState {
  int eStage;
  char *zTbl;
  char *zIdx;
  i64 iWalCksum;
  int nRow;
  i64 nProgress;
  u32 iCookie;
  i64 iOalSz;
};

struct RbuUpdateStmt {
  char *zMask;                    /* Copy of update mask used with pUpdate */
  sqlite3_stmt *pUpdate;          /* Last update statement (or NULL) */
  RbuUpdateStmt *pNext;
};

/*
** An iterator of this type is used to iterate through all objects in
** the target database that require updating. For each such table, the
** iterator visits, in order:
**
**     * the table itself, 
**     * each index of the table (zero or more points to visit), and
**     * a special "cleanup table" state.
**
** abIndexed:
**   If the table has no indexes on it, abIndexed is set to NULL. Otherwise,
**   it points to an array of flags nTblCol elements in size. The flag is
**   set for each column that is either a part of the PK or a part of an
**   index. Or clear otherwise.
**   
*/
struct RbuObjIter {
  sqlite3_stmt *pTblIter;         /* Iterate through tables */
  sqlite3_stmt *pIdxIter;         /* Index iterator */
  int nTblCol;                    /* Size of azTblCol[] array */
  char **azTblCol;                /* Array of unquoted target column names */
  char **azTblType;               /* Array of target column types */
  int *aiSrcOrder;                /* src table col -> target table col */
  u8 *abTblPk;                    /* Array of flags, set on target PK columns */
  u8 *abNotNull;                  /* Array of flags, set on NOT NULL columns */
  u8 *abIndexed;                  /* Array of flags, set on indexed & PK cols */
  int eType;                      /* Table type - an RBU_PK_XXX value */

  /* Output variables. zTbl==0 implies EOF. */
  int bCleanup;                   /* True in "cleanup" state */
  const char *zTbl;               /* Name of target db table */
  const char *zIdx;               /* Name of target db index (or null) */
  int iTnum;                      /* Root page of current object */
  int iPkTnum;                    /* If eType==EXTERNAL, root of PK index */
  int bUnique;                    /* Current index is unique */

  /* Statements created by rbuObjIterPrepareAll() */
  int nCol;                       /* Number of columns in current object */
  sqlite3_stmt *pSelect;          /* Source data */
  sqlite3_stmt *pInsert;          /* Statement for INSERT operations */
  sqlite3_stmt *pDelete;          /* Statement for DELETE ops */
  sqlite3_stmt *pTmpInsert;       /* Insert into rbu_tmp_$zTbl */

  /* Last UPDATE used (for PK b-tree updates only), or NULL. */
  RbuUpdateStmt *pRbuUpdate;
};

/*
** Values for RbuObjIter.eType
**
**     0: Table does not exist (error)
**     1: Table has an implicit rowid.
**     2: Table has an explicit IPK column.
**     3: Table has an external PK index.
**     4: Table is WITHOUT ROWID.
**     5: Table is a virtual table.
*/
#define RBU_PK_NOTABLE        0
#define RBU_PK_NONE           1
#define RBU_PK_IPK            2
#define RBU_PK_EXTERNAL       3
#define RBU_PK_WITHOUT_ROWID  4
#define RBU_PK_VTAB           5


/*
** Within the RBU_STAGE_OAL stage, each call to sqlite3rbu_step() performs
** one of the following operations.
*/
#define RBU_INSERT     1          /* Insert on a main table b-tree */
#define RBU_DELETE     2          /* Delete a row from a main table b-tree */
#define RBU_IDX_DELETE 3          /* Delete a row from an aux. index b-tree */
#define RBU_IDX_INSERT 4          /* Insert on an aux. index b-tree */
#define RBU_UPDATE     5          /* Update a row in a main table b-tree */


/*
** A single step of an incremental checkpoint - frame iWalFrame of the wal
** file should be copied to page iDbPage of the database file.
*/
struct RbuFrame {
  u32 iDbPage;
  u32 iWalFrame;
};

/*
** RBU handle.
*/
struct sqlite3rbu {
  int eStage;                     /* Value of RBU_STATE_STAGE field */
  sqlite3 *dbMain;                /* target database handle */
  sqlite3 *dbRbu;                 /* rbu database handle */
  char *zTarget;                  /* Path to target db */
  char *zRbu;                     /* Path to rbu db */
  char *zState;                   /* Path to state db (or NULL if zRbu) */
  char zStateDb[5];               /* Db name for state ("stat" or "main") */
  int rc;                         /* Value returned by last rbu_step() call */
  char *zErrmsg;                  /* Error message if rc!=SQLITE_OK */
  int nStep;                      /* Rows processed for current object */
  int nProgress;                  /* Rows processed for all objects */
  RbuObjIter objiter;             /* Iterator for skipping through tbl/idx */
  const char *zVfsName;           /* Name of automatically created rbu vfs */
  rbu_file *pTargetFd;            /* File handle open on target db */
  i64 iOalSz;

  /* The following state variables are used as part of the incremental
  ** checkpoint stage (eStage==RBU_STAGE_CKPT). See comments surrounding
  ** function rbuSetupCheckpoint() for details.  */
  u32 iMaxFrame;                  /* Largest iWalFrame value in aFrame[] */
  u32 mLock;
  int nFrame;                     /* Entries in aFrame[] array */
  int nFrameAlloc;                /* Allocated size of aFrame[] array */
  RbuFrame *aFrame;
  int pgsz;
  u8 *aBuf;
  i64 iWalCksum;
};

/*
** An rbu VFS is implemented using an instance of this structure.
*/
struct rbu_vfs {
  sqlite3_vfs base;               /* rbu VFS shim methods */
  sqlite3_vfs *pRealVfs;          /* Underlying VFS */
  sqlite3_mutex *mutex;           /* Mutex to protect pMain */
  rbu_file *pMain;                /* Linked list of main db files */
};

/*
** Each file opened by an rbu VFS is represented by an instance of
** the following structure.
*/
struct rbu_file {
  sqlite3_file base;              /* sqlite3_file methods */
  sqlite3_file *pReal;            /* Underlying file handle */
  rbu_vfs *pRbuVfs;               /* Pointer to the rbu_vfs object */
  sqlite3rbu *pRbu;               /* Pointer to rbu object (rbu target only) */

  int openFlags;                  /* Flags this file was opened with */
  u32 iCookie;                    /* Cookie value for main db files */
  u8 iWriteVer;                   /* "write-version" value for main db files */

  int nShm;                       /* Number of entries in apShm[] array */
  char **apShm;                   /* Array of mmap'd *-shm regions */
  char *zDel;                     /* Delete this when closing file */

  const char *zWal;               /* Wal filename for this main db file */
  rbu_file *pWalFd;               /* Wal file descriptor for this main db */
  rbu_file *pMainNext;            /* Next MAIN_DB file */
};


/*
** Prepare the SQL statement in buffer zSql against database handle db.
** If successful, set *ppStmt to point to the new statement and return
** SQLITE_OK. 
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    rc = prepareAndCollectError(db, ppStmt, pzErrmsg, zSql);
    sqlite3_free(zSql);
  }
  return rc;
}

/*
** Free the OtaObjIter.azTblCol[] and OtaObjIter.abTblPk[] arrays allocated
** by an earlier call to otaObjIterCacheTableInfo().
*/
static void otaObjIterFreeCols(OtaObjIter *pIter){
  int i;
  for(i=0; i<pIter->nTblCol; i++){
    sqlite3_free(pIter->azTblCol[i]);
    sqlite3_free(pIter->azTblType[i]);
  }
  sqlite3_free(pIter->azTblCol);
  pIter->azTblCol = 0;
  pIter->azTblType = 0;
  pIter->aiSrcOrder = 0;
  pIter->abTblPk = 0;
  pIter->abNotNull = 0;
  pIter->nTblCol = 0;
  pIter->eType = 0;               /* Invalid value */
}

/*
** Finalize all statements and free all allocations that are specific to
** the current object (table/index pair).
*/
static void otaObjIterClearStatements(OtaObjIter *pIter){
  OtaUpdateStmt *pUp;

  sqlite3_finalize(pIter->pSelect);
  sqlite3_finalize(pIter->pInsert);
  sqlite3_finalize(pIter->pDelete);
  sqlite3_finalize(pIter->pTmpInsert);
  pUp = pIter->pOtaUpdate;
  while( pUp ){
    OtaUpdateStmt *pTmp = pUp->pNext;
    sqlite3_finalize(pUp->pUpdate);
    sqlite3_free(pUp);
    pUp = pTmp;
  }
  
  pIter->pSelect = 0;
  pIter->pInsert = 0;
  pIter->pDelete = 0;
  pIter->pOtaUpdate = 0;
  pIter->pTmpInsert = 0;
  pIter->nCol = 0;
}

/*
** Clean up any resources allocated as part of the iterator object passed
** as the only argument.
*/
static void otaObjIterFinalize(OtaObjIter *pIter){
  otaObjIterClearStatements(pIter);
  sqlite3_finalize(pIter->pTblIter);
  sqlite3_finalize(pIter->pIdxIter);
  otaObjIterFreeCols(pIter);
  memset(pIter, 0, sizeof(OtaObjIter));
}

/*
** Advance the iterator to the next position.
**
** If no error occurs, SQLITE_OK is returned and the iterator is left 
** pointing to the next entry. Otherwise, an error code and message is 
** left in the OTA handle passed as the first argument. A copy of the 
** error code is returned.
*/
static int otaObjIterNext(sqlite3ota *p, OtaObjIter *pIter){
  int rc = p->rc;
  if( rc==SQLITE_OK ){

    /* Free any SQLite statements used while processing the previous object */ 
    otaObjIterClearStatements(pIter);
    if( pIter->zIdx==0 ){
      rc = sqlite3_exec(p->dbMain,
          "DROP TRIGGER IF EXISTS temp.ota_insert_tr;"
          "DROP TRIGGER IF EXISTS temp.ota_update1_tr;"
          "DROP TRIGGER IF EXISTS temp.ota_update2_tr;"
          "DROP TRIGGER IF EXISTS temp.ota_delete_tr;"
          , 0, 0, &p->zErrmsg
      );
    }

    if( rc==SQLITE_OK ){
      if( pIter->bCleanup ){
        otaObjIterFreeCols(pIter);
        pIter->bCleanup = 0;
        rc = sqlite3_step(pIter->pTblIter);
        if( rc!=SQLITE_ROW ){
          rc = resetAndCollectError(pIter->pTblIter, &p->zErrmsg);
          pIter->zTbl = 0;
        }else{
          pIter->zTbl = (const char*)sqlite3_column_text(pIter->pTblIter, 0);







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    rc = prepareAndCollectError(db, ppStmt, pzErrmsg, zSql);
    sqlite3_free(zSql);
  }
  return rc;
}

/*
** Free the RbuObjIter.azTblCol[] and RbuObjIter.abTblPk[] arrays allocated
** by an earlier call to rbuObjIterCacheTableInfo().
*/
static void rbuObjIterFreeCols(RbuObjIter *pIter){
  int i;
  for(i=0; i<pIter->nTblCol; i++){
    sqlite3_free(pIter->azTblCol[i]);
    sqlite3_free(pIter->azTblType[i]);
  }
  sqlite3_free(pIter->azTblCol);
  pIter->azTblCol = 0;
  pIter->azTblType = 0;
  pIter->aiSrcOrder = 0;
  pIter->abTblPk = 0;
  pIter->abNotNull = 0;
  pIter->nTblCol = 0;
  pIter->eType = 0;               /* Invalid value */
}

/*
** Finalize all statements and free all allocations that are specific to
** the current object (table/index pair).
*/
static void rbuObjIterClearStatements(RbuObjIter *pIter){
  RbuUpdateStmt *pUp;

  sqlite3_finalize(pIter->pSelect);
  sqlite3_finalize(pIter->pInsert);
  sqlite3_finalize(pIter->pDelete);
  sqlite3_finalize(pIter->pTmpInsert);
  pUp = pIter->pRbuUpdate;
  while( pUp ){
    RbuUpdateStmt *pTmp = pUp->pNext;
    sqlite3_finalize(pUp->pUpdate);
    sqlite3_free(pUp);
    pUp = pTmp;
  }
  
  pIter->pSelect = 0;
  pIter->pInsert = 0;
  pIter->pDelete = 0;
  pIter->pRbuUpdate = 0;
  pIter->pTmpInsert = 0;
  pIter->nCol = 0;
}

/*
** Clean up any resources allocated as part of the iterator object passed
** as the only argument.
*/
static void rbuObjIterFinalize(RbuObjIter *pIter){
  rbuObjIterClearStatements(pIter);
  sqlite3_finalize(pIter->pTblIter);
  sqlite3_finalize(pIter->pIdxIter);
  rbuObjIterFreeCols(pIter);
  memset(pIter, 0, sizeof(RbuObjIter));
}

/*
** Advance the iterator to the next position.
**
** If no error occurs, SQLITE_OK is returned and the iterator is left 
** pointing to the next entry. Otherwise, an error code and message is 
** left in the RBU handle passed as the first argument. A copy of the 
** error code is returned.
*/
static int rbuObjIterNext(sqlite3rbu *p, RbuObjIter *pIter){
  int rc = p->rc;
  if( rc==SQLITE_OK ){

    /* Free any SQLite statements used while processing the previous object */ 
    rbuObjIterClearStatements(pIter);
    if( pIter->zIdx==0 ){
      rc = sqlite3_exec(p->dbMain,
          "DROP TRIGGER IF EXISTS temp.rbu_insert_tr;"
          "DROP TRIGGER IF EXISTS temp.rbu_update1_tr;"
          "DROP TRIGGER IF EXISTS temp.rbu_update2_tr;"
          "DROP TRIGGER IF EXISTS temp.rbu_delete_tr;"
          , 0, 0, &p->zErrmsg
      );
    }

    if( rc==SQLITE_OK ){
      if( pIter->bCleanup ){
        rbuObjIterFreeCols(pIter);
        pIter->bCleanup = 0;
        rc = sqlite3_step(pIter->pTblIter);
        if( rc!=SQLITE_ROW ){
          rc = resetAndCollectError(pIter->pTblIter, &p->zErrmsg);
          pIter->zTbl = 0;
        }else{
          pIter->zTbl = (const char*)sqlite3_column_text(pIter->pTblIter, 0);
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          }
        }
      }
    }
  }

  if( rc!=SQLITE_OK ){
    otaObjIterFinalize(pIter);
    p->rc = rc;
  }
  return rc;
}

/*
** Initialize the iterator structure passed as the second argument.
**
** If no error occurs, SQLITE_OK is returned and the iterator is left 
** pointing to the first entry. Otherwise, an error code and message is 
** left in the OTA handle passed as the first argument. A copy of the 
** error code is returned.
*/
static int otaObjIterFirst(sqlite3ota *p, OtaObjIter *pIter){
  int rc;
  memset(pIter, 0, sizeof(OtaObjIter));

  rc = prepareAndCollectError(p->dbOta, &pIter->pTblIter, &p->zErrmsg, 
      "SELECT substr(name, 6) FROM sqlite_master "
      "WHERE type='table' AND name LIKE 'data_%'"
  );

  if( rc==SQLITE_OK ){
    rc = prepareAndCollectError(p->dbMain, &pIter->pIdxIter, &p->zErrmsg,
        "SELECT name, rootpage, sql IS NULL OR substr(8, 6)=='UNIQUE' "
        "  FROM main.sqlite_master "
        "  WHERE type='index' AND tbl_name = ?"
    );
  }

  pIter->bCleanup = 1;
  p->rc = rc;
  return otaObjIterNext(p, pIter);
}

/*
** This is a wrapper around "sqlite3_mprintf(zFmt, ...)". If an OOM occurs,
** an error code is stored in the OTA handle passed as the first argument.
**
** If an error has already occurred (p->rc is already set to something other
** than SQLITE_OK), then this function returns NULL without modifying the
** stored error code. In this case it still calls sqlite3_free() on any 
** printf() parameters associated with %z conversions.
*/
static char *otaMPrintf(sqlite3ota *p, const char *zFmt, ...){
  char *zSql = 0;
  va_list ap;
  va_start(ap, zFmt);
  zSql = sqlite3_vmprintf(zFmt, ap);
  if( p->rc==SQLITE_OK ){
    if( zSql==0 ) p->rc = SQLITE_NOMEM;
  }else{
    sqlite3_free(zSql);
    zSql = 0;
  }
  va_end(ap);
  return zSql;
}

/*
** Argument zFmt is a sqlite3_mprintf() style format string. The trailing
** arguments are the usual subsitution values. This function performs
** the printf() style substitutions and executes the result as an SQL
** statement on the OTA handles database.
**
** If an error occurs, an error code and error message is stored in the
** OTA handle. If an error has already occurred when this function is
** called, it is a no-op.
*/
static int otaMPrintfExec(sqlite3ota *p, sqlite3 *db, const char *zFmt, ...){
  va_list ap;
  va_start(ap, zFmt);
  char *zSql = sqlite3_vmprintf(zFmt, ap);
  if( p->rc==SQLITE_OK ){
    if( zSql==0 ){
      p->rc = SQLITE_NOMEM;
    }else{
      p->rc = sqlite3_exec(db, zSql, 0, 0, &p->zErrmsg);
    }
  }
  sqlite3_free(zSql);
  va_end(ap);
  return p->rc;
}

/*
** Attempt to allocate and return a pointer to a zeroed block of nByte 
** bytes. 
**
** If an error (i.e. an OOM condition) occurs, return NULL and leave an 
** error code in the ota handle passed as the first argument. Or, if an 
** error has already occurred when this function is called, return NULL 
** immediately without attempting the allocation or modifying the stored
** error code.
*/
static void *otaMalloc(sqlite3ota *p, int nByte){
  void *pRet = 0;
  if( p->rc==SQLITE_OK ){
    assert( nByte>0 );
    pRet = sqlite3_malloc(nByte);
    if( pRet==0 ){
      p->rc = SQLITE_NOMEM;
    }else{
      memset(pRet, 0, nByte);
    }
  }
  return pRet;
}


/*
** Allocate and zero the pIter->azTblCol[] and abTblPk[] arrays so that
** there is room for at least nCol elements. If an OOM occurs, store an
** error code in the OTA handle passed as the first argument.
*/
static void otaAllocateIterArrays(sqlite3ota *p, OtaObjIter *pIter, int nCol){
  int nByte = (2*sizeof(char*) + sizeof(int) + 3*sizeof(u8)) * nCol;
  char **azNew;

  azNew = (char**)otaMalloc(p, nByte);
  if( azNew ){
    pIter->azTblCol = azNew;
    pIter->azTblType = &azNew[nCol];
    pIter->aiSrcOrder = (int*)&pIter->azTblType[nCol];
    pIter->abTblPk = (u8*)&pIter->aiSrcOrder[nCol];
    pIter->abNotNull = (u8*)&pIter->abTblPk[nCol];
    pIter->abIndexed = (u8*)&pIter->abNotNull[nCol];
  }
}

/*
** The first argument must be a nul-terminated string. This function
** returns a copy of the string in memory obtained from sqlite3_malloc().
** It is the responsibility of the caller to eventually free this memory
** using sqlite3_free().
**
** If an OOM condition is encountered when attempting to allocate memory,
** output variable (*pRc) is set to SQLITE_NOMEM before returning. Otherwise,
** if the allocation succeeds, (*pRc) is left unchanged.
*/
static char *otaStrndup(const char *zStr, int *pRc){
  char *zRet = 0;

  assert( *pRc==SQLITE_OK );
  if( zStr ){
    int nCopy = strlen(zStr) + 1;
    zRet = (char*)sqlite3_malloc(nCopy);
    if( zRet ){
      memcpy(zRet, zStr, nCopy);
    }else{
      *pRc = SQLITE_NOMEM;
    }
  }

  return zRet;
}

/*
** Finalize the statement passed as the second argument.
**
** If the sqlite3_finalize() call indicates that an error occurs, and the
** ota handle error code is not already set, set the error code and error
** message accordingly.
*/
static void otaFinalize(sqlite3ota *p, sqlite3_stmt *pStmt){
  sqlite3 *db = sqlite3_db_handle(pStmt);
  int rc = sqlite3_finalize(pStmt);
  if( p->rc==SQLITE_OK && rc!=SQLITE_OK ){
    p->rc = rc;
    p->zErrmsg = sqlite3_mprintf("%s", sqlite3_errmsg(db));
  }
}

/* Determine the type of a table.
**
**   peType is of type (int*), a pointer to an output parameter of type
**   (int). This call sets the output parameter as follows, depending
**   on the type of the table specified by parameters dbName and zTbl.
**
**     OTA_PK_NOTABLE:       No such table.
**     OTA_PK_NONE:          Table has an implicit rowid.
**     OTA_PK_IPK:           Table has an explicit IPK column.
**     OTA_PK_EXTERNAL:      Table has an external PK index.
**     OTA_PK_WITHOUT_ROWID: Table is WITHOUT ROWID.
**     OTA_PK_VTAB:          Table is a virtual table.
**
**   Argument *piPk is also of type (int*), and also points to an output
**   parameter. Unless the table has an external primary key index 
**   (i.e. unless *peType is set to 3), then *piPk is set to zero. Or,
**   if the table does have an external primary key index, then *piPk
**   is set to the root page number of the primary key index before
**   returning.
**
** ALGORITHM:
**
**   if( no entry exists in sqlite_master ){
**     return OTA_PK_NOTABLE
**   }else if( sql for the entry starts with "CREATE VIRTUAL" ){
**     return OTA_PK_VTAB
**   }else if( "PRAGMA index_list()" for the table contains a "pk" index ){
**     if( the index that is the pk exists in sqlite_master ){
**       *piPK = rootpage of that index.
**       return OTA_PK_EXTERNAL
**     }else{
**       return OTA_PK_WITHOUT_ROWID
**     }
**   }else if( "PRAGMA table_info()" lists one or more "pk" columns ){
**     return OTA_PK_IPK
**   }else{
**     return OTA_PK_NONE
**   }
*/
static void otaTableType(
  sqlite3ota *p,
  const char *zTab,
  int *peType,
  int *piTnum,
  int *piPk
){
  /*
  ** 0) SELECT count(*) FROM sqlite_master where name=%Q AND IsVirtual(%Q)
  ** 1) PRAGMA index_list = ?
  ** 2) SELECT count(*) FROM sqlite_master where name=%Q 
  ** 3) PRAGMA table_info = ?
  */
  sqlite3_stmt *aStmt[4] = {0, 0, 0, 0};

  *peType = OTA_PK_NOTABLE;
  *piPk = 0;

  assert( p->rc==SQLITE_OK );
  p->rc = prepareFreeAndCollectError(p->dbMain, &aStmt[0], &p->zErrmsg, 
    sqlite3_mprintf(
          "SELECT (sql LIKE 'create virtual%%'), rootpage"
          "  FROM sqlite_master"
          " WHERE name=%Q", zTab
  ));
  if( p->rc!=SQLITE_OK || sqlite3_step(aStmt[0])!=SQLITE_ROW ){
    /* Either an error, or no such table. */
    goto otaTableType_end;
  }
  if( sqlite3_column_int(aStmt[0], 0) ){
    *peType = OTA_PK_VTAB;                     /* virtual table */
    goto otaTableType_end;
  }
  *piTnum = sqlite3_column_int(aStmt[0], 1);

  p->rc = prepareFreeAndCollectError(p->dbMain, &aStmt[1], &p->zErrmsg, 
    sqlite3_mprintf("PRAGMA index_list=%Q",zTab)
  );
  if( p->rc ) goto otaTableType_end;
  while( sqlite3_step(aStmt[1])==SQLITE_ROW ){
    const u8 *zOrig = sqlite3_column_text(aStmt[1], 3);
    const u8 *zIdx = sqlite3_column_text(aStmt[1], 1);
    if( zOrig && zIdx && zOrig[0]=='p' ){
      p->rc = prepareFreeAndCollectError(p->dbMain, &aStmt[2], &p->zErrmsg, 
          sqlite3_mprintf(
            "SELECT rootpage FROM sqlite_master WHERE name = %Q", zIdx
      ));
      if( p->rc==SQLITE_OK ){
        if( sqlite3_step(aStmt[2])==SQLITE_ROW ){
          *piPk = sqlite3_column_int(aStmt[2], 0);
          *peType = OTA_PK_EXTERNAL;
        }else{
          *peType = OTA_PK_WITHOUT_ROWID;
        }
      }
      goto otaTableType_end;
    }
  }

  p->rc = prepareFreeAndCollectError(p->dbMain, &aStmt[3], &p->zErrmsg, 
    sqlite3_mprintf("PRAGMA table_info=%Q",zTab)
  );
  if( p->rc==SQLITE_OK ){
    while( sqlite3_step(aStmt[3])==SQLITE_ROW ){
      if( sqlite3_column_int(aStmt[3],5)>0 ){
        *peType = OTA_PK_IPK;                /* explicit IPK column */
        goto otaTableType_end;
      }
    }
    *peType = OTA_PK_NONE;
  }

otaTableType_end: {
    int i;
    for(i=0; i<sizeof(aStmt)/sizeof(aStmt[0]); i++){
      otaFinalize(p, aStmt[i]);
    }
  }
}

/*
** This is a helper function for otaObjIterCacheTableInfo(). It populates
** the pIter->abIndexed[] array.
*/
static void otaObjIterCacheIndexedCols(sqlite3ota *p, OtaObjIter *pIter){
  sqlite3_stmt *pList = 0;
  int bIndex = 0;

  if( p->rc==SQLITE_OK ){
    memcpy(pIter->abIndexed, pIter->abTblPk, sizeof(u8)*pIter->nTblCol);
    p->rc = prepareFreeAndCollectError(p->dbMain, &pList, &p->zErrmsg,
        sqlite3_mprintf("PRAGMA main.index_list = %Q", pIter->zTbl)







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          }
        }
      }
    }
  }

  if( rc!=SQLITE_OK ){
    rbuObjIterFinalize(pIter);
    p->rc = rc;
  }
  return rc;
}

/*
** Initialize the iterator structure passed as the second argument.
**
** If no error occurs, SQLITE_OK is returned and the iterator is left 
** pointing to the first entry. Otherwise, an error code and message is 
** left in the RBU handle passed as the first argument. A copy of the 
** error code is returned.
*/
static int rbuObjIterFirst(sqlite3rbu *p, RbuObjIter *pIter){
  int rc;
  memset(pIter, 0, sizeof(RbuObjIter));

  rc = prepareAndCollectError(p->dbRbu, &pIter->pTblIter, &p->zErrmsg, 
      "SELECT substr(name, 6) FROM sqlite_master "
      "WHERE type='table' AND name LIKE 'data_%'"
  );

  if( rc==SQLITE_OK ){
    rc = prepareAndCollectError(p->dbMain, &pIter->pIdxIter, &p->zErrmsg,
        "SELECT name, rootpage, sql IS NULL OR substr(8, 6)=='UNIQUE' "
        "  FROM main.sqlite_master "
        "  WHERE type='index' AND tbl_name = ?"
    );
  }

  pIter->bCleanup = 1;
  p->rc = rc;
  return rbuObjIterNext(p, pIter);
}

/*
** This is a wrapper around "sqlite3_mprintf(zFmt, ...)". If an OOM occurs,
** an error code is stored in the RBU handle passed as the first argument.
**
** If an error has already occurred (p->rc is already set to something other
** than SQLITE_OK), then this function returns NULL without modifying the
** stored error code. In this case it still calls sqlite3_free() on any 
** printf() parameters associated with %z conversions.
*/
static char *rbuMPrintf(sqlite3rbu *p, const char *zFmt, ...){
  char *zSql = 0;
  va_list ap;
  va_start(ap, zFmt);
  zSql = sqlite3_vmprintf(zFmt, ap);
  if( p->rc==SQLITE_OK ){
    if( zSql==0 ) p->rc = SQLITE_NOMEM;
  }else{
    sqlite3_free(zSql);
    zSql = 0;
  }
  va_end(ap);
  return zSql;
}

/*
** Argument zFmt is a sqlite3_mprintf() style format string. The trailing
** arguments are the usual subsitution values. This function performs
** the printf() style substitutions and executes the result as an SQL
** statement on the RBU handles database.
**
** If an error occurs, an error code and error message is stored in the
** RBU handle. If an error has already occurred when this function is
** called, it is a no-op.
*/
static int rbuMPrintfExec(sqlite3rbu *p, sqlite3 *db, const char *zFmt, ...){
  va_list ap;
  va_start(ap, zFmt);
  char *zSql = sqlite3_vmprintf(zFmt, ap);
  if( p->rc==SQLITE_OK ){
    if( zSql==0 ){
      p->rc = SQLITE_NOMEM;
    }else{
      p->rc = sqlite3_exec(db, zSql, 0, 0, &p->zErrmsg);
    }
  }
  sqlite3_free(zSql);
  va_end(ap);
  return p->rc;
}

/*
** Attempt to allocate and return a pointer to a zeroed block of nByte 
** bytes. 
**
** If an error (i.e. an OOM condition) occurs, return NULL and leave an 
** error code in the rbu handle passed as the first argument. Or, if an 
** error has already occurred when this function is called, return NULL 
** immediately without attempting the allocation or modifying the stored
** error code.
*/
static void *rbuMalloc(sqlite3rbu *p, int nByte){
  void *pRet = 0;
  if( p->rc==SQLITE_OK ){
    assert( nByte>0 );
    pRet = sqlite3_malloc(nByte);
    if( pRet==0 ){
      p->rc = SQLITE_NOMEM;
    }else{
      memset(pRet, 0, nByte);
    }
  }
  return pRet;
}


/*
** Allocate and zero the pIter->azTblCol[] and abTblPk[] arrays so that
** there is room for at least nCol elements. If an OOM occurs, store an
** error code in the RBU handle passed as the first argument.
*/
static void rbuAllocateIterArrays(sqlite3rbu *p, RbuObjIter *pIter, int nCol){
  int nByte = (2*sizeof(char*) + sizeof(int) + 3*sizeof(u8)) * nCol;
  char **azNew;

  azNew = (char**)rbuMalloc(p, nByte);
  if( azNew ){
    pIter->azTblCol = azNew;
    pIter->azTblType = &azNew[nCol];
    pIter->aiSrcOrder = (int*)&pIter->azTblType[nCol];
    pIter->abTblPk = (u8*)&pIter->aiSrcOrder[nCol];
    pIter->abNotNull = (u8*)&pIter->abTblPk[nCol];
    pIter->abIndexed = (u8*)&pIter->abNotNull[nCol];
  }
}

/*
** The first argument must be a nul-terminated string. This function
** returns a copy of the string in memory obtained from sqlite3_malloc().
** It is the responsibility of the caller to eventually free this memory
** using sqlite3_free().
**
** If an OOM condition is encountered when attempting to allocate memory,
** output variable (*pRc) is set to SQLITE_NOMEM before returning. Otherwise,
** if the allocation succeeds, (*pRc) is left unchanged.
*/
static char *rbuStrndup(const char *zStr, int *pRc){
  char *zRet = 0;

  assert( *pRc==SQLITE_OK );
  if( zStr ){
    int nCopy = strlen(zStr) + 1;
    zRet = (char*)sqlite3_malloc(nCopy);
    if( zRet ){
      memcpy(zRet, zStr, nCopy);
    }else{
      *pRc = SQLITE_NOMEM;
    }
  }

  return zRet;
}

/*
** Finalize the statement passed as the second argument.
**
** If the sqlite3_finalize() call indicates that an error occurs, and the
** rbu handle error code is not already set, set the error code and error
** message accordingly.
*/
static void rbuFinalize(sqlite3rbu *p, sqlite3_stmt *pStmt){
  sqlite3 *db = sqlite3_db_handle(pStmt);
  int rc = sqlite3_finalize(pStmt);
  if( p->rc==SQLITE_OK && rc!=SQLITE_OK ){
    p->rc = rc;
    p->zErrmsg = sqlite3_mprintf("%s", sqlite3_errmsg(db));
  }
}

/* Determine the type of a table.
**
**   peType is of type (int*), a pointer to an output parameter of type
**   (int). This call sets the output parameter as follows, depending
**   on the type of the table specified by parameters dbName and zTbl.
**
**     RBU_PK_NOTABLE:       No such table.
**     RBU_PK_NONE:          Table has an implicit rowid.
**     RBU_PK_IPK:           Table has an explicit IPK column.
**     RBU_PK_EXTERNAL:      Table has an external PK index.
**     RBU_PK_WITHOUT_ROWID: Table is WITHOUT ROWID.
**     RBU_PK_VTAB:          Table is a virtual table.
**
**   Argument *piPk is also of type (int*), and also points to an output
**   parameter. Unless the table has an external primary key index 
**   (i.e. unless *peType is set to 3), then *piPk is set to zero. Or,
**   if the table does have an external primary key index, then *piPk
**   is set to the root page number of the primary key index before
**   returning.
**
** ALGORITHM:
**
**   if( no entry exists in sqlite_master ){
**     return RBU_PK_NOTABLE
**   }else if( sql for the entry starts with "CREATE VIRTUAL" ){
**     return RBU_PK_VTAB
**   }else if( "PRAGMA index_list()" for the table contains a "pk" index ){
**     if( the index that is the pk exists in sqlite_master ){
**       *piPK = rootpage of that index.
**       return RBU_PK_EXTERNAL
**     }else{
**       return RBU_PK_WITHOUT_ROWID
**     }
**   }else if( "PRAGMA table_info()" lists one or more "pk" columns ){
**     return RBU_PK_IPK
**   }else{
**     return RBU_PK_NONE
**   }
*/
static void rbuTableType(
  sqlite3rbu *p,
  const char *zTab,
  int *peType,
  int *piTnum,
  int *piPk
){
  /*
  ** 0) SELECT count(*) FROM sqlite_master where name=%Q AND IsVirtual(%Q)
  ** 1) PRAGMA index_list = ?
  ** 2) SELECT count(*) FROM sqlite_master where name=%Q 
  ** 3) PRAGMA table_info = ?
  */
  sqlite3_stmt *aStmt[4] = {0, 0, 0, 0};

  *peType = RBU_PK_NOTABLE;
  *piPk = 0;

  assert( p->rc==SQLITE_OK );
  p->rc = prepareFreeAndCollectError(p->dbMain, &aStmt[0], &p->zErrmsg, 
    sqlite3_mprintf(
          "SELECT (sql LIKE 'create virtual%%'), rootpage"
          "  FROM sqlite_master"
          " WHERE name=%Q", zTab
  ));
  if( p->rc!=SQLITE_OK || sqlite3_step(aStmt[0])!=SQLITE_ROW ){
    /* Either an error, or no such table. */
    goto rbuTableType_end;
  }
  if( sqlite3_column_int(aStmt[0], 0) ){
    *peType = RBU_PK_VTAB;                     /* virtual table */
    goto rbuTableType_end;
  }
  *piTnum = sqlite3_column_int(aStmt[0], 1);

  p->rc = prepareFreeAndCollectError(p->dbMain, &aStmt[1], &p->zErrmsg, 
    sqlite3_mprintf("PRAGMA index_list=%Q",zTab)
  );
  if( p->rc ) goto rbuTableType_end;
  while( sqlite3_step(aStmt[1])==SQLITE_ROW ){
    const u8 *zOrig = sqlite3_column_text(aStmt[1], 3);
    const u8 *zIdx = sqlite3_column_text(aStmt[1], 1);
    if( zOrig && zIdx && zOrig[0]=='p' ){
      p->rc = prepareFreeAndCollectError(p->dbMain, &aStmt[2], &p->zErrmsg, 
          sqlite3_mprintf(
            "SELECT rootpage FROM sqlite_master WHERE name = %Q", zIdx
      ));
      if( p->rc==SQLITE_OK ){
        if( sqlite3_step(aStmt[2])==SQLITE_ROW ){
          *piPk = sqlite3_column_int(aStmt[2], 0);
          *peType = RBU_PK_EXTERNAL;
        }else{
          *peType = RBU_PK_WITHOUT_ROWID;
        }
      }
      goto rbuTableType_end;
    }
  }

  p->rc = prepareFreeAndCollectError(p->dbMain, &aStmt[3], &p->zErrmsg, 
    sqlite3_mprintf("PRAGMA table_info=%Q",zTab)
  );
  if( p->rc==SQLITE_OK ){
    while( sqlite3_step(aStmt[3])==SQLITE_ROW ){
      if( sqlite3_column_int(aStmt[3],5)>0 ){
        *peType = RBU_PK_IPK;                /* explicit IPK column */
        goto rbuTableType_end;
      }
    }
    *peType = RBU_PK_NONE;
  }

rbuTableType_end: {
    int i;
    for(i=0; i<sizeof(aStmt)/sizeof(aStmt[0]); i++){
      rbuFinalize(p, aStmt[i]);
    }
  }
}

/*
** This is a helper function for rbuObjIterCacheTableInfo(). It populates
** the pIter->abIndexed[] array.
*/
static void rbuObjIterCacheIndexedCols(sqlite3rbu *p, RbuObjIter *pIter){
  sqlite3_stmt *pList = 0;
  int bIndex = 0;

  if( p->rc==SQLITE_OK ){
    memcpy(pIter->abIndexed, pIter->abTblPk, sizeof(u8)*pIter->nTblCol);
    p->rc = prepareFreeAndCollectError(p->dbMain, &pList, &p->zErrmsg,
        sqlite3_mprintf("PRAGMA main.index_list = %Q", pIter->zTbl)
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    p->rc = prepareFreeAndCollectError(p->dbMain, &pXInfo, &p->zErrmsg,
        sqlite3_mprintf("PRAGMA main.index_xinfo = %Q", zIdx)
    );
    while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pXInfo) ){
      int iCid = sqlite3_column_int(pXInfo, 1);
      if( iCid>=0 ) pIter->abIndexed[iCid] = 1;
    }
    otaFinalize(p, pXInfo);
    bIndex = 1;
  }

  otaFinalize(p, pList);
  if( bIndex==0 ) pIter->abIndexed = 0;
}


/*
** If they are not already populated, populate the pIter->azTblCol[],
** pIter->abTblPk[], pIter->nTblCol and pIter->bRowid variables according to
** the table (not index) that the iterator currently points to.
**
** Return SQLITE_OK if successful, or an SQLite error code otherwise. If
** an error does occur, an error code and error message are also left in 
** the OTA handle.
*/
static int otaObjIterCacheTableInfo(sqlite3ota *p, OtaObjIter *pIter){
  if( pIter->azTblCol==0 ){
    sqlite3_stmt *pStmt = 0;
    int nCol = 0;
    int i;                        /* for() loop iterator variable */
    int bOtaRowid = 0;            /* If input table has column "ota_rowid" */
    int iOrder = 0;
    int iTnum = 0;

    /* Figure out the type of table this step will deal with. */
    assert( pIter->eType==0 );
    otaTableType(p, pIter->zTbl, &pIter->eType, &iTnum, &pIter->iPkTnum);
    if( p->rc==SQLITE_OK && pIter->eType==OTA_PK_NOTABLE ){
      p->rc = SQLITE_ERROR;
      p->zErrmsg = sqlite3_mprintf("no such table: %s", pIter->zTbl);
    }
    if( p->rc ) return p->rc;
    if( pIter->zIdx==0 ) pIter->iTnum = iTnum;

    assert( pIter->eType==OTA_PK_NONE || pIter->eType==OTA_PK_IPK 
         || pIter->eType==OTA_PK_EXTERNAL || pIter->eType==OTA_PK_WITHOUT_ROWID
         || pIter->eType==OTA_PK_VTAB
    );

    /* Populate the azTblCol[] and nTblCol variables based on the columns
    ** of the input table. Ignore any input table columns that begin with
    ** "ota_".  */
    p->rc = prepareFreeAndCollectError(p->dbOta, &pStmt, &p->zErrmsg, 
        sqlite3_mprintf("SELECT * FROM 'data_%q'", pIter->zTbl)
    );
    if( p->rc==SQLITE_OK ){
      nCol = sqlite3_column_count(pStmt);
      otaAllocateIterArrays(p, pIter, nCol);
    }
    for(i=0; p->rc==SQLITE_OK && i<nCol; i++){
      const char *zName = (const char*)sqlite3_column_name(pStmt, i);
      if( sqlite3_strnicmp("ota_", zName, 4) ){
        char *zCopy = otaStrndup(zName, &p->rc);
        pIter->aiSrcOrder[pIter->nTblCol] = pIter->nTblCol;
        pIter->azTblCol[pIter->nTblCol++] = zCopy;
      }
      else if( 0==sqlite3_stricmp("ota_rowid", zName) ){
        bOtaRowid = 1;
      }
    }
    sqlite3_finalize(pStmt);
    pStmt = 0;

    if( p->rc==SQLITE_OK
     && bOtaRowid!=(pIter->eType==OTA_PK_VTAB || pIter->eType==OTA_PK_NONE)
    ){
      p->rc = SQLITE_ERROR;
      p->zErrmsg = sqlite3_mprintf(
          "table data_%q %s ota_rowid column", pIter->zTbl,
          (bOtaRowid ? "may not have" : "requires")
      );
    }

    /* Check that all non-HIDDEN columns in the destination table are also
    ** present in the input table. Populate the abTblPk[], azTblType[] and
    ** aiTblOrder[] arrays at the same time.  */
    if( p->rc==SQLITE_OK ){







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    p->rc = prepareFreeAndCollectError(p->dbMain, &pXInfo, &p->zErrmsg,
        sqlite3_mprintf("PRAGMA main.index_xinfo = %Q", zIdx)
    );
    while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pXInfo) ){
      int iCid = sqlite3_column_int(pXInfo, 1);
      if( iCid>=0 ) pIter->abIndexed[iCid] = 1;
    }
    rbuFinalize(p, pXInfo);
    bIndex = 1;
  }

  rbuFinalize(p, pList);
  if( bIndex==0 ) pIter->abIndexed = 0;
}


/*
** If they are not already populated, populate the pIter->azTblCol[],
** pIter->abTblPk[], pIter->nTblCol and pIter->bRowid variables according to
** the table (not index) that the iterator currently points to.
**
** Return SQLITE_OK if successful, or an SQLite error code otherwise. If
** an error does occur, an error code and error message are also left in 
** the RBU handle.
*/
static int rbuObjIterCacheTableInfo(sqlite3rbu *p, RbuObjIter *pIter){
  if( pIter->azTblCol==0 ){
    sqlite3_stmt *pStmt = 0;
    int nCol = 0;
    int i;                        /* for() loop iterator variable */
    int bRbuRowid = 0;            /* If input table has column "rbu_rowid" */
    int iOrder = 0;
    int iTnum = 0;

    /* Figure out the type of table this step will deal with. */
    assert( pIter->eType==0 );
    rbuTableType(p, pIter->zTbl, &pIter->eType, &iTnum, &pIter->iPkTnum);
    if( p->rc==SQLITE_OK && pIter->eType==RBU_PK_NOTABLE ){
      p->rc = SQLITE_ERROR;
      p->zErrmsg = sqlite3_mprintf("no such table: %s", pIter->zTbl);
    }
    if( p->rc ) return p->rc;
    if( pIter->zIdx==0 ) pIter->iTnum = iTnum;

    assert( pIter->eType==RBU_PK_NONE || pIter->eType==RBU_PK_IPK 
         || pIter->eType==RBU_PK_EXTERNAL || pIter->eType==RBU_PK_WITHOUT_ROWID
         || pIter->eType==RBU_PK_VTAB
    );

    /* Populate the azTblCol[] and nTblCol variables based on the columns
    ** of the input table. Ignore any input table columns that begin with
    ** "rbu_".  */
    p->rc = prepareFreeAndCollectError(p->dbRbu, &pStmt, &p->zErrmsg, 
        sqlite3_mprintf("SELECT * FROM 'data_%q'", pIter->zTbl)
    );
    if( p->rc==SQLITE_OK ){
      nCol = sqlite3_column_count(pStmt);
      rbuAllocateIterArrays(p, pIter, nCol);
    }
    for(i=0; p->rc==SQLITE_OK && i<nCol; i++){
      const char *zName = (const char*)sqlite3_column_name(pStmt, i);
      if( sqlite3_strnicmp("rbu_", zName, 4) ){
        char *zCopy = rbuStrndup(zName, &p->rc);
        pIter->aiSrcOrder[pIter->nTblCol] = pIter->nTblCol;
        pIter->azTblCol[pIter->nTblCol++] = zCopy;
      }
      else if( 0==sqlite3_stricmp("rbu_rowid", zName) ){
        bRbuRowid = 1;
      }
    }
    sqlite3_finalize(pStmt);
    pStmt = 0;

    if( p->rc==SQLITE_OK
     && bRbuRowid!=(pIter->eType==RBU_PK_VTAB || pIter->eType==RBU_PK_NONE)
    ){
      p->rc = SQLITE_ERROR;
      p->zErrmsg = sqlite3_mprintf(
          "table data_%q %s rbu_rowid column", pIter->zTbl,
          (bRbuRowid ? "may not have" : "requires")
      );
    }

    /* Check that all non-HIDDEN columns in the destination table are also
    ** present in the input table. Populate the abTblPk[], azTblType[] and
    ** aiTblOrder[] arrays at the same time.  */
    if( p->rc==SQLITE_OK ){
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        const char *zType = (const char*)sqlite3_column_text(pStmt, 2);

        if( i!=iOrder ){
          SWAP(int, pIter->aiSrcOrder[i], pIter->aiSrcOrder[iOrder]);
          SWAP(char*, pIter->azTblCol[i], pIter->azTblCol[iOrder]);
        }

        pIter->azTblType[iOrder] = otaStrndup(zType, &p->rc);
        pIter->abTblPk[iOrder] = (iPk!=0);
        pIter->abNotNull[iOrder] = (u8)bNotNull || (iPk!=0);
        iOrder++;
      }
    }

    otaFinalize(p, pStmt);
    otaObjIterCacheIndexedCols(p, pIter);
    assert( pIter->eType!=OTA_PK_VTAB || pIter->abIndexed==0 );
  }

  return p->rc;
}

/*
** This function constructs and returns a pointer to a nul-terminated 
** string containing some SQL clause or list based on one or more of the 
** column names currently stored in the pIter->azTblCol[] array.
*/
static char *otaObjIterGetCollist(
  sqlite3ota *p,                  /* OTA object */
  OtaObjIter *pIter               /* Object iterator for column names */
){
  char *zList = 0;
  const char *zSep = "";
  int i;
  for(i=0; i<pIter->nTblCol; i++){
    const char *z = pIter->azTblCol[i];
    zList = otaMPrintf(p, "%z%s\"%w\"", zList, zSep, z);
    zSep = ", ";
  }
  return zList;
}

/*
** This function is used to create a SELECT list (the list of SQL 
** expressions that follows a SELECT keyword) for a SELECT statement 
** used to read from an data_xxx or ota_tmp_xxx table while updating the 
** index object currently indicated by the iterator object passed as the 
** second argument. A "PRAGMA index_xinfo = <idxname>" statement is used 
** to obtain the required information.
**
** If the index is of the following form:
**
**   CREATE INDEX i1 ON t1(c, b COLLATE nocase);
**
** and "t1" is a table with an explicit INTEGER PRIMARY KEY column 
** "ipk", the returned string is:
**
**   "`c` COLLATE 'BINARY', `b` COLLATE 'NOCASE', `ipk` COLLATE 'BINARY'"
**
** As well as the returned string, three other malloc'd strings are 
** returned via output parameters. As follows:
**
**   pzImposterCols: ...
**   pzImposterPk: ...
**   pzWhere: ...
*/
static char *otaObjIterGetIndexCols(
  sqlite3ota *p,                  /* OTA object */
  OtaObjIter *pIter,              /* Object iterator for column names */
  char **pzImposterCols,          /* OUT: Columns for imposter table */
  char **pzImposterPk,            /* OUT: Imposter PK clause */
  char **pzWhere,                 /* OUT: WHERE clause */
  int *pnBind                     /* OUT: Total number of columns */
){
  int rc = p->rc;                 /* Error code */
  int rc2;                        /* sqlite3_finalize() return code */
  char *zRet = 0;                 /* String to return */
  char *zImpCols = 0;             /* String to return via *pzImposterCols */
  char *zImpPK = 0;               /* String to return via *pzImposterPK */
  char *zWhere = 0;               /* String to return via *pzWhere */







|






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|
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|







158231
158232
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158260
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158264
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158273
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158293
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158296
158297
158298
158299
158300
158301
158302
158303
158304
158305
158306
158307
158308
158309
158310
        const char *zType = (const char*)sqlite3_column_text(pStmt, 2);

        if( i!=iOrder ){
          SWAP(int, pIter->aiSrcOrder[i], pIter->aiSrcOrder[iOrder]);
          SWAP(char*, pIter->azTblCol[i], pIter->azTblCol[iOrder]);
        }

        pIter->azTblType[iOrder] = rbuStrndup(zType, &p->rc);
        pIter->abTblPk[iOrder] = (iPk!=0);
        pIter->abNotNull[iOrder] = (u8)bNotNull || (iPk!=0);
        iOrder++;
      }
    }

    rbuFinalize(p, pStmt);
    rbuObjIterCacheIndexedCols(p, pIter);
    assert( pIter->eType!=RBU_PK_VTAB || pIter->abIndexed==0 );
  }

  return p->rc;
}

/*
** This function constructs and returns a pointer to a nul-terminated 
** string containing some SQL clause or list based on one or more of the 
** column names currently stored in the pIter->azTblCol[] array.
*/
static char *rbuObjIterGetCollist(
  sqlite3rbu *p,                  /* RBU object */
  RbuObjIter *pIter               /* Object iterator for column names */
){
  char *zList = 0;
  const char *zSep = "";
  int i;
  for(i=0; i<pIter->nTblCol; i++){
    const char *z = pIter->azTblCol[i];
    zList = rbuMPrintf(p, "%z%s\"%w\"", zList, zSep, z);
    zSep = ", ";
  }
  return zList;
}

/*
** This function is used to create a SELECT list (the list of SQL 
** expressions that follows a SELECT keyword) for a SELECT statement 
** used to read from an data_xxx or rbu_tmp_xxx table while updating the 
** index object currently indicated by the iterator object passed as the 
** second argument. A "PRAGMA index_xinfo = <idxname>" statement is used 
** to obtain the required information.
**
** If the index is of the following form:
**
**   CREATE INDEX i1 ON t1(c, b COLLATE nocase);
**
** and "t1" is a table with an explicit INTEGER PRIMARY KEY column 
** "ipk", the returned string is:
**
**   "`c` COLLATE 'BINARY', `b` COLLATE 'NOCASE', `ipk` COLLATE 'BINARY'"
**
** As well as the returned string, three other malloc'd strings are 
** returned via output parameters. As follows:
**
**   pzImposterCols: ...
**   pzImposterPk: ...
**   pzWhere: ...
*/
static char *rbuObjIterGetIndexCols(
  sqlite3rbu *p,                  /* RBU object */
  RbuObjIter *pIter,              /* Object iterator for column names */
  char **pzImposterCols,          /* OUT: Columns for imposter table */
  char **pzImposterPk,            /* OUT: Imposter PK clause */
  char **pzWhere,                 /* OUT: WHERE clause */
  int *pnBind                     /* OUT: Trbul number of columns */
){
  int rc = p->rc;                 /* Error code */
  int rc2;                        /* sqlite3_finalize() return code */
  char *zRet = 0;                 /* String to return */
  char *zImpCols = 0;             /* String to return via *pzImposterCols */
  char *zImpPK = 0;               /* String to return via *pzImposterPK */
  char *zWhere = 0;               /* String to return via *pzWhere */
158319
158320
158321
158322
158323
158324
158325
158326
158327
158328
158329
158330
158331
158332
158333
158334
158335
158336
158337
158338
158339
158340
158341
158342
158343
158344
158345
158346
158347
158348
158349
158350
158351
158352
158353
158354
158355
158356
158357
158358
158359
    int bDesc = sqlite3_column_int(pXInfo, 3);
    const char *zCollate = (const char*)sqlite3_column_text(pXInfo, 4);
    const char *zCol;
    const char *zType;

    if( iCid<0 ){
      /* An integer primary key. If the table has an explicit IPK, use
      ** its name. Otherwise, use "ota_rowid".  */
      if( pIter->eType==OTA_PK_IPK ){
        int i;
        for(i=0; pIter->abTblPk[i]==0; i++);
        assert( i<pIter->nTblCol );
        zCol = pIter->azTblCol[i];
      }else{
        zCol = "ota_rowid";
      }
      zType = "INTEGER";
    }else{
      zCol = pIter->azTblCol[iCid];
      zType = pIter->azTblType[iCid];
    }

    zRet = sqlite3_mprintf("%z%s\"%w\" COLLATE %Q", zRet, zCom, zCol, zCollate);
    if( pIter->bUnique==0 || sqlite3_column_int(pXInfo, 5) ){
      const char *zOrder = (bDesc ? " DESC" : "");
      zImpPK = sqlite3_mprintf("%z%s\"ota_imp_%d%w\"%s", 
          zImpPK, zCom, nBind, zCol, zOrder
      );
    }
    zImpCols = sqlite3_mprintf("%z%s\"ota_imp_%d%w\" %s COLLATE %Q", 
        zImpCols, zCom, nBind, zCol, zType, zCollate
    );
    zWhere = sqlite3_mprintf(
        "%z%s\"ota_imp_%d%w\" IS ?", zWhere, zAnd, nBind, zCol
    );
    if( zRet==0 || zImpPK==0 || zImpCols==0 || zWhere==0 ) rc = SQLITE_NOMEM;
    zCom = ", ";
    zAnd = " AND ";
    nBind++;
  }








|
|





|










|



|



|







158325
158326
158327
158328
158329
158330
158331
158332
158333
158334
158335
158336
158337
158338
158339
158340
158341
158342
158343
158344
158345
158346
158347
158348
158349
158350
158351
158352
158353
158354
158355
158356
158357
158358
158359
158360
158361
158362
158363
158364
158365
    int bDesc = sqlite3_column_int(pXInfo, 3);
    const char *zCollate = (const char*)sqlite3_column_text(pXInfo, 4);
    const char *zCol;
    const char *zType;

    if( iCid<0 ){
      /* An integer primary key. If the table has an explicit IPK, use
      ** its name. Otherwise, use "rbu_rowid".  */
      if( pIter->eType==RBU_PK_IPK ){
        int i;
        for(i=0; pIter->abTblPk[i]==0; i++);
        assert( i<pIter->nTblCol );
        zCol = pIter->azTblCol[i];
      }else{
        zCol = "rbu_rowid";
      }
      zType = "INTEGER";
    }else{
      zCol = pIter->azTblCol[iCid];
      zType = pIter->azTblType[iCid];
    }

    zRet = sqlite3_mprintf("%z%s\"%w\" COLLATE %Q", zRet, zCom, zCol, zCollate);
    if( pIter->bUnique==0 || sqlite3_column_int(pXInfo, 5) ){
      const char *zOrder = (bDesc ? " DESC" : "");
      zImpPK = sqlite3_mprintf("%z%s\"rbu_imp_%d%w\"%s", 
          zImpPK, zCom, nBind, zCol, zOrder
      );
    }
    zImpCols = sqlite3_mprintf("%z%s\"rbu_imp_%d%w\" %s COLLATE %Q", 
        zImpCols, zCom, nBind, zCol, zType, zCollate
    );
    zWhere = sqlite3_mprintf(
        "%z%s\"rbu_imp_%d%w\" IS ?", zWhere, zAnd, nBind, zCol
    );
    if( zRet==0 || zImpPK==0 || zImpCols==0 || zWhere==0 ) rc = SQLITE_NOMEM;
    zCom = ", ";
    zAnd = " AND ";
    nBind++;
  }

158383
158384
158385
158386
158387
158388
158389
158390
158391
158392
158393
158394
158395
158396
158397
158398
158399
158400
158401
158402
** Assuming the current table columns are "a", "b" and "c", and the zObj
** paramter is passed "old", return a string of the form:
**
**     "old.a, old.b, old.b"
**
** With the column names escaped.
**
** For tables with implicit rowids - OTA_PK_EXTERNAL and OTA_PK_NONE, append
** the text ", old._rowid_" to the returned value.
*/
static char *otaObjIterGetOldlist(
  sqlite3ota *p, 
  OtaObjIter *pIter,
  const char *zObj
){
  char *zList = 0;
  if( p->rc==SQLITE_OK && pIter->abIndexed ){
    const char *zS = "";
    int i;
    for(i=0; i<pIter->nTblCol; i++){







|


|
|
|







158389
158390
158391
158392
158393
158394
158395
158396
158397
158398
158399
158400
158401
158402
158403
158404
158405
158406
158407
158408
** Assuming the current table columns are "a", "b" and "c", and the zObj
** paramter is passed "old", return a string of the form:
**
**     "old.a, old.b, old.b"
**
** With the column names escaped.
**
** For tables with implicit rowids - RBU_PK_EXTERNAL and RBU_PK_NONE, append
** the text ", old._rowid_" to the returned value.
*/
static char *rbuObjIterGetOldlist(
  sqlite3rbu *p, 
  RbuObjIter *pIter,
  const char *zObj
){
  char *zList = 0;
  if( p->rc==SQLITE_OK && pIter->abIndexed ){
    const char *zS = "";
    int i;
    for(i=0; i<pIter->nTblCol; i++){
158410
158411
158412
158413
158414
158415
158416
158417
158418
158419
158420
158421
158422
158423
158424
158425
158426
158427
158428
158429
158430
158431
158432
158433
158434
158435
158436
158437
158438
158439
158440
158441
158442
158443
158444
158445
158446
158447
158448
158449
158450
158451
158452
158453
158454
158455
158456
158457
158458
158459
158460
158461
158462
158463
158464
158465
158466
158467
158468
158469
158470
158471
158472
158473
158474
158475
158476
158477
158478
158479
158480
158481
158482
158483
158484
158485
158486
158487
158488
158489
158490
158491
158492
158493
158494
158495
158496
158497
158498
158499
158500
158501
158502
158503
158504
158505
158506
158507
158508
158509
158510
158511
158512
158513
158514
158515
158516
158517
158518
158519
158520
158521
158522
158523
158524
158525
158526
158527
158528
158529
158530
158531
158532
158533
158534
158535
158536
158537
158538
158539
158540
158541
158542
158543
158544
158545
158546
158547
158548
158549
158550
158551
158552
158553
158554
158555
158556
158557
158558
158559
158560
158561
158562
158563
158564
158565
158566
158567
158568
158569
158570
158571
158572
158573
158574
158575
158576
158577
158578
158579
158580
      if( zList==0 ){
        p->rc = SQLITE_NOMEM;
        break;
      }
    }

    /* For a table with implicit rowids, append "old._rowid_" to the list. */
    if( pIter->eType==OTA_PK_EXTERNAL || pIter->eType==OTA_PK_NONE ){
      zList = otaMPrintf(p, "%z, %s._rowid_", zList, zObj);
    }
  }
  return zList;
}

/*
** Return an expression that can be used in a WHERE clause to match the
** primary key of the current table. For example, if the table is:
**
**   CREATE TABLE t1(a, b, c, PRIMARY KEY(b, c));
**
** Return the string:
**
**   "b = ?1 AND c = ?2"
*/
static char *otaObjIterGetWhere(
  sqlite3ota *p, 
  OtaObjIter *pIter
){
  char *zList = 0;
  if( pIter->eType==OTA_PK_VTAB || pIter->eType==OTA_PK_NONE ){
    zList = otaMPrintf(p, "_rowid_ = ?%d", pIter->nTblCol+1);
  }else if( pIter->eType==OTA_PK_EXTERNAL ){
    const char *zSep = "";
    int i;
    for(i=0; i<pIter->nTblCol; i++){
      if( pIter->abTblPk[i] ){
        zList = otaMPrintf(p, "%z%sc%d=?%d", zList, zSep, i, i+1);
        zSep = " AND ";
      }
    }
    zList = otaMPrintf(p, 
        "_rowid_ = (SELECT id FROM ota_imposter2 WHERE %z)", zList
    );

  }else{
    const char *zSep = "";
    int i;
    for(i=0; i<pIter->nTblCol; i++){
      if( pIter->abTblPk[i] ){
        const char *zCol = pIter->azTblCol[i];
        zList = otaMPrintf(p, "%z%s\"%w\"=?%d", zList, zSep, zCol, i+1);
        zSep = " AND ";
      }
    }
  }
  return zList;
}

/*
** The SELECT statement iterating through the keys for the current object
** (p->objiter.pSelect) currently points to a valid row. However, there
** is something wrong with the ota_control value in the ota_control value
** stored in the (p->nCol+1)'th column. Set the error code and error message
** of the OTA handle to something reflecting this.
*/
static void otaBadControlError(sqlite3ota *p){
  p->rc = SQLITE_ERROR;
  p->zErrmsg = sqlite3_mprintf("invalid ota_control value");
}


/*
** Return a nul-terminated string containing the comma separated list of
** assignments that should be included following the "SET" keyword of
** an UPDATE statement used to update the table object that the iterator
** passed as the second argument currently points to if the ota_control
** column of the data_xxx table entry is set to zMask.
**
** The memory for the returned string is obtained from sqlite3_malloc().
** It is the responsibility of the caller to eventually free it using
** sqlite3_free(). 
**
** If an OOM error is encountered when allocating space for the new
** string, an error code is left in the ota handle passed as the first
** argument and NULL is returned. Or, if an error has already occurred
** when this function is called, NULL is returned immediately, without
** attempting the allocation or modifying the stored error code.
*/
static char *otaObjIterGetSetlist(
  sqlite3ota *p,
  OtaObjIter *pIter,
  const char *zMask
){
  char *zList = 0;
  if( p->rc==SQLITE_OK ){
    int i;

    if( strlen(zMask)!=pIter->nTblCol ){
      otaBadControlError(p);
    }else{
      const char *zSep = "";
      for(i=0; i<pIter->nTblCol; i++){
        char c = zMask[pIter->aiSrcOrder[i]];
        if( c=='x' ){
          zList = otaMPrintf(p, "%z%s\"%w\"=?%d", 
              zList, zSep, pIter->azTblCol[i], i+1
          );
          zSep = ", ";
        }
        if( c=='d' ){
          zList = otaMPrintf(p, "%z%s\"%w\"=ota_delta(\"%w\", ?%d)", 
              zList, zSep, pIter->azTblCol[i], pIter->azTblCol[i], i+1
          );
          zSep = ", ";
        }
      }
    }
  }
  return zList;
}

/*
** Return a nul-terminated string consisting of nByte comma separated
** "?" expressions. For example, if nByte is 3, return a pointer to
** a buffer containing the string "?,?,?".
**
** The memory for the returned string is obtained from sqlite3_malloc().
** It is the responsibility of the caller to eventually free it using
** sqlite3_free(). 
**
** If an OOM error is encountered when allocating space for the new
** string, an error code is left in the ota handle passed as the first
** argument and NULL is returned. Or, if an error has already occurred
** when this function is called, NULL is returned immediately, without
** attempting the allocation or modifying the stored error code.
*/
static char *otaObjIterGetBindlist(sqlite3ota *p, int nBind){
  char *zRet = 0;
  int nByte = nBind*2 + 1;

  zRet = (char*)otaMalloc(p, nByte);
  if( zRet ){
    int i;
    for(i=0; i<nBind; i++){
      zRet[i*2] = '?';
      zRet[i*2+1] = (i+1==nBind) ? '\0' : ',';
    }
  }
  return zRet;
}

/*
** The iterator currently points to a table (not index) of type 
** OTA_PK_WITHOUT_ROWID. This function creates the PRIMARY KEY 
** declaration for the corresponding imposter table. For example,
** if the iterator points to a table created as:
**
**   CREATE TABLE t1(a, b, c, PRIMARY KEY(b, a DESC)) WITHOUT ROWID
**
** this function returns:
**
**   PRIMARY KEY("b", "a" DESC)
*/
static char *otaWithoutRowidPK(sqlite3ota *p, OtaObjIter *pIter){
  char *z = 0;
  assert( pIter->zIdx==0 );
  if( p->rc==SQLITE_OK ){
    const char *zSep = "PRIMARY KEY(";
    sqlite3_stmt *pXList = 0;     /* PRAGMA index_list = (pIter->zTbl) */
    sqlite3_stmt *pXInfo = 0;     /* PRAGMA index_xinfo = <pk-index> */
   







|
|















|
|
|


|
|
|




|



|
|








|










|

|

|

|







|







|




|
|
|







|





|





|




















|




|



|












|









|







158416
158417
158418
158419
158420
158421
158422
158423
158424
158425
158426
158427
158428
158429
158430
158431
158432
158433
158434
158435
158436
158437
158438
158439
158440
158441
158442
158443
158444
158445
158446
158447
158448
158449
158450
158451
158452
158453
158454
158455
158456
158457
158458
158459
158460
158461
158462
158463
158464
158465
158466
158467
158468
158469
158470
158471
158472
158473
158474
158475
158476
158477
158478
158479
158480
158481
158482
158483
158484
158485
158486
158487
158488
158489
158490
158491
158492
158493
158494
158495
158496
158497
158498
158499
158500
158501
158502
158503
158504
158505
158506
158507
158508
158509
158510
158511
158512
158513
158514
158515
158516
158517
158518
158519
158520
158521
158522
158523
158524
158525
158526
158527
158528
158529
158530
158531
158532
158533
158534
158535
158536
158537
158538
158539
158540
158541
158542
158543
158544
158545
158546
158547
158548
158549
158550
158551
158552
158553
158554
158555
158556
158557
158558
158559
158560
158561
158562
158563
158564
158565
158566
158567
158568
158569
158570
158571
158572
158573
158574
158575
158576
158577
158578
158579
158580
158581
158582
158583
158584
158585
158586
      if( zList==0 ){
        p->rc = SQLITE_NOMEM;
        break;
      }
    }

    /* For a table with implicit rowids, append "old._rowid_" to the list. */
    if( pIter->eType==RBU_PK_EXTERNAL || pIter->eType==RBU_PK_NONE ){
      zList = rbuMPrintf(p, "%z, %s._rowid_", zList, zObj);
    }
  }
  return zList;
}

/*
** Return an expression that can be used in a WHERE clause to match the
** primary key of the current table. For example, if the table is:
**
**   CREATE TABLE t1(a, b, c, PRIMARY KEY(b, c));
**
** Return the string:
**
**   "b = ?1 AND c = ?2"
*/
static char *rbuObjIterGetWhere(
  sqlite3rbu *p, 
  RbuObjIter *pIter
){
  char *zList = 0;
  if( pIter->eType==RBU_PK_VTAB || pIter->eType==RBU_PK_NONE ){
    zList = rbuMPrintf(p, "_rowid_ = ?%d", pIter->nTblCol+1);
  }else if( pIter->eType==RBU_PK_EXTERNAL ){
    const char *zSep = "";
    int i;
    for(i=0; i<pIter->nTblCol; i++){
      if( pIter->abTblPk[i] ){
        zList = rbuMPrintf(p, "%z%sc%d=?%d", zList, zSep, i, i+1);
        zSep = " AND ";
      }
    }
    zList = rbuMPrintf(p, 
        "_rowid_ = (SELECT id FROM rbu_imposter2 WHERE %z)", zList
    );

  }else{
    const char *zSep = "";
    int i;
    for(i=0; i<pIter->nTblCol; i++){
      if( pIter->abTblPk[i] ){
        const char *zCol = pIter->azTblCol[i];
        zList = rbuMPrintf(p, "%z%s\"%w\"=?%d", zList, zSep, zCol, i+1);
        zSep = " AND ";
      }
    }
  }
  return zList;
}

/*
** The SELECT statement iterating through the keys for the current object
** (p->objiter.pSelect) currently points to a valid row. However, there
** is something wrong with the rbu_control value in the rbu_control value
** stored in the (p->nCol+1)'th column. Set the error code and error message
** of the RBU handle to something reflecting this.
*/
static void rbuBadControlError(sqlite3rbu *p){
  p->rc = SQLITE_ERROR;
  p->zErrmsg = sqlite3_mprintf("invalid rbu_control value");
}


/*
** Return a nul-terminated string containing the comma separated list of
** assignments that should be included following the "SET" keyword of
** an UPDATE statement used to update the table object that the iterator
** passed as the second argument currently points to if the rbu_control
** column of the data_xxx table entry is set to zMask.
**
** The memory for the returned string is obtained from sqlite3_malloc().
** It is the responsibility of the caller to eventually free it using
** sqlite3_free(). 
**
** If an OOM error is encountered when allocating space for the new
** string, an error code is left in the rbu handle passed as the first
** argument and NULL is returned. Or, if an error has already occurred
** when this function is called, NULL is returned immediately, without
** attempting the allocation or modifying the stored error code.
*/
static char *rbuObjIterGetSetlist(
  sqlite3rbu *p,
  RbuObjIter *pIter,
  const char *zMask
){
  char *zList = 0;
  if( p->rc==SQLITE_OK ){
    int i;

    if( strlen(zMask)!=pIter->nTblCol ){
      rbuBadControlError(p);
    }else{
      const char *zSep = "";
      for(i=0; i<pIter->nTblCol; i++){
        char c = zMask[pIter->aiSrcOrder[i]];
        if( c=='x' ){
          zList = rbuMPrintf(p, "%z%s\"%w\"=?%d", 
              zList, zSep, pIter->azTblCol[i], i+1
          );
          zSep = ", ";
        }
        if( c=='d' ){
          zList = rbuMPrintf(p, "%z%s\"%w\"=rbu_delta(\"%w\", ?%d)", 
              zList, zSep, pIter->azTblCol[i], pIter->azTblCol[i], i+1
          );
          zSep = ", ";
        }
      }
    }
  }
  return zList;
}

/*
** Return a nul-terminated string consisting of nByte comma separated
** "?" expressions. For example, if nByte is 3, return a pointer to
** a buffer containing the string "?,?,?".
**
** The memory for the returned string is obtained from sqlite3_malloc().
** It is the responsibility of the caller to eventually free it using
** sqlite3_free(). 
**
** If an OOM error is encountered when allocating space for the new
** string, an error code is left in the rbu handle passed as the first
** argument and NULL is returned. Or, if an error has already occurred
** when this function is called, NULL is returned immediately, without
** attempting the allocation or modifying the stored error code.
*/
static char *rbuObjIterGetBindlist(sqlite3rbu *p, int nBind){
  char *zRet = 0;
  int nByte = nBind*2 + 1;

  zRet = (char*)rbuMalloc(p, nByte);
  if( zRet ){
    int i;
    for(i=0; i<nBind; i++){
      zRet[i*2] = '?';
      zRet[i*2+1] = (i+1==nBind) ? '\0' : ',';
    }
  }
  return zRet;
}

/*
** The iterator currently points to a table (not index) of type 
** RBU_PK_WITHOUT_ROWID. This function creates the PRIMARY KEY 
** declaration for the corresponding imposter table. For example,
** if the iterator points to a table created as:
**
**   CREATE TABLE t1(a, b, c, PRIMARY KEY(b, a DESC)) WITHOUT ROWID
**
** this function returns:
**
**   PRIMARY KEY("b", "a" DESC)
*/
static char *rbuWithoutRowidPK(sqlite3rbu *p, RbuObjIter *pIter){
  char *z = 0;
  assert( pIter->zIdx==0 );
  if( p->rc==SQLITE_OK ){
    const char *zSep = "PRIMARY KEY(";
    sqlite3_stmt *pXList = 0;     /* PRAGMA index_list = (pIter->zTbl) */
    sqlite3_stmt *pXInfo = 0;     /* PRAGMA index_xinfo = <pk-index> */
   
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          p->rc = prepareFreeAndCollectError(p->dbMain, &pXInfo, &p->zErrmsg,
              sqlite3_mprintf("PRAGMA main.index_xinfo = %Q", zIdx)
          );
        }
        break;
      }
    }
    otaFinalize(p, pXList);

    while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pXInfo) ){
      if( sqlite3_column_int(pXInfo, 5) ){
        /* int iCid = sqlite3_column_int(pXInfo, 0); */
        const char *zCol = (const char*)sqlite3_column_text(pXInfo, 2);
        const char *zDesc = sqlite3_column_int(pXInfo, 3) ? " DESC" : "";
        z = otaMPrintf(p, "%z%s\"%w\"%s", z, zSep, zCol, zDesc);
        zSep = ", ";
      }
    }
    z = otaMPrintf(p, "%z)", z);
    otaFinalize(p, pXInfo);
  }
  return z;
}

/*
** This function creates the second imposter table used when writing to
** a table b-tree where the table has an external primary key. If the
** iterator passed as the second argument does not currently point to
** a table (not index) with an external primary key, this function is a
** no-op. 
**
** Assuming the iterator does point to a table with an external PK, this
** function creates a WITHOUT ROWID imposter table named "ota_imposter2"
** used to access that PK index. For example, if the target table is
** declared as follows:
**
**   CREATE TABLE t1(a, b TEXT, c REAL, PRIMARY KEY(b, c));
**
** then the imposter table schema is:
**
**   CREATE TABLE ota_imposter2(c1 TEXT, c2 REAL, id INTEGER) WITHOUT ROWID;
**
*/
static void otaCreateImposterTable2(sqlite3ota *p, OtaObjIter *pIter){
  if( p->rc==SQLITE_OK && pIter->eType==OTA_PK_EXTERNAL ){
    int tnum = pIter->iPkTnum;    /* Root page of PK index */
    sqlite3_stmt *pQuery = 0;     /* SELECT name ... WHERE rootpage = $tnum */
    const char *zIdx = 0;         /* Name of PK index */
    sqlite3_stmt *pXInfo = 0;     /* PRAGMA main.index_xinfo = $zIdx */
    const char *zComma = "";
    char *zCols = 0;              /* Used to build up list of table cols */
    char *zPk = 0;                /* Used to build up table PK declaration */







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          p->rc = prepareFreeAndCollectError(p->dbMain, &pXInfo, &p->zErrmsg,
              sqlite3_mprintf("PRAGMA main.index_xinfo = %Q", zIdx)
          );
        }
        break;
      }
    }
    rbuFinalize(p, pXList);

    while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pXInfo) ){
      if( sqlite3_column_int(pXInfo, 5) ){
        /* int iCid = sqlite3_column_int(pXInfo, 0); */
        const char *zCol = (const char*)sqlite3_column_text(pXInfo, 2);
        const char *zDesc = sqlite3_column_int(pXInfo, 3) ? " DESC" : "";
        z = rbuMPrintf(p, "%z%s\"%w\"%s", z, zSep, zCol, zDesc);
        zSep = ", ";
      }
    }
    z = rbuMPrintf(p, "%z)", z);
    rbuFinalize(p, pXInfo);
  }
  return z;
}

/*
** This function creates the second imposter table used when writing to
** a table b-tree where the table has an external primary key. If the
** iterator passed as the second argument does not currently point to
** a table (not index) with an external primary key, this function is a
** no-op. 
**
** Assuming the iterator does point to a table with an external PK, this
** function creates a WITHOUT ROWID imposter table named "rbu_imposter2"
** used to access that PK index. For example, if the target table is
** declared as follows:
**
**   CREATE TABLE t1(a, b TEXT, c REAL, PRIMARY KEY(b, c));
**
** then the imposter table schema is:
**
**   CREATE TABLE rbu_imposter2(c1 TEXT, c2 REAL, id INTEGER) WITHOUT ROWID;
**
*/
static void rbuCreateImposterTable2(sqlite3rbu *p, RbuObjIter *pIter){
  if( p->rc==SQLITE_OK && pIter->eType==RBU_PK_EXTERNAL ){
    int tnum = pIter->iPkTnum;    /* Root page of PK index */
    sqlite3_stmt *pQuery = 0;     /* SELECT name ... WHERE rootpage = $tnum */
    const char *zIdx = 0;         /* Name of PK index */
    sqlite3_stmt *pXInfo = 0;     /* PRAGMA main.index_xinfo = $zIdx */
    const char *zComma = "";
    char *zCols = 0;              /* Used to build up list of table cols */
    char *zPk = 0;                /* Used to build up table PK declaration */
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      }
    }
    if( zIdx ){
      p->rc = prepareFreeAndCollectError(p->dbMain, &pXInfo, &p->zErrmsg,
          sqlite3_mprintf("PRAGMA main.index_xinfo = %Q", zIdx)
      );
    }
    otaFinalize(p, pQuery);

    while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pXInfo) ){
      int bKey = sqlite3_column_int(pXInfo, 5);
      if( bKey ){
        int iCid = sqlite3_column_int(pXInfo, 1);
        int bDesc = sqlite3_column_int(pXInfo, 3);
        const char *zCollate = (const char*)sqlite3_column_text(pXInfo, 4);
        zCols = otaMPrintf(p, "%z%sc%d %s COLLATE %s", zCols, zComma, 
            iCid, pIter->azTblType[iCid], zCollate
        );
        zPk = otaMPrintf(p, "%z%sc%d%s", zPk, zComma, iCid, bDesc?" DESC":"");
        zComma = ", ";
      }
    }
    zCols = otaMPrintf(p, "%z, id INTEGER", zCols);
    otaFinalize(p, pXInfo);

    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 1, tnum);
    otaMPrintfExec(p, p->dbMain,
        "CREATE TABLE ota_imposter2(%z, PRIMARY KEY(%z)) WITHOUT ROWID", 
        zCols, zPk
    );
    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 0);
  }
}

/*
** If an error has already occurred when this function is called, it 
** immediately returns zero (without doing any work). Or, if an error
** occurs during the execution of this function, it sets the error code
** in the sqlite3ota object indicated by the first argument and returns
** zero.
**
** The iterator passed as the second argument is guaranteed to point to
** a table (not an index) when this function is called. This function
** attempts to create any imposter table required to write to the main
** table b-tree of the table before returning. Non-zero is returned if
** an imposter table are created, or zero otherwise.
**
** An imposter table is required in all cases except OTA_PK_VTAB. Only
** virtual tables are written to directly. The imposter table has the 
** same schema as the actual target table (less any UNIQUE constraints). 
** More precisely, the "same schema" means the same columns, types, 
** collation sequences. For tables that do not have an external PRIMARY
** KEY, it also means the same PRIMARY KEY declaration.
*/
static void otaCreateImposterTable(sqlite3ota *p, OtaObjIter *pIter){
  if( p->rc==SQLITE_OK && pIter->eType!=OTA_PK_VTAB ){
    int tnum = pIter->iTnum;
    const char *zComma = "";
    char *zSql = 0;
    int iCol;
    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 1);

    for(iCol=0; p->rc==SQLITE_OK && iCol<pIter->nTblCol; iCol++){
      const char *zPk = "";
      const char *zCol = pIter->azTblCol[iCol];
      const char *zColl = 0;

      p->rc = sqlite3_table_column_metadata(
          p->dbMain, "main", pIter->zTbl, zCol, 0, &zColl, 0, 0, 0
      );

      if( pIter->eType==OTA_PK_IPK && pIter->abTblPk[iCol] ){
        /* If the target table column is an "INTEGER PRIMARY KEY", add
        ** "PRIMARY KEY" to the imposter table column declaration. */
        zPk = "PRIMARY KEY ";
      }
      zSql = otaMPrintf(p, "%z%s\"%w\" %s %sCOLLATE %s%s", 
          zSql, zComma, zCol, pIter->azTblType[iCol], zPk, zColl,
          (pIter->abNotNull[iCol] ? " NOT NULL" : "")
      );
      zComma = ", ";
    }

    if( pIter->eType==OTA_PK_WITHOUT_ROWID ){
      char *zPk = otaWithoutRowidPK(p, pIter);
      if( zPk ){
        zSql = otaMPrintf(p, "%z, %z", zSql, zPk);
      }
    }

    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 1, tnum);
    otaMPrintfExec(p, p->dbMain, "CREATE TABLE \"ota_imp_%w\"(%z)%s", 
        pIter->zTbl, zSql, 
        (pIter->eType==OTA_PK_WITHOUT_ROWID ? " WITHOUT ROWID" : "")
    );
    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 0);
  }
}

/*
** Prepare a statement used to insert rows into the "ota_tmp_xxx" table.
** Specifically a statement of the form:
**
**     INSERT INTO ota_tmp_xxx VALUES(?, ?, ? ...);
**
** The number of bound variables is equal to the number of columns in
** the target table, plus one (for the ota_control column), plus one more 
** (for the ota_rowid column) if the target table is an implicit IPK or 
** virtual table.
*/
static void otaObjIterPrepareTmpInsert(
  sqlite3ota *p, 
  OtaObjIter *pIter,
  const char *zCollist,
  const char *zOtaRowid
){
  int bOtaRowid = (pIter->eType==OTA_PK_EXTERNAL || pIter->eType==OTA_PK_NONE);
  char *zBind = otaObjIterGetBindlist(p, pIter->nTblCol + 1 + bOtaRowid);
  if( zBind ){
    assert( pIter->pTmpInsert==0 );
    p->rc = prepareFreeAndCollectError(
        p->dbOta, &pIter->pTmpInsert, &p->zErrmsg, sqlite3_mprintf(
          "INSERT INTO %s.'ota_tmp_%q'(ota_control,%s%s) VALUES(%z)", 
          p->zStateDb, pIter->zTbl, zCollist, zOtaRowid, zBind
    ));
  }
}

static void otaTmpInsertFunc(
  sqlite3_context *pCtx, 
  int nVal,
  sqlite3_value **apVal
){
  sqlite3ota *p = sqlite3_user_data(pCtx);
  int rc = SQLITE_OK;
  int i;

  for(i=0; rc==SQLITE_OK && i<nVal; i++){
    rc = sqlite3_bind_value(p->objiter.pTmpInsert, i+1, apVal[i]);
  }
  if( rc==SQLITE_OK ){







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      }
    }
    if( zIdx ){
      p->rc = prepareFreeAndCollectError(p->dbMain, &pXInfo, &p->zErrmsg,
          sqlite3_mprintf("PRAGMA main.index_xinfo = %Q", zIdx)
      );
    }
    rbuFinalize(p, pQuery);

    while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pXInfo) ){
      int bKey = sqlite3_column_int(pXInfo, 5);
      if( bKey ){
        int iCid = sqlite3_column_int(pXInfo, 1);
        int bDesc = sqlite3_column_int(pXInfo, 3);
        const char *zCollate = (const char*)sqlite3_column_text(pXInfo, 4);
        zCols = rbuMPrintf(p, "%z%sc%d %s COLLATE %s", zCols, zComma, 
            iCid, pIter->azTblType[iCid], zCollate
        );
        zPk = rbuMPrintf(p, "%z%sc%d%s", zPk, zComma, iCid, bDesc?" DESC":"");
        zComma = ", ";
      }
    }
    zCols = rbuMPrintf(p, "%z, id INTEGER", zCols);
    rbuFinalize(p, pXInfo);

    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 1, tnum);
    rbuMPrintfExec(p, p->dbMain,
        "CREATE TABLE rbu_imposter2(%z, PRIMARY KEY(%z)) WITHOUT ROWID", 
        zCols, zPk
    );
    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 0);
  }
}

/*
** If an error has already occurred when this function is called, it 
** immediately returns zero (without doing any work). Or, if an error
** occurs during the execution of this function, it sets the error code
** in the sqlite3rbu object indicated by the first argument and returns
** zero.
**
** The iterator passed as the second argument is guaranteed to point to
** a table (not an index) when this function is called. This function
** attempts to create any imposter table required to write to the main
** table b-tree of the table before returning. Non-zero is returned if
** an imposter table are created, or zero otherwise.
**
** An imposter table is required in all cases except RBU_PK_VTAB. Only
** virtual tables are written to directly. The imposter table has the 
** same schema as the actual target table (less any UNIQUE constraints). 
** More precisely, the "same schema" means the same columns, types, 
** collation sequences. For tables that do not have an external PRIMARY
** KEY, it also means the same PRIMARY KEY declaration.
*/
static void rbuCreateImposterTable(sqlite3rbu *p, RbuObjIter *pIter){
  if( p->rc==SQLITE_OK && pIter->eType!=RBU_PK_VTAB ){
    int tnum = pIter->iTnum;
    const char *zComma = "";
    char *zSql = 0;
    int iCol;
    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 1);

    for(iCol=0; p->rc==SQLITE_OK && iCol<pIter->nTblCol; iCol++){
      const char *zPk = "";
      const char *zCol = pIter->azTblCol[iCol];
      const char *zColl = 0;

      p->rc = sqlite3_table_column_metadata(
          p->dbMain, "main", pIter->zTbl, zCol, 0, &zColl, 0, 0, 0
      );

      if( pIter->eType==RBU_PK_IPK && pIter->abTblPk[iCol] ){
        /* If the target table column is an "INTEGER PRIMARY KEY", add
        ** "PRIMARY KEY" to the imposter table column declaration. */
        zPk = "PRIMARY KEY ";
      }
      zSql = rbuMPrintf(p, "%z%s\"%w\" %s %sCOLLATE %s%s", 
          zSql, zComma, zCol, pIter->azTblType[iCol], zPk, zColl,
          (pIter->abNotNull[iCol] ? " NOT NULL" : "")
      );
      zComma = ", ";
    }

    if( pIter->eType==RBU_PK_WITHOUT_ROWID ){
      char *zPk = rbuWithoutRowidPK(p, pIter);
      if( zPk ){
        zSql = rbuMPrintf(p, "%z, %z", zSql, zPk);
      }
    }

    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 1, tnum);
    rbuMPrintfExec(p, p->dbMain, "CREATE TABLE \"rbu_imp_%w\"(%z)%s", 
        pIter->zTbl, zSql, 
        (pIter->eType==RBU_PK_WITHOUT_ROWID ? " WITHOUT ROWID" : "")
    );
    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 0);
  }
}

/*
** Prepare a statement used to insert rows into the "rbu_tmp_xxx" table.
** Specifically a statement of the form:
**
**     INSERT INTO rbu_tmp_xxx VALUES(?, ?, ? ...);
**
** The number of bound variables is equal to the number of columns in
** the target table, plus one (for the rbu_control column), plus one more 
** (for the rbu_rowid column) if the target table is an implicit IPK or 
** virtual table.
*/
static void rbuObjIterPrepareTmpInsert(
  sqlite3rbu *p, 
  RbuObjIter *pIter,
  const char *zCollist,
  const char *zRbuRowid
){
  int bRbuRowid = (pIter->eType==RBU_PK_EXTERNAL || pIter->eType==RBU_PK_NONE);
  char *zBind = rbuObjIterGetBindlist(p, pIter->nTblCol + 1 + bRbuRowid);
  if( zBind ){
    assert( pIter->pTmpInsert==0 );
    p->rc = prepareFreeAndCollectError(
        p->dbRbu, &pIter->pTmpInsert, &p->zErrmsg, sqlite3_mprintf(
          "INSERT INTO %s.'rbu_tmp_%q'(rbu_control,%s%s) VALUES(%z)", 
          p->zStateDb, pIter->zTbl, zCollist, zRbuRowid, zBind
    ));
  }
}

static void rbuTmpInsertFunc(
  sqlite3_context *pCtx, 
  int nVal,
  sqlite3_value **apVal
){
  sqlite3rbu *p = sqlite3_user_data(pCtx);
  int rc = SQLITE_OK;
  int i;

  for(i=0; rc==SQLITE_OK && i<nVal; i++){
    rc = sqlite3_bind_value(p->objiter.pTmpInsert, i+1, apVal[i]);
  }
  if( rc==SQLITE_OK ){
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}

/*
** Ensure that the SQLite statement handles required to update the 
** target database object currently indicated by the iterator passed 
** as the second argument are available.
*/
static int otaObjIterPrepareAll(
  sqlite3ota *p, 
  OtaObjIter *pIter,
  int nOffset                     /* Add "LIMIT -1 OFFSET $nOffset" to SELECT */
){
  assert( pIter->bCleanup==0 );
  if( pIter->pSelect==0 && otaObjIterCacheTableInfo(p, pIter)==SQLITE_OK ){
    const int tnum = pIter->iTnum;
    char *zCollist = 0;           /* List of indexed columns */
    char **pz = &p->zErrmsg;
    const char *zIdx = pIter->zIdx;
    char *zLimit = 0;

    if( nOffset ){
      zLimit = sqlite3_mprintf(" LIMIT -1 OFFSET %d", nOffset);
      if( !zLimit ) p->rc = SQLITE_NOMEM;
    }

    if( zIdx ){
      const char *zTbl = pIter->zTbl;
      char *zImposterCols = 0;    /* Columns for imposter table */
      char *zImposterPK = 0;      /* Primary key declaration for imposter */
      char *zWhere = 0;           /* WHERE clause on PK columns */
      char *zBind = 0;
      int nBind = 0;

      assert( pIter->eType!=OTA_PK_VTAB );
      zCollist = otaObjIterGetIndexCols(
          p, pIter, &zImposterCols, &zImposterPK, &zWhere, &nBind
      );
      zBind = otaObjIterGetBindlist(p, nBind);

      /* Create the imposter table used to write to this index. */
      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 1);
      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 1,tnum);
      otaMPrintfExec(p, p->dbMain,
          "CREATE TABLE \"ota_imp_%w\"( %s, PRIMARY KEY( %s ) ) WITHOUT ROWID",
          zTbl, zImposterCols, zImposterPK
      );
      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 0);

      /* Create the statement to insert index entries */
      pIter->nCol = nBind;
      if( p->rc==SQLITE_OK ){
        p->rc = prepareFreeAndCollectError(
            p->dbMain, &pIter->pInsert, &p->zErrmsg,
          sqlite3_mprintf("INSERT INTO \"ota_imp_%w\" VALUES(%s)", zTbl, zBind)
        );
      }

      /* And to delete index entries */
      if( p->rc==SQLITE_OK ){
        p->rc = prepareFreeAndCollectError(
            p->dbMain, &pIter->pDelete, &p->zErrmsg,
          sqlite3_mprintf("DELETE FROM \"ota_imp_%w\" WHERE %s", zTbl, zWhere)
        );
      }

      /* Create the SELECT statement to read keys in sorted order */
      if( p->rc==SQLITE_OK ){
        char *zSql;
        if( pIter->eType==OTA_PK_EXTERNAL || pIter->eType==OTA_PK_NONE ){
          zSql = sqlite3_mprintf(
              "SELECT %s, ota_control FROM %s.'ota_tmp_%q' ORDER BY %s%s",
              zCollist, p->zStateDb, pIter->zTbl,
              zCollist, zLimit
          );
        }else{
          zSql = sqlite3_mprintf(
              "SELECT %s, ota_control FROM 'data_%q' "
              "WHERE typeof(ota_control)='integer' AND ota_control!=1 "
              "UNION ALL "
              "SELECT %s, ota_control FROM %s.'ota_tmp_%q' "
              "ORDER BY %s%s",
              zCollist, pIter->zTbl, 
              zCollist, p->zStateDb, pIter->zTbl, 
              zCollist, zLimit
          );
        }
        p->rc = prepareFreeAndCollectError(p->dbOta, &pIter->pSelect, pz, zSql);
      }

      sqlite3_free(zImposterCols);
      sqlite3_free(zImposterPK);
      sqlite3_free(zWhere);
      sqlite3_free(zBind);
    }else{
      int bOtaRowid = (pIter->eType==OTA_PK_VTAB || pIter->eType==OTA_PK_NONE);
      const char *zTbl = pIter->zTbl;       /* Table this step applies to */
      const char *zWrite;                   /* Imposter table name */

      char *zBindings = otaObjIterGetBindlist(p, pIter->nTblCol + bOtaRowid);
      char *zWhere = otaObjIterGetWhere(p, pIter);
      char *zOldlist = otaObjIterGetOldlist(p, pIter, "old");
      char *zNewlist = otaObjIterGetOldlist(p, pIter, "new");

      zCollist = otaObjIterGetCollist(p, pIter);
      pIter->nCol = pIter->nTblCol;

      /* Create the SELECT statement to read keys from data_xxx */
      if( p->rc==SQLITE_OK ){
        p->rc = prepareFreeAndCollectError(p->dbOta, &pIter->pSelect, pz,
            sqlite3_mprintf(
              "SELECT %s, ota_control%s FROM 'data_%q'%s", 
              zCollist, (bOtaRowid ? ", ota_rowid" : ""), zTbl, zLimit
            )
        );
      }

      /* Create the imposter table or tables (if required). */
      otaCreateImposterTable(p, pIter);
      otaCreateImposterTable2(p, pIter);
      zWrite = (pIter->eType==OTA_PK_VTAB ? "" : "ota_imp_");

      /* Create the INSERT statement to write to the target PK b-tree */
      if( p->rc==SQLITE_OK ){
        p->rc = prepareFreeAndCollectError(p->dbMain, &pIter->pInsert, pz,
            sqlite3_mprintf(
              "INSERT INTO \"%s%w\"(%s%s) VALUES(%s)", 
              zWrite, zTbl, zCollist, (bOtaRowid ? ", _rowid_" : ""), zBindings
            )
        );
      }

      /* Create the DELETE statement to write to the target PK b-tree */
      if( p->rc==SQLITE_OK ){
        p->rc = prepareFreeAndCollectError(p->dbMain, &pIter->pDelete, pz,
            sqlite3_mprintf(
              "DELETE FROM \"%s%w\" WHERE %s", zWrite, zTbl, zWhere
            )
        );
      }

      if( pIter->abIndexed ){
        const char *zOtaRowid = "";
        if( pIter->eType==OTA_PK_EXTERNAL || pIter->eType==OTA_PK_NONE ){
          zOtaRowid = ", ota_rowid";
        }

        /* Create the ota_tmp_xxx table and the triggers to populate it. */
        otaMPrintfExec(p, p->dbOta,
            "CREATE TABLE IF NOT EXISTS %s.'ota_tmp_%q' AS "
            "SELECT *%s FROM 'data_%q' WHERE 0;"
            , p->zStateDb
            , zTbl, (pIter->eType==OTA_PK_EXTERNAL ? ", 0 AS ota_rowid" : "")
            , zTbl
        );

        otaMPrintfExec(p, p->dbMain,
            "CREATE TEMP TRIGGER ota_delete_tr BEFORE DELETE ON \"%s%w\" "
            "BEGIN "
            "  SELECT ota_tmp_insert(2, %s);"
            "END;"

            "CREATE TEMP TRIGGER ota_update1_tr BEFORE UPDATE ON \"%s%w\" "
            "BEGIN "
            "  SELECT ota_tmp_insert(2, %s);"
            "END;"

            "CREATE TEMP TRIGGER ota_update2_tr AFTER UPDATE ON \"%s%w\" "
            "BEGIN "
            "  SELECT ota_tmp_insert(3, %s);"
            "END;",
            zWrite, zTbl, zOldlist,
            zWrite, zTbl, zOldlist,
            zWrite, zTbl, zNewlist
        );

        if( pIter->eType==OTA_PK_EXTERNAL || pIter->eType==OTA_PK_NONE ){
          otaMPrintfExec(p, p->dbMain,
              "CREATE TEMP TRIGGER ota_insert_tr AFTER INSERT ON \"%s%w\" "
              "BEGIN "
              "  SELECT ota_tmp_insert(0, %s);"
              "END;",
              zWrite, zTbl, zNewlist
          );
        }

        otaObjIterPrepareTmpInsert(p, pIter, zCollist, zOtaRowid);
      }

      sqlite3_free(zWhere);
      sqlite3_free(zOldlist);
      sqlite3_free(zNewlist);
      sqlite3_free(zBindings);
    }
    sqlite3_free(zCollist);
    sqlite3_free(zLimit);
  }
  
  return p->rc;
}

/*
** Set output variable *ppStmt to point to an UPDATE statement that may
** be used to update the imposter table for the main table b-tree of the
** table object that pIter currently points to, assuming that the 
** ota_control column of the data_xyz table contains zMask.
** 
** If the zMask string does not specify any columns to update, then this
** is not an error. Output variable *ppStmt is set to NULL in this case.
*/
static int otaGetUpdateStmt(
  sqlite3ota *p,                  /* OTA handle */
  OtaObjIter *pIter,              /* Object iterator */
  const char *zMask,              /* ota_control value ('x.x.') */
  sqlite3_stmt **ppStmt           /* OUT: UPDATE statement handle */
){
  OtaUpdateStmt **pp;
  OtaUpdateStmt *pUp = 0;
  int nUp = 0;

  /* In case an error occurs */
  *ppStmt = 0;

  /* Search for an existing statement. If one is found, shift it to the front
  ** of the LRU queue and return immediately. Otherwise, leave nUp pointing
  ** to the number of statements currently in the cache and pUp to the
  ** last object in the list.  */
  for(pp=&pIter->pOtaUpdate; *pp; pp=&((*pp)->pNext)){
    pUp = *pp;
    if( strcmp(pUp->zMask, zMask)==0 ){
      *pp = pUp->pNext;
      pUp->pNext = pIter->pOtaUpdate;
      pIter->pOtaUpdate = pUp;
      *ppStmt = pUp->pUpdate; 
      return SQLITE_OK;
    }
    nUp++;
  }
  assert( pUp==0 || pUp->pNext==0 );

  if( nUp>=SQLITE_OTA_UPDATE_CACHESIZE ){
    for(pp=&pIter->pOtaUpdate; *pp!=pUp; pp=&((*pp)->pNext));
    *pp = 0;
    sqlite3_finalize(pUp->pUpdate);
    pUp->pUpdate = 0;
  }else{
    pUp = (OtaUpdateStmt*)otaMalloc(p, sizeof(OtaUpdateStmt)+pIter->nTblCol+1);
  }

  if( pUp ){
    char *zWhere = otaObjIterGetWhere(p, pIter);
    char *zSet = otaObjIterGetSetlist(p, pIter, zMask);
    char *zUpdate = 0;

    pUp->zMask = (char*)&pUp[1];
    memcpy(pUp->zMask, zMask, pIter->nTblCol);
    pUp->pNext = pIter->pOtaUpdate;
    pIter->pOtaUpdate = pUp;

    if( zSet ){
      const char *zPrefix = "";

      if( pIter->eType!=OTA_PK_VTAB ) zPrefix = "ota_imp_";
      zUpdate = sqlite3_mprintf("UPDATE \"%s%w\" SET %s WHERE %s", 
          zPrefix, pIter->zTbl, zSet, zWhere
      );
      p->rc = prepareFreeAndCollectError(
          p->dbMain, &pUp->pUpdate, &p->zErrmsg, zUpdate
      );
      *ppStmt = pUp->pUpdate;
    }
    sqlite3_free(zWhere);
    sqlite3_free(zSet);
  }

  return p->rc;
}

static sqlite3 *otaOpenDbhandle(sqlite3ota *p, const char *zName){
  sqlite3 *db = 0;
  if( p->rc==SQLITE_OK ){
    const int flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|SQLITE_OPEN_URI;
    p->rc = sqlite3_open_v2(zName, &db, flags, p->zVfsName);
    if( p->rc ){
      p->zErrmsg = sqlite3_mprintf("%s", sqlite3_errmsg(db));
      sqlite3_close(db);
      db = 0;
    }
  }
  return db;
}

/*
** Open the database handle and attach the OTA database as "ota". If an
** error occurs, leave an error code and message in the OTA handle.
*/
static void otaOpenDatabase(sqlite3ota *p){
  assert( p->rc==SQLITE_OK );
  assert( p->dbMain==0 && p->dbOta==0 );

  p->eStage = 0;
  p->dbMain = otaOpenDbhandle(p, p->zTarget);
  p->dbOta = otaOpenDbhandle(p, p->zOta);

  /* If using separate OTA and state databases, attach the state database to
  ** the OTA db handle now.  */
  if( p->zState ){
    otaMPrintfExec(p, p->dbOta, "ATTACH %Q AS stat", p->zState);
    memcpy(p->zStateDb, "stat", 4);
  }else{
    memcpy(p->zStateDb, "main", 4);
  }

  if( p->rc==SQLITE_OK ){
    p->rc = sqlite3_create_function(p->dbMain, 
        "ota_tmp_insert", -1, SQLITE_UTF8, (void*)p, otaTmpInsertFunc, 0, 0
    );
  }

  if( p->rc==SQLITE_OK ){
    p->rc = sqlite3_file_control(p->dbMain, "main", SQLITE_FCNTL_OTA, (void*)p);
  }
  otaMPrintfExec(p, p->dbMain, "SELECT * FROM sqlite_master");

  /* Mark the database file just opened as an OTA target database. If 
  ** this call returns SQLITE_NOTFOUND, then the OTA vfs is not in use.
  ** This is an error.  */
  if( p->rc==SQLITE_OK ){
    p->rc = sqlite3_file_control(p->dbMain, "main", SQLITE_FCNTL_OTA, (void*)p);
  }

  if( p->rc==SQLITE_NOTFOUND ){
    p->rc = SQLITE_ERROR;
    p->zErrmsg = sqlite3_mprintf("ota vfs not found");
  }
}

/*
** This routine is a copy of the sqlite3FileSuffix3() routine from the core.
** It is a no-op unless SQLITE_ENABLE_8_3_NAMES is defined.
**







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}

/*
** Ensure that the SQLite statement handles required to update the 
** target database object currently indicated by the iterator passed 
** as the second argument are available.
*/
static int rbuObjIterPrepareAll(
  sqlite3rbu *p, 
  RbuObjIter *pIter,
  int nOffset                     /* Add "LIMIT -1 OFFSET $nOffset" to SELECT */
){
  assert( pIter->bCleanup==0 );
  if( pIter->pSelect==0 && rbuObjIterCacheTableInfo(p, pIter)==SQLITE_OK ){
    const int tnum = pIter->iTnum;
    char *zCollist = 0;           /* List of indexed columns */
    char **pz = &p->zErrmsg;
    const char *zIdx = pIter->zIdx;
    char *zLimit = 0;

    if( nOffset ){
      zLimit = sqlite3_mprintf(" LIMIT -1 OFFSET %d", nOffset);
      if( !zLimit ) p->rc = SQLITE_NOMEM;
    }

    if( zIdx ){
      const char *zTbl = pIter->zTbl;
      char *zImposterCols = 0;    /* Columns for imposter table */
      char *zImposterPK = 0;      /* Primary key declaration for imposter */
      char *zWhere = 0;           /* WHERE clause on PK columns */
      char *zBind = 0;
      int nBind = 0;

      assert( pIter->eType!=RBU_PK_VTAB );
      zCollist = rbuObjIterGetIndexCols(
          p, pIter, &zImposterCols, &zImposterPK, &zWhere, &nBind
      );
      zBind = rbuObjIterGetBindlist(p, nBind);

      /* Create the imposter table used to write to this index. */
      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 1);
      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 1,tnum);
      rbuMPrintfExec(p, p->dbMain,
          "CREATE TABLE \"rbu_imp_%w\"( %s, PRIMARY KEY( %s ) ) WITHOUT ROWID",
          zTbl, zImposterCols, zImposterPK
      );
      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 0);

      /* Create the statement to insert index entries */
      pIter->nCol = nBind;
      if( p->rc==SQLITE_OK ){
        p->rc = prepareFreeAndCollectError(
            p->dbMain, &pIter->pInsert, &p->zErrmsg,
          sqlite3_mprintf("INSERT INTO \"rbu_imp_%w\" VALUES(%s)", zTbl, zBind)
        );
      }

      /* And to delete index entries */
      if( p->rc==SQLITE_OK ){
        p->rc = prepareFreeAndCollectError(
            p->dbMain, &pIter->pDelete, &p->zErrmsg,
          sqlite3_mprintf("DELETE FROM \"rbu_imp_%w\" WHERE %s", zTbl, zWhere)
        );
      }

      /* Create the SELECT statement to read keys in sorted order */
      if( p->rc==SQLITE_OK ){
        char *zSql;
        if( pIter->eType==RBU_PK_EXTERNAL || pIter->eType==RBU_PK_NONE ){
          zSql = sqlite3_mprintf(
              "SELECT %s, rbu_control FROM %s.'rbu_tmp_%q' ORDER BY %s%s",
              zCollist, p->zStateDb, pIter->zTbl,
              zCollist, zLimit
          );
        }else{
          zSql = sqlite3_mprintf(
              "SELECT %s, rbu_control FROM 'data_%q' "
              "WHERE typeof(rbu_control)='integer' AND rbu_control!=1 "
              "UNION ALL "
              "SELECT %s, rbu_control FROM %s.'rbu_tmp_%q' "
              "ORDER BY %s%s",
              zCollist, pIter->zTbl, 
              zCollist, p->zStateDb, pIter->zTbl, 
              zCollist, zLimit
          );
        }
        p->rc = prepareFreeAndCollectError(p->dbRbu, &pIter->pSelect, pz, zSql);
      }

      sqlite3_free(zImposterCols);
      sqlite3_free(zImposterPK);
      sqlite3_free(zWhere);
      sqlite3_free(zBind);
    }else{
      int bRbuRowid = (pIter->eType==RBU_PK_VTAB || pIter->eType==RBU_PK_NONE);
      const char *zTbl = pIter->zTbl;       /* Table this step applies to */
      const char *zWrite;                   /* Imposter table name */

      char *zBindings = rbuObjIterGetBindlist(p, pIter->nTblCol + bRbuRowid);
      char *zWhere = rbuObjIterGetWhere(p, pIter);
      char *zOldlist = rbuObjIterGetOldlist(p, pIter, "old");
      char *zNewlist = rbuObjIterGetOldlist(p, pIter, "new");

      zCollist = rbuObjIterGetCollist(p, pIter);
      pIter->nCol = pIter->nTblCol;

      /* Create the SELECT statement to read keys from data_xxx */
      if( p->rc==SQLITE_OK ){
        p->rc = prepareFreeAndCollectError(p->dbRbu, &pIter->pSelect, pz,
            sqlite3_mprintf(
              "SELECT %s, rbu_control%s FROM 'data_%q'%s", 
              zCollist, (bRbuRowid ? ", rbu_rowid" : ""), zTbl, zLimit
            )
        );
      }

      /* Create the imposter table or tables (if required). */
      rbuCreateImposterTable(p, pIter);
      rbuCreateImposterTable2(p, pIter);
      zWrite = (pIter->eType==RBU_PK_VTAB ? "" : "rbu_imp_");

      /* Create the INSERT statement to write to the target PK b-tree */
      if( p->rc==SQLITE_OK ){
        p->rc = prepareFreeAndCollectError(p->dbMain, &pIter->pInsert, pz,
            sqlite3_mprintf(
              "INSERT INTO \"%s%w\"(%s%s) VALUES(%s)", 
              zWrite, zTbl, zCollist, (bRbuRowid ? ", _rowid_" : ""), zBindings
            )
        );
      }

      /* Create the DELETE statement to write to the target PK b-tree */
      if( p->rc==SQLITE_OK ){
        p->rc = prepareFreeAndCollectError(p->dbMain, &pIter->pDelete, pz,
            sqlite3_mprintf(
              "DELETE FROM \"%s%w\" WHERE %s", zWrite, zTbl, zWhere
            )
        );
      }

      if( pIter->abIndexed ){
        const char *zRbuRowid = "";
        if( pIter->eType==RBU_PK_EXTERNAL || pIter->eType==RBU_PK_NONE ){
          zRbuRowid = ", rbu_rowid";
        }

        /* Create the rbu_tmp_xxx table and the triggers to populate it. */
        rbuMPrintfExec(p, p->dbRbu,
            "CREATE TABLE IF NOT EXISTS %s.'rbu_tmp_%q' AS "
            "SELECT *%s FROM 'data_%q' WHERE 0;"
            , p->zStateDb
            , zTbl, (pIter->eType==RBU_PK_EXTERNAL ? ", 0 AS rbu_rowid" : "")
            , zTbl
        );

        rbuMPrintfExec(p, p->dbMain,
            "CREATE TEMP TRIGGER rbu_delete_tr BEFORE DELETE ON \"%s%w\" "
            "BEGIN "
            "  SELECT rbu_tmp_insert(2, %s);"
            "END;"

            "CREATE TEMP TRIGGER rbu_update1_tr BEFORE UPDATE ON \"%s%w\" "
            "BEGIN "
            "  SELECT rbu_tmp_insert(2, %s);"
            "END;"

            "CREATE TEMP TRIGGER rbu_update2_tr AFTER UPDATE ON \"%s%w\" "
            "BEGIN "
            "  SELECT rbu_tmp_insert(3, %s);"
            "END;",
            zWrite, zTbl, zOldlist,
            zWrite, zTbl, zOldlist,
            zWrite, zTbl, zNewlist
        );

        if( pIter->eType==RBU_PK_EXTERNAL || pIter->eType==RBU_PK_NONE ){
          rbuMPrintfExec(p, p->dbMain,
              "CREATE TEMP TRIGGER rbu_insert_tr AFTER INSERT ON \"%s%w\" "
              "BEGIN "
              "  SELECT rbu_tmp_insert(0, %s);"
              "END;",
              zWrite, zTbl, zNewlist
          );
        }

        rbuObjIterPrepareTmpInsert(p, pIter, zCollist, zRbuRowid);
      }

      sqlite3_free(zWhere);
      sqlite3_free(zOldlist);
      sqlite3_free(zNewlist);
      sqlite3_free(zBindings);
    }
    sqlite3_free(zCollist);
    sqlite3_free(zLimit);
  }
  
  return p->rc;
}

/*
** Set output variable *ppStmt to point to an UPDATE statement that may
** be used to update the imposter table for the main table b-tree of the
** table object that pIter currently points to, assuming that the 
** rbu_control column of the data_xyz table contains zMask.
** 
** If the zMask string does not specify any columns to update, then this
** is not an error. Output variable *ppStmt is set to NULL in this case.
*/
static int rbuGetUpdateStmt(
  sqlite3rbu *p,                  /* RBU handle */
  RbuObjIter *pIter,              /* Object iterator */
  const char *zMask,              /* rbu_control value ('x.x.') */
  sqlite3_stmt **ppStmt           /* OUT: UPDATE statement handle */
){
  RbuUpdateStmt **pp;
  RbuUpdateStmt *pUp = 0;
  int nUp = 0;

  /* In case an error occurs */
  *ppStmt = 0;

  /* Search for an existing statement. If one is found, shift it to the front
  ** of the LRU queue and return immediately. Otherwise, leave nUp pointing
  ** to the number of statements currently in the cache and pUp to the
  ** last object in the list.  */
  for(pp=&pIter->pRbuUpdate; *pp; pp=&((*pp)->pNext)){
    pUp = *pp;
    if( strcmp(pUp->zMask, zMask)==0 ){
      *pp = pUp->pNext;
      pUp->pNext = pIter->pRbuUpdate;
      pIter->pRbuUpdate = pUp;
      *ppStmt = pUp->pUpdate; 
      return SQLITE_OK;
    }
    nUp++;
  }
  assert( pUp==0 || pUp->pNext==0 );

  if( nUp>=SQLITE_RBU_UPDATE_CACHESIZE ){
    for(pp=&pIter->pRbuUpdate; *pp!=pUp; pp=&((*pp)->pNext));
    *pp = 0;
    sqlite3_finalize(pUp->pUpdate);
    pUp->pUpdate = 0;
  }else{
    pUp = (RbuUpdateStmt*)rbuMalloc(p, sizeof(RbuUpdateStmt)+pIter->nTblCol+1);
  }

  if( pUp ){
    char *zWhere = rbuObjIterGetWhere(p, pIter);
    char *zSet = rbuObjIterGetSetlist(p, pIter, zMask);
    char *zUpdate = 0;

    pUp->zMask = (char*)&pUp[1];
    memcpy(pUp->zMask, zMask, pIter->nTblCol);
    pUp->pNext = pIter->pRbuUpdate;
    pIter->pRbuUpdate = pUp;

    if( zSet ){
      const char *zPrefix = "";

      if( pIter->eType!=RBU_PK_VTAB ) zPrefix = "rbu_imp_";
      zUpdate = sqlite3_mprintf("UPDATE \"%s%w\" SET %s WHERE %s", 
          zPrefix, pIter->zTbl, zSet, zWhere
      );
      p->rc = prepareFreeAndCollectError(
          p->dbMain, &pUp->pUpdate, &p->zErrmsg, zUpdate
      );
      *ppStmt = pUp->pUpdate;
    }
    sqlite3_free(zWhere);
    sqlite3_free(zSet);
  }

  return p->rc;
}

static sqlite3 *rbuOpenDbhandle(sqlite3rbu *p, const char *zName){
  sqlite3 *db = 0;
  if( p->rc==SQLITE_OK ){
    const int flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|SQLITE_OPEN_URI;
    p->rc = sqlite3_open_v2(zName, &db, flags, p->zVfsName);
    if( p->rc ){
      p->zErrmsg = sqlite3_mprintf("%s", sqlite3_errmsg(db));
      sqlite3_close(db);
      db = 0;
    }
  }
  return db;
}

/*
** Open the database handle and attach the RBU database as "rbu". If an
** error occurs, leave an error code and message in the RBU handle.
*/
static void rbuOpenDatabase(sqlite3rbu *p){
  assert( p->rc==SQLITE_OK );
  assert( p->dbMain==0 && p->dbRbu==0 );

  p->eStage = 0;
  p->dbMain = rbuOpenDbhandle(p, p->zTarget);
  p->dbRbu = rbuOpenDbhandle(p, p->zRbu);

  /* If using separate RBU and state databases, attach the state database to
  ** the RBU db handle now.  */
  if( p->zState ){
    rbuMPrintfExec(p, p->dbRbu, "ATTACH %Q AS stat", p->zState);
    memcpy(p->zStateDb, "stat", 4);
  }else{
    memcpy(p->zStateDb, "main", 4);
  }

  if( p->rc==SQLITE_OK ){
    p->rc = sqlite3_create_function(p->dbMain, 
        "rbu_tmp_insert", -1, SQLITE_UTF8, (void*)p, rbuTmpInsertFunc, 0, 0
    );
  }

  if( p->rc==SQLITE_OK ){
    p->rc = sqlite3_file_control(p->dbMain, "main", SQLITE_FCNTL_RBU, (void*)p);
  }
  rbuMPrintfExec(p, p->dbMain, "SELECT * FROM sqlite_master");

  /* Mark the database file just opened as an RBU target database. If 
  ** this call returns SQLITE_NOTFOUND, then the RBU vfs is not in use.
  ** This is an error.  */
  if( p->rc==SQLITE_OK ){
    p->rc = sqlite3_file_control(p->dbMain, "main", SQLITE_FCNTL_RBU, (void*)p);
  }

  if( p->rc==SQLITE_NOTFOUND ){
    p->rc = SQLITE_ERROR;
    p->zErrmsg = sqlite3_mprintf("rbu vfs not found");
  }
}

/*
** This routine is a copy of the sqlite3FileSuffix3() routine from the core.
** It is a no-op unless SQLITE_ENABLE_8_3_NAMES is defined.
**
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** Examples:
**
**     test.db-journal    =>   test.nal
**     test.db-wal        =>   test.wal
**     test.db-shm        =>   test.shm
**     test.db-mj7f3319fa =>   test.9fa
*/
static void otaFileSuffix3(const char *zBase, char *z){
#ifdef SQLITE_ENABLE_8_3_NAMES
#if SQLITE_ENABLE_8_3_NAMES<2
  if( sqlite3_uri_boolean(zBase, "8_3_names", 0) )
#endif
  {
    int i, sz;
    sz = sqlite3Strlen30(z);
    for(i=sz-1; i>0 && z[i]!='/' && z[i]!='.'; i--){}
    if( z[i]=='.' && ALWAYS(sz>i+4) ) memmove(&z[i+1], &z[sz-3], 4);
  }
#endif
}

/*
** Return the current wal-index header checksum for the target database 
** as a 64-bit integer.
**
** The checksum is store in the first page of xShmMap memory as an 8-byte 
** blob starting at byte offset 40.
*/
static i64 otaShmChecksum(sqlite3ota *p){
  i64 iRet = 0;
  if( p->rc==SQLITE_OK ){
    sqlite3_file *pDb = p->pTargetFd->pReal;
    u32 volatile *ptr;
    p->rc = pDb->pMethods->xShmMap(pDb, 0, 32*1024, 0, (void volatile**)&ptr);
    if( p->rc==SQLITE_OK ){
      iRet = ((i64)ptr[10] << 32) + ptr[11];
    }
  }
  return iRet;
}

/*
** This function is called as part of initializing or reinitializing an
** incremental checkpoint. 
**
** It populates the sqlite3ota.aFrame[] array with the set of 
** (wal frame -> db page) copy operations required to checkpoint the 
** current wal file, and obtains the set of shm locks required to safely 
** perform the copy operations directly on the file-system.
**
** If argument pState is not NULL, then the incremental checkpoint is
** being resumed. In this case, if the checksum of the wal-index-header
** following recovery is not the same as the checksum saved in the OtaState
** object, then the ota handle is set to DONE state. This occurs if some
** other client appends a transaction to the wal file in the middle of
** an incremental checkpoint.
*/
static void otaSetupCheckpoint(sqlite3ota *p, OtaState *pState){

  /* If pState is NULL, then the wal file may not have been opened and
  ** recovered. Running a read-statement here to ensure that doing so
  ** does not interfere with the "capture" process below.  */
  if( pState==0 ){
    p->eStage = 0;
    if( p->rc==SQLITE_OK ){
      p->rc = sqlite3_exec(p->dbMain, "SELECT * FROM sqlite_master", 0, 0, 0);
    }
  }

  /* Assuming no error has occurred, run a "restart" checkpoint with the
  ** sqlite3ota.eStage variable set to CAPTURE. This turns on the following
  ** special behaviour in the ota VFS:
  **
  **   * If the exclusive shm WRITER or READ0 lock cannot be obtained,
  **     the checkpoint fails with SQLITE_BUSY (normally SQLite would
  **     proceed with running a passive checkpoint instead of failing).
  **
  **   * Attempts to read from the *-wal file or write to the database file
  **     do not perform any IO. Instead, the frame/page combinations that
  **     would be read/written are recorded in the sqlite3ota.aFrame[]
  **     array.
  **
  **   * Calls to xShmLock(UNLOCK) to release the exclusive shm WRITER, 
  **     READ0 and CHECKPOINT locks taken as part of the checkpoint are
  **     no-ops. These locks will not be released until the connection
  **     is closed.
  **
  **   * Attempting to xSync() the database file causes an SQLITE_INTERNAL 
  **     error.
  **
  ** As a result, unless an error (i.e. OOM or SQLITE_BUSY) occurs, the
  ** checkpoint below fails with SQLITE_INTERNAL, and leaves the aFrame[]
  ** array populated with a set of (frame -> page) mappings. Because the 
  ** WRITER, CHECKPOINT and READ0 locks are still held, it is safe to copy 
  ** data from the wal file into the database file according to the 
  ** contents of aFrame[].
  */
  if( p->rc==SQLITE_OK ){
    int rc2;
    p->eStage = OTA_STAGE_CAPTURE;
    rc2 = sqlite3_exec(p->dbMain, "PRAGMA main.wal_checkpoint=restart", 0, 0,0);
    if( rc2!=SQLITE_INTERNAL ) p->rc = rc2;
  }

  if( p->rc==SQLITE_OK ){
    p->eStage = OTA_STAGE_CKPT;
    p->nStep = (pState ? pState->nRow : 0);
    p->aBuf = otaMalloc(p, p->pgsz);
    p->iWalCksum = otaShmChecksum(p);
  }

  if( p->rc==SQLITE_OK && pState && pState->iWalCksum!=p->iWalCksum ){
    p->rc = SQLITE_DONE;
    p->eStage = OTA_STAGE_DONE;
  }
}

/*
** Called when iAmt bytes are read from offset iOff of the wal file while
** the ota object is in capture mode. Record the frame number of the frame
** being read in the aFrame[] array.
*/
static int otaCaptureWalRead(sqlite3ota *pOta, i64 iOff, int iAmt){
  const u32 mReq = (1<<WAL_LOCK_WRITE)|(1<<WAL_LOCK_CKPT)|(1<<WAL_LOCK_READ0);
  u32 iFrame;

  if( pOta->mLock!=mReq ){
    pOta->rc = SQLITE_BUSY;
    return SQLITE_INTERNAL;
  }

  pOta->pgsz = iAmt;
  if( pOta->nFrame==pOta->nFrameAlloc ){
    int nNew = (pOta->nFrameAlloc ? pOta->nFrameAlloc : 64) * 2;
    OtaFrame *aNew;
    aNew = (OtaFrame*)sqlite3_realloc(pOta->aFrame, nNew * sizeof(OtaFrame));
    if( aNew==0 ) return SQLITE_NOMEM;
    pOta->aFrame = aNew;
    pOta->nFrameAlloc = nNew;
  }

  iFrame = (u32)((iOff-32) / (i64)(iAmt+24)) + 1;
  if( pOta->iMaxFrame<iFrame ) pOta->iMaxFrame = iFrame;
  pOta->aFrame[pOta->nFrame].iWalFrame = iFrame;
  pOta->aFrame[pOta->nFrame].iDbPage = 0;
  pOta->nFrame++;
  return SQLITE_OK;
}

/*
** Called when a page of data is written to offset iOff of the database
** file while the ota handle is in capture mode. Record the page number 
** of the page being written in the aFrame[] array.
*/
static int otaCaptureDbWrite(sqlite3ota *pOta, i64 iOff){
  pOta->aFrame[pOta->nFrame-1].iDbPage = (u32)(iOff / pOta->pgsz) + 1;
  return SQLITE_OK;
}

/*
** This is called as part of an incremental checkpoint operation. Copy
** a single frame of data from the wal file into the database file, as
** indicated by the OtaFrame object.
*/
static void otaCheckpointFrame(sqlite3ota *p, OtaFrame *pFrame){
  sqlite3_file *pWal = p->pTargetFd->pWalFd->pReal;
  sqlite3_file *pDb = p->pTargetFd->pReal;
  i64 iOff;

  assert( p->rc==SQLITE_OK );
  iOff = (i64)(pFrame->iWalFrame-1) * (p->pgsz + 24) + 32 + 24;
  p->rc = pWal->pMethods->xRead(pWal, p->aBuf, p->pgsz, iOff);
  if( p->rc ) return;

  iOff = (i64)(pFrame->iDbPage-1) * p->pgsz;
  p->rc = pDb->pMethods->xWrite(pDb, p->aBuf, p->pgsz, iOff);
}


/*
** Take an EXCLUSIVE lock on the database file.
*/
static void otaLockDatabase(sqlite3ota *p){
  sqlite3_file *pReal = p->pTargetFd->pReal;
  assert( p->rc==SQLITE_OK );
  p->rc = pReal->pMethods->xLock(pReal, SQLITE_LOCK_SHARED);
  if( p->rc==SQLITE_OK ){
    p->rc = pReal->pMethods->xLock(pReal, SQLITE_LOCK_EXCLUSIVE);
  }
}

/*
** The OTA handle is currently in OTA_STAGE_OAL state, with a SHARED lock
** on the database file. This proc moves the *-oal file to the *-wal path,
** then reopens the database file (this time in vanilla, non-oal, WAL mode).
** If an error occurs, leave an error code and error message in the ota 
** handle.
*/
static void otaMoveOalFile(sqlite3ota *p){
  const char *zBase = sqlite3_db_filename(p->dbMain, "main");

  char *zWal = sqlite3_mprintf("%s-wal", zBase);
  char *zOal = sqlite3_mprintf("%s-oal", zBase);

  assert( p->eStage==OTA_STAGE_MOVE );
  assert( p->rc==SQLITE_OK && p->zErrmsg==0 );
  if( zWal==0 || zOal==0 ){
    p->rc = SQLITE_NOMEM;
  }else{
    /* Move the *-oal file to *-wal. At this point connection p->db is
    ** holding a SHARED lock on the target database file (because it is
    ** in WAL mode). So no other connection may be writing the db. 
    **
    ** In order to ensure that there are no database readers, an EXCLUSIVE
    ** lock is obtained here before the *-oal is moved to *-wal.
    */
    otaLockDatabase(p);
    if( p->rc==SQLITE_OK ){
      otaFileSuffix3(zBase, zWal);
      otaFileSuffix3(zBase, zOal);

      /* Re-open the databases. */
      otaObjIterFinalize(&p->objiter);
      sqlite3_close(p->dbMain);
      sqlite3_close(p->dbOta);
      p->rc = rename(zOal, zWal) ? SQLITE_IOERR : SQLITE_OK;
      if( p->rc==SQLITE_OK ){
        p->dbMain = 0;
        p->dbOta = 0;
        otaOpenDatabase(p);
        otaSetupCheckpoint(p, 0);
      }
    }
  }

  sqlite3_free(zWal);
  sqlite3_free(zOal);
}

/*
** The SELECT statement iterating through the keys for the current object
** (p->objiter.pSelect) currently points to a valid row. This function
** determines the type of operation requested by this row and returns
** one of the following values to indicate the result:
**
**     * OTA_INSERT
**     * OTA_DELETE
**     * OTA_IDX_DELETE
**     * OTA_UPDATE
**
** If OTA_UPDATE is returned, then output variable *pzMask is set to
** point to the text value indicating the columns to update.
**
** If the ota_control field contains an invalid value, an error code and
** message are left in the OTA handle and zero returned.
*/
static int otaStepType(sqlite3ota *p, const char **pzMask){
  int iCol = p->objiter.nCol;     /* Index of ota_control column */
  int res = 0;                    /* Return value */

  switch( sqlite3_column_type(p->objiter.pSelect, iCol) ){
    case SQLITE_INTEGER: {
      int iVal = sqlite3_column_int(p->objiter.pSelect, iCol);
      if( iVal==0 ){
        res = OTA_INSERT;
      }else if( iVal==1 ){
        res = OTA_DELETE;
      }else if( iVal==2 ){
        res = OTA_IDX_DELETE;
      }else if( iVal==3 ){
        res = OTA_IDX_INSERT;
      }
      break;
    }

    case SQLITE_TEXT: {
      const unsigned char *z = sqlite3_column_text(p->objiter.pSelect, iCol);
      if( z==0 ){
        p->rc = SQLITE_NOMEM;
      }else{
        *pzMask = (const char*)z;
      }
      res = OTA_UPDATE;

      break;
    }

    default:
      break;
  }

  if( res==0 ){
    otaBadControlError(p);
  }
  return res;
}

#ifdef SQLITE_DEBUG
/*
** Assert that column iCol of statement pStmt is named zName.
*/
static void assertColumnName(sqlite3_stmt *pStmt, int iCol, const char *zName){
  const char *zCol = sqlite3_column_name(pStmt, iCol);
  assert( 0==sqlite3_stricmp(zName, zCol) );
}
#else
# define assertColumnName(x,y,z)
#endif

/*
** This function does the work for an sqlite3ota_step() call.
**
** The object-iterator (p->objiter) currently points to a valid object,
** and the input cursor (p->objiter.pSelect) currently points to a valid
** input row. Perform whatever processing is required and return.
**
** If no  error occurs, SQLITE_OK is returned. Otherwise, an error code
** and message is left in the OTA handle and a copy of the error code
** returned.
*/
static int otaStep(sqlite3ota *p){
  OtaObjIter *pIter = &p->objiter;
  const char *zMask = 0;
  int i;
  int eType = otaStepType(p, &zMask);

  if( eType ){
    assert( eType!=OTA_UPDATE || pIter->zIdx==0 );

    if( pIter->zIdx==0 && eType==OTA_IDX_DELETE ){
      otaBadControlError(p);
    }
    else if( 
        eType==OTA_INSERT 
     || eType==OTA_DELETE
     || eType==OTA_IDX_DELETE 
     || eType==OTA_IDX_INSERT
    ){
      sqlite3_value *pVal;
      sqlite3_stmt *pWriter;

      assert( eType!=OTA_UPDATE );
      assert( eType!=OTA_DELETE || pIter->zIdx==0 );

      if( eType==OTA_IDX_DELETE || eType==OTA_DELETE ){
        pWriter = pIter->pDelete;
      }else{
        pWriter = pIter->pInsert;
      }

      for(i=0; i<pIter->nCol; i++){
        /* If this is an INSERT into a table b-tree and the table has an
        ** explicit INTEGER PRIMARY KEY, check that this is not an attempt
        ** to write a NULL into the IPK column. That is not permitted.  */
        if( eType==OTA_INSERT 
         && pIter->zIdx==0 && pIter->eType==OTA_PK_IPK && pIter->abTblPk[i] 
         && sqlite3_column_type(pIter->pSelect, i)==SQLITE_NULL
        ){
          p->rc = SQLITE_MISMATCH;
          p->zErrmsg = sqlite3_mprintf("datatype mismatch");
          goto step_out;
        }

        if( eType==OTA_DELETE && pIter->abTblPk[i]==0 ){
          continue;
        }

        pVal = sqlite3_column_value(pIter->pSelect, i);
        p->rc = sqlite3_bind_value(pWriter, i+1, pVal);
        if( p->rc ) goto step_out;
      }
      if( pIter->zIdx==0
       && (pIter->eType==OTA_PK_VTAB || pIter->eType==OTA_PK_NONE) 
      ){
        /* For a virtual table, or a table with no primary key, the 
        ** SELECT statement is:
        **
        **   SELECT <cols>, ota_control, ota_rowid FROM ....
        **
        ** Hence column_value(pIter->nCol+1).
        */
        assertColumnName(pIter->pSelect, pIter->nCol+1, "ota_rowid");
        pVal = sqlite3_column_value(pIter->pSelect, pIter->nCol+1);
        p->rc = sqlite3_bind_value(pWriter, pIter->nCol+1, pVal);
      }
      if( p->rc==SQLITE_OK ){
        sqlite3_step(pWriter);
        p->rc = resetAndCollectError(pWriter, &p->zErrmsg);
      }
    }else{
      sqlite3_value *pVal;
      sqlite3_stmt *pUpdate = 0;
      assert( eType==OTA_UPDATE );
      otaGetUpdateStmt(p, pIter, zMask, &pUpdate);
      if( pUpdate ){
        for(i=0; p->rc==SQLITE_OK && i<pIter->nCol; i++){
          char c = zMask[pIter->aiSrcOrder[i]];
          pVal = sqlite3_column_value(pIter->pSelect, i);
          if( pIter->abTblPk[i] || c=='x' || c=='d' ){
            p->rc = sqlite3_bind_value(pUpdate, i+1, pVal);
          }
        }
        if( p->rc==SQLITE_OK 
         && (pIter->eType==OTA_PK_VTAB || pIter->eType==OTA_PK_NONE) 
        ){
          /* Bind the ota_rowid value to column _rowid_ */
          assertColumnName(pIter->pSelect, pIter->nCol+1, "ota_rowid");
          pVal = sqlite3_column_value(pIter->pSelect, pIter->nCol+1);
          p->rc = sqlite3_bind_value(pUpdate, pIter->nCol+1, pVal);
        }
        if( p->rc==SQLITE_OK ){
          sqlite3_step(pUpdate);
          p->rc = resetAndCollectError(pUpdate, &p->zErrmsg);
        }
      }
    }
  }

 step_out:
  return p->rc;
}

/*
** Increment the schema cookie of the main database opened by p->dbMain.
*/
static void otaIncrSchemaCookie(sqlite3ota *p){
  if( p->rc==SQLITE_OK ){
    int iCookie = 1000000;
    sqlite3_stmt *pStmt;

    p->rc = prepareAndCollectError(p->dbMain, &pStmt, &p->zErrmsg, 
        "PRAGMA schema_version"
    );
    if( p->rc==SQLITE_OK ){
      /* Coverage: it may be that this sqlite3_step() cannot fail. There
      ** is already a transaction open, so the prepared statement cannot
      ** throw an SQLITE_SCHEMA exception. The only database page the
      ** statement reads is page 1, which is guaranteed to be in the cache.
      ** And no memory allocations are required.  */
      if( SQLITE_ROW==sqlite3_step(pStmt) ){
        iCookie = sqlite3_column_int(pStmt, 0);
      }
      otaFinalize(p, pStmt);
    }
    if( p->rc==SQLITE_OK ){
      otaMPrintfExec(p, p->dbMain, "PRAGMA schema_version = %d", iCookie+1);
    }
  }
}

/*
** Update the contents of the ota_state table within the ota database. The
** value stored in the OTA_STATE_STAGE column is eStage. All other values
** are determined by inspecting the ota handle passed as the first argument.
*/
static void otaSaveState(sqlite3ota *p, int eStage){
  if( p->rc==SQLITE_OK || p->rc==SQLITE_DONE ){
    sqlite3_stmt *pInsert = 0;
    int rc;

    assert( p->zErrmsg==0 );
    rc = prepareFreeAndCollectError(p->dbOta, &pInsert, &p->zErrmsg, 
        sqlite3_mprintf(
          "INSERT OR REPLACE INTO %s.ota_state(k, v) VALUES "
          "(%d, %d), "
          "(%d, %Q), "
          "(%d, %Q), "
          "(%d, %d), "
          "(%d, %d), "
          "(%d, %lld), "
          "(%d, %lld), "
          "(%d, %lld) ",
          p->zStateDb,
          OTA_STATE_STAGE, eStage,
          OTA_STATE_TBL, p->objiter.zTbl, 
          OTA_STATE_IDX, p->objiter.zIdx, 
          OTA_STATE_ROW, p->nStep, 
          OTA_STATE_PROGRESS, p->nProgress,
          OTA_STATE_CKPT, p->iWalCksum,
          OTA_STATE_COOKIE, (i64)p->pTargetFd->iCookie,
          OTA_STATE_OALSZ, p->iOalSz
      )
    );
    assert( pInsert==0 || rc==SQLITE_OK );

    if( rc==SQLITE_OK ){
      sqlite3_step(pInsert);
      rc = sqlite3_finalize(pInsert);
    }
    if( rc!=SQLITE_OK ) p->rc = rc;
  }
}


/*
** Step the OTA object.
*/
SQLITE_API int SQLITE_STDCALL sqlite3ota_step(sqlite3ota *p){
  if( p ){
    switch( p->eStage ){
      case OTA_STAGE_OAL: {
        OtaObjIter *pIter = &p->objiter;
        while( p->rc==SQLITE_OK && pIter->zTbl ){

          if( pIter->bCleanup ){
            /* Clean up the ota_tmp_xxx table for the previous table. It 
            ** cannot be dropped as there are currently active SQL statements.
            ** But the contents can be deleted.  */
            if( pIter->abIndexed ){
              otaMPrintfExec(p, p->dbOta, 
                  "DELETE FROM %s.'ota_tmp_%q'", p->zStateDb, pIter->zTbl
              );
            }
          }else{
            otaObjIterPrepareAll(p, pIter, 0);

            /* Advance to the next row to process. */
            if( p->rc==SQLITE_OK ){
              int rc = sqlite3_step(pIter->pSelect);
              if( rc==SQLITE_ROW ){
                p->nProgress++;
                p->nStep++;
                return otaStep(p);
              }
              p->rc = sqlite3_reset(pIter->pSelect);
              p->nStep = 0;
            }
          }

          otaObjIterNext(p, pIter);
        }

        if( p->rc==SQLITE_OK ){
          assert( pIter->zTbl==0 );
          otaSaveState(p, OTA_STAGE_MOVE);
          otaIncrSchemaCookie(p);
          if( p->rc==SQLITE_OK ){
            p->rc = sqlite3_exec(p->dbMain, "COMMIT", 0, 0, &p->zErrmsg);
          }
          if( p->rc==SQLITE_OK ){
            p->rc = sqlite3_exec(p->dbOta, "COMMIT", 0, 0, &p->zErrmsg);
          }
          p->eStage = OTA_STAGE_MOVE;
        }
        break;
      }

      case OTA_STAGE_MOVE: {
        if( p->rc==SQLITE_OK ){
          otaMoveOalFile(p);
          p->nProgress++;
        }
        break;
      }

      case OTA_STAGE_CKPT: {
        if( p->rc==SQLITE_OK ){
          if( p->nStep>=p->nFrame ){
            sqlite3_file *pDb = p->pTargetFd->pReal;
  
            /* Sync the db file */
            p->rc = pDb->pMethods->xSync(pDb, SQLITE_SYNC_NORMAL);
  
            /* Update nBackfill */
            if( p->rc==SQLITE_OK ){
              void volatile *ptr;
              p->rc = pDb->pMethods->xShmMap(pDb, 0, 32*1024, 0, &ptr);
              if( p->rc==SQLITE_OK ){
                ((u32 volatile*)ptr)[24] = p->iMaxFrame;
              }
            }
  
            if( p->rc==SQLITE_OK ){
              p->eStage = OTA_STAGE_DONE;
              p->rc = SQLITE_DONE;
            }
          }else{
            OtaFrame *pFrame = &p->aFrame[p->nStep];
            otaCheckpointFrame(p, pFrame);
            p->nStep++;
          }
          p->nProgress++;
        }
        break;
      }

      default:
        break;
    }
    return p->rc;
  }else{
    return SQLITE_NOMEM;
  }
}

/*
** Free an OtaState object allocated by otaLoadState().
*/
static void otaFreeState(OtaState *p){
  if( p ){
    sqlite3_free(p->zTbl);
    sqlite3_free(p->zIdx);
    sqlite3_free(p);
  }
}

/*
** Allocate an OtaState object and load the contents of the ota_state 
** table into it. Return a pointer to the new object. It is the 
** responsibility of the caller to eventually free the object using
** sqlite3_free().
**
** If an error occurs, leave an error code and message in the ota handle
** and return NULL.
*/
static OtaState *otaLoadState(sqlite3ota *p){
  OtaState *pRet = 0;
  sqlite3_stmt *pStmt = 0;
  int rc;
  int rc2;

  pRet = (OtaState*)otaMalloc(p, sizeof(OtaState));
  if( pRet==0 ) return 0;

  rc = prepareFreeAndCollectError(p->dbOta, &pStmt, &p->zErrmsg, 
      sqlite3_mprintf("SELECT k, v FROM %s.ota_state", p->zStateDb)
  );
  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
    switch( sqlite3_column_int(pStmt, 0) ){
      case OTA_STATE_STAGE:
        pRet->eStage = sqlite3_column_int(pStmt, 1);
        if( pRet->eStage!=OTA_STAGE_OAL
         && pRet->eStage!=OTA_STAGE_MOVE
         && pRet->eStage!=OTA_STAGE_CKPT
        ){
          p->rc = SQLITE_CORRUPT;
        }
        break;

      case OTA_STATE_TBL:
        pRet->zTbl = otaStrndup((char*)sqlite3_column_text(pStmt, 1), &rc);
        break;

      case OTA_STATE_IDX:
        pRet->zIdx = otaStrndup((char*)sqlite3_column_text(pStmt, 1), &rc);
        break;

      case OTA_STATE_ROW:
        pRet->nRow = sqlite3_column_int(pStmt, 1);
        break;

      case OTA_STATE_PROGRESS:
        pRet->nProgress = sqlite3_column_int64(pStmt, 1);
        break;

      case OTA_STATE_CKPT:
        pRet->iWalCksum = sqlite3_column_int64(pStmt, 1);
        break;

      case OTA_STATE_COOKIE:
        pRet->iCookie = (u32)sqlite3_column_int64(pStmt, 1);
        break;

      case OTA_STATE_OALSZ:
        pRet->iOalSz = (u32)sqlite3_column_int64(pStmt, 1);
        break;

      default:
        rc = SQLITE_CORRUPT;
        break;
    }
  }
  rc2 = sqlite3_finalize(pStmt);
  if( rc==SQLITE_OK ) rc = rc2;

  p->rc = rc;
  return pRet;
}

/*
** Compare strings z1 and z2, returning 0 if they are identical, or non-zero
** otherwise. Either or both argument may be NULL. Two NULL values are
** considered equal, and NULL is considered distinct from all other values.
*/
static int otaStrCompare(const char *z1, const char *z2){
  if( z1==0 && z2==0 ) return 0;
  if( z1==0 || z2==0 ) return 1;
  return (sqlite3_stricmp(z1, z2)!=0);
}

/*
** This function is called as part of sqlite3ota_open() when initializing
** an ota handle in OAL stage. If the ota update has not started (i.e.
** the ota_state table was empty) it is a no-op. Otherwise, it arranges
** things so that the next call to sqlite3ota_step() continues on from
** where the previous ota handle left off.
**
** If an error occurs, an error code and error message are left in the
** ota handle passed as the first argument.
*/
static void otaSetupOal(sqlite3ota *p, OtaState *pState){
  assert( p->rc==SQLITE_OK );
  if( pState->zTbl ){
    OtaObjIter *pIter = &p->objiter;
    int rc = SQLITE_OK;

    while( rc==SQLITE_OK && pIter->zTbl && (pIter->bCleanup 
       || otaStrCompare(pIter->zIdx, pState->zIdx)
       || otaStrCompare(pIter->zTbl, pState->zTbl) 
    )){
      rc = otaObjIterNext(p, pIter);
    }

    if( rc==SQLITE_OK && !pIter->zTbl ){
      rc = SQLITE_ERROR;
      p->zErrmsg = sqlite3_mprintf("ota_state mismatch error");
    }

    if( rc==SQLITE_OK ){
      p->nStep = pState->nRow;
      rc = otaObjIterPrepareAll(p, &p->objiter, p->nStep);
    }

    p->rc = rc;
  }
}

/*
** If there is a "*-oal" file in the file-system corresponding to the
** target database in the file-system, delete it. If an error occurs,
** leave an error code and error message in the ota handle.
*/
static void otaDeleteOalFile(sqlite3ota *p){
  char *zOal = sqlite3_mprintf("%s-oal", p->zTarget);
  assert( p->rc==SQLITE_OK && p->zErrmsg==0 );
  unlink(zOal);
  sqlite3_free(zOal);
}

/*
** Allocate a private ota VFS for the ota handle passed as the only
** argument. This VFS will be used unless the call to sqlite3ota_open()
** specified a URI with a vfs=? option in place of a target database
** file name.
*/
static void otaCreateVfs(sqlite3ota *p){
  int rnd;
  char zRnd[64];

  assert( p->rc==SQLITE_OK );
  sqlite3_randomness(sizeof(int), (void*)&rnd);
  sprintf(zRnd, "ota_vfs_%d", rnd);
  p->rc = sqlite3ota_create_vfs(zRnd, 0);
  if( p->rc==SQLITE_OK ){
    sqlite3_vfs *pVfs = sqlite3_vfs_find(zRnd);
    assert( pVfs );
    p->zVfsName = pVfs->zName;
  }
}

/*
** Destroy the private VFS created for the ota handle passed as the only
** argument by an earlier call to otaCreateVfs().
*/
static void otaDeleteVfs(sqlite3ota *p){
  if( p->zVfsName ){
    sqlite3ota_destroy_vfs(p->zVfsName);
    p->zVfsName = 0;
  }
}

/*
** Open and return a new OTA handle. 
*/
SQLITE_API sqlite3ota *SQLITE_STDCALL sqlite3ota_open(
  const char *zTarget, 
  const char *zOta,
  const char *zState
){
  sqlite3ota *p;
  int nTarget = strlen(zTarget);
  int nOta = strlen(zOta);
  int nState = zState ? strlen(zState) : 0;

  p = (sqlite3ota*)sqlite3_malloc(sizeof(sqlite3ota)+nTarget+1+nOta+1+nState+1);
  if( p ){
    OtaState *pState = 0;

    /* Create the custom VFS. */
    memset(p, 0, sizeof(sqlite3ota));
    otaCreateVfs(p);

    /* Open the target database */
    if( p->rc==SQLITE_OK ){
      p->zTarget = (char*)&p[1];
      memcpy(p->zTarget, zTarget, nTarget+1);
      p->zOta = &p->zTarget[nTarget+1];
      memcpy(p->zOta, zOta, nOta+1);
      if( zState ){
        p->zState = &p->zOta[nOta+1];
        memcpy(p->zState, zState, nState+1);
      }
      otaOpenDatabase(p);
    }

    /* If it has not already been created, create the ota_state table */
    otaMPrintfExec(p, p->dbOta, OTA_CREATE_STATE, p->zStateDb);

    if( p->rc==SQLITE_OK ){
      pState = otaLoadState(p);
      assert( pState || p->rc!=SQLITE_OK );
      if( p->rc==SQLITE_OK ){

        if( pState->eStage==0 ){ 
          otaDeleteOalFile(p);
          p->eStage = OTA_STAGE_OAL;
        }else{
          p->eStage = pState->eStage;
        }
        p->nProgress = pState->nProgress;
        p->iOalSz = pState->iOalSz;
      }
    }
    assert( p->rc!=SQLITE_OK || p->eStage!=0 );

    if( p->rc==SQLITE_OK && p->pTargetFd->pWalFd ){
      if( p->eStage==OTA_STAGE_OAL ){
        p->rc = SQLITE_ERROR;
        p->zErrmsg = sqlite3_mprintf("cannot update wal mode database");
      }else if( p->eStage==OTA_STAGE_MOVE ){
        p->eStage = OTA_STAGE_CKPT;
        p->nStep = 0;
      }
    }

    if( p->rc==SQLITE_OK
     && (p->eStage==OTA_STAGE_OAL || p->eStage==OTA_STAGE_MOVE)
     && pState->eStage!=0 && p->pTargetFd->iCookie!=pState->iCookie
    ){   
      /* At this point (pTargetFd->iCookie) contains the value of the
      ** change-counter cookie (the thing that gets incremented when a 
      ** transaction is committed in rollback mode) currently stored on 
      ** page 1 of the database file. */
      p->rc = SQLITE_BUSY;
      p->zErrmsg = sqlite3_mprintf("database modified during ota update");
    }

    if( p->rc==SQLITE_OK ){
      if( p->eStage==OTA_STAGE_OAL ){

        /* Open transactions both databases. The *-oal file is opened or
        ** created at this point. */
        p->rc = sqlite3_exec(p->dbMain, "BEGIN IMMEDIATE", 0, 0, &p->zErrmsg);
        if( p->rc==SQLITE_OK ){
          p->rc = sqlite3_exec(p->dbOta, "BEGIN IMMEDIATE", 0, 0, &p->zErrmsg);
        }
  
        /* Point the object iterator at the first object */
        if( p->rc==SQLITE_OK ){
          p->rc = otaObjIterFirst(p, &p->objiter);
        }

        /* If the OTA database contains no data_xxx tables, declare the OTA
        ** update finished.  */
        if( p->rc==SQLITE_OK && p->objiter.zTbl==0 ){
          p->rc = SQLITE_DONE;
        }

        if( p->rc==SQLITE_OK ){
          otaSetupOal(p, pState);
        }

      }else if( p->eStage==OTA_STAGE_MOVE ){
        /* no-op */
      }else if( p->eStage==OTA_STAGE_CKPT ){
        otaSetupCheckpoint(p, pState);
      }else if( p->eStage==OTA_STAGE_DONE ){
        p->rc = SQLITE_DONE;
      }else{
        p->rc = SQLITE_CORRUPT;
      }
    }

    otaFreeState(pState);
  }

  return p;
}


/*
** Return the database handle used by pOta.
*/
SQLITE_API sqlite3 *SQLITE_STDCALL sqlite3ota_db(sqlite3ota *pOta, int bOta){
  sqlite3 *db = 0;
  if( pOta ){
    db = (bOta ? pOta->dbOta : pOta->dbMain);
  }
  return db;
}


/*
** If the error code currently stored in the OTA handle is SQLITE_CONSTRAINT,
** then edit any error message string so as to remove all occurrences of
** the pattern "ota_imp_[0-9]*".
*/
static void otaEditErrmsg(sqlite3ota *p){
  if( p->rc==SQLITE_CONSTRAINT && p->zErrmsg ){
    int i;
    int nErrmsg = strlen(p->zErrmsg);
    for(i=0; i<(nErrmsg-8); i++){
      if( memcmp(&p->zErrmsg[i], "ota_imp_", 8)==0 ){
        int nDel = 8;
        while( p->zErrmsg[i+nDel]>='0' && p->zErrmsg[i+nDel]<='9' ) nDel++;
        memmove(&p->zErrmsg[i], &p->zErrmsg[i+nDel], nErrmsg + 1 - i - nDel);
        nErrmsg -= nDel;
      }
    }
  }
}

/*
** Close the OTA handle.
*/
SQLITE_API int SQLITE_STDCALL sqlite3ota_close(sqlite3ota *p, char **pzErrmsg){
  int rc;
  if( p ){

    /* Commit the transaction to the *-oal file. */
    if( p->rc==SQLITE_OK && p->eStage==OTA_STAGE_OAL ){
      p->rc = sqlite3_exec(p->dbMain, "COMMIT", 0, 0, &p->zErrmsg);
    }

    otaSaveState(p, p->eStage);

    if( p->rc==SQLITE_OK && p->eStage==OTA_STAGE_OAL ){
      p->rc = sqlite3_exec(p->dbOta, "COMMIT", 0, 0, &p->zErrmsg);
    }

    /* Close any open statement handles. */
    otaObjIterFinalize(&p->objiter);

    /* Close the open database handle and VFS object. */
    sqlite3_close(p->dbMain);
    sqlite3_close(p->dbOta);
    otaDeleteVfs(p);
    sqlite3_free(p->aBuf);
    sqlite3_free(p->aFrame);

    otaEditErrmsg(p);
    rc = p->rc;
    *pzErrmsg = p->zErrmsg;
    sqlite3_free(p);
  }else{
    rc = SQLITE_NOMEM;
    *pzErrmsg = 0;
  }
  return rc;
}

/*
** Return the total number of key-value operations (inserts, deletes or 
** updates) that have been performed on the target database since the
** current OTA update was started.
*/
SQLITE_API sqlite3_int64 SQLITE_STDCALL sqlite3ota_progress(sqlite3ota *pOta){
  return pOta->nProgress;
}

/**************************************************************************
** Beginning of OTA VFS shim methods. The VFS shim modifies the behaviour
** of a standard VFS in the following ways:
**
** 1. Whenever the first page of a main database file is read or 
**    written, the value of the change-counter cookie is stored in
**    ota_file.iCookie. Similarly, the value of the "write-version"
**    database header field is stored in ota_file.iWriteVer. This ensures
**    that the values are always trustworthy within an open transaction.
**
** 2. Whenever an SQLITE_OPEN_WAL file is opened, the (ota_file.pWalFd)
**    member variable of the associated database file descriptor is set
**    to point to the new file. A mutex protected linked list of all main 
**    db fds opened using a particular OTA VFS is maintained at 
**    ota_vfs.pMain to facilitate this.
**
** 3. Using a new file-control "SQLITE_FCNTL_OTA", a main db ota_file 
**    object can be marked as the target database of an OTA update. This
**    turns on the following extra special behaviour:
**
** 3a. If xAccess() is called to check if there exists a *-wal file 
**     associated with an OTA target database currently in OTA_STAGE_OAL
**     stage (preparing the *-oal file), the following special handling
**     applies:
**
**      * if the *-wal file does exist, return SQLITE_CANTOPEN. An OTA
**        target database may not be in wal mode already.
**
**      * if the *-wal file does not exist, set the output parameter to
**        non-zero (to tell SQLite that it does exist) anyway.
**
**     Then, when xOpen() is called to open the *-wal file associated with
**     the OTA target in OTA_STAGE_OAL stage, instead of opening the *-wal
**     file, the ota vfs opens the corresponding *-oal file instead. 
**
** 3b. The *-shm pages returned by xShmMap() for a target db file in
**     OTA_STAGE_OAL mode are actually stored in heap memory. This is to
**     avoid creating a *-shm file on disk. Additionally, xShmLock() calls
**     are no-ops on target database files in OTA_STAGE_OAL mode. This is
**     because assert() statements in some VFS implementations fail if 
**     xShmLock() is called before xShmMap().
**
** 3c. If an EXCLUSIVE lock is attempted on a target database file in any
**     mode except OTA_STAGE_DONE (all work completed and checkpointed), it 
**     fails with an SQLITE_BUSY error. This is to stop OTA connections
**     from automatically checkpointing a *-wal (or *-oal) file from within
**     sqlite3_close().
**
** 3d. In OTA_STAGE_CAPTURE mode, all xRead() calls on the wal file, and
**     all xWrite() calls on the target database file perform no IO. 
**     Instead the frame and page numbers that would be read and written
**     are recorded. Additionally, successful attempts to obtain exclusive
**     xShmLock() WRITER, CHECKPOINTER and READ0 locks on the target 
**     database file are recorded. xShmLock() calls to unlock the same
**     locks are no-ops (so that once obtained, these locks are never
**     relinquished). Finally, calls to xSync() on the target database
**     file fail with SQLITE_INTERNAL errors.
*/

static void otaUnlockShm(ota_file *p){
  if( p->pOta ){
    int (*xShmLock)(sqlite3_file*,int,int,int) = p->pReal->pMethods->xShmLock;
    int i;
    for(i=0; i<SQLITE_SHM_NLOCK;i++){
      if( (1<<i) & p->pOta->mLock ){
        xShmLock(p->pReal, i, 1, SQLITE_SHM_UNLOCK|SQLITE_SHM_EXCLUSIVE);
      }
    }
    p->pOta->mLock = 0;
  }
}

/*
** Close an ota file.
*/
static int otaVfsClose(sqlite3_file *pFile){
  ota_file *p = (ota_file*)pFile;
  int rc;
  int i;

  /* Free the contents of the apShm[] array. And the array itself. */
  for(i=0; i<p->nShm; i++){
    sqlite3_free(p->apShm[i]);
  }
  sqlite3_free(p->apShm);
  p->apShm = 0;
  sqlite3_free(p->zDel);

  if( p->openFlags & SQLITE_OPEN_MAIN_DB ){
    ota_file **pp;
    sqlite3_mutex_enter(p->pOtaVfs->mutex);
    for(pp=&p->pOtaVfs->pMain; *pp!=p; pp=&((*pp)->pMainNext));
    *pp = p->pMainNext;
    sqlite3_mutex_leave(p->pOtaVfs->mutex);
    otaUnlockShm(p);
    p->pReal->pMethods->xShmUnmap(p->pReal, 0);
  }

  /* Close the underlying file handle */
  rc = p->pReal->pMethods->xClose(p->pReal);
  return rc;
}


/*
** Read and return an unsigned 32-bit big-endian integer from the buffer 
** passed as the only argument.
*/
static u32 otaGetU32(u8 *aBuf){
  return ((u32)aBuf[0] << 24)
       + ((u32)aBuf[1] << 16)
       + ((u32)aBuf[2] <<  8)
       + ((u32)aBuf[3]);
}

/*
** Read data from an otaVfs-file.
*/
static int otaVfsRead(
  sqlite3_file *pFile, 
  void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  ota_file *p = (ota_file*)pFile;
  sqlite3ota *pOta = p->pOta;
  int rc;

  if( pOta && pOta->eStage==OTA_STAGE_CAPTURE ){
    assert( p->openFlags & SQLITE_OPEN_WAL );
    rc = otaCaptureWalRead(p->pOta, iOfst, iAmt);
  }else{
    if( pOta && pOta->eStage==OTA_STAGE_OAL 
     && (p->openFlags & SQLITE_OPEN_WAL) 
     && iOfst>=pOta->iOalSz 
    ){
      rc = SQLITE_OK;
      memset(zBuf, 0, iAmt);
    }else{
      rc = p->pReal->pMethods->xRead(p->pReal, zBuf, iAmt, iOfst);
    }
    if( rc==SQLITE_OK && iOfst==0 && (p->openFlags & SQLITE_OPEN_MAIN_DB) ){
      /* These look like magic numbers. But they are stable, as they are part
       ** of the definition of the SQLite file format, which may not change. */
      u8 *pBuf = (u8*)zBuf;
      p->iCookie = otaGetU32(&pBuf[24]);
      p->iWriteVer = pBuf[19];
    }
  }
  return rc;
}

/*
** Write data to an otaVfs-file.
*/
static int otaVfsWrite(
  sqlite3_file *pFile, 
  const void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  ota_file *p = (ota_file*)pFile;
  sqlite3ota *pOta = p->pOta;
  int rc;

  if( pOta && pOta->eStage==OTA_STAGE_CAPTURE ){
    assert( p->openFlags & SQLITE_OPEN_MAIN_DB );
    rc = otaCaptureDbWrite(p->pOta, iOfst);
  }else{
    if( pOta && pOta->eStage==OTA_STAGE_OAL 
     && (p->openFlags & SQLITE_OPEN_WAL) 
     && iOfst>=pOta->iOalSz
    ){
      pOta->iOalSz = iAmt + iOfst;
    }
    rc = p->pReal->pMethods->xWrite(p->pReal, zBuf, iAmt, iOfst);
    if( rc==SQLITE_OK && iOfst==0 && (p->openFlags & SQLITE_OPEN_MAIN_DB) ){
      /* These look like magic numbers. But they are stable, as they are part
      ** of the definition of the SQLite file format, which may not change. */
      u8 *pBuf = (u8*)zBuf;
      p->iCookie = otaGetU32(&pBuf[24]);
      p->iWriteVer = pBuf[19];
    }
  }
  return rc;
}

/*
** Truncate an otaVfs-file.
*/
static int otaVfsTruncate(sqlite3_file *pFile, sqlite_int64 size){
  ota_file *p = (ota_file*)pFile;
  return p->pReal->pMethods->xTruncate(p->pReal, size);
}

/*
** Sync an otaVfs-file.
*/
static int otaVfsSync(sqlite3_file *pFile, int flags){
  ota_file *p = (ota_file *)pFile;
  if( p->pOta && p->pOta->eStage==OTA_STAGE_CAPTURE ){
    if( p->openFlags & SQLITE_OPEN_MAIN_DB ){
      return SQLITE_INTERNAL;
    }
    return SQLITE_OK;
  }
  return p->pReal->pMethods->xSync(p->pReal, flags);
}

/*
** Return the current file-size of an otaVfs-file.
*/
static int otaVfsFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
  ota_file *p = (ota_file *)pFile;
  return p->pReal->pMethods->xFileSize(p->pReal, pSize);
}

/*
** Lock an otaVfs-file.
*/
static int otaVfsLock(sqlite3_file *pFile, int eLock){
  ota_file *p = (ota_file*)pFile;
  sqlite3ota *pOta = p->pOta;
  int rc = SQLITE_OK;

  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB) );
  if( pOta && eLock==SQLITE_LOCK_EXCLUSIVE && pOta->eStage!=OTA_STAGE_DONE ){
    /* Do not allow EXCLUSIVE locks. Preventing SQLite from taking this 
    ** prevents it from checkpointing the database from sqlite3_close(). */
    rc = SQLITE_BUSY;
  }else{
    rc = p->pReal->pMethods->xLock(p->pReal, eLock);
  }

  return rc;
}

/*
** Unlock an otaVfs-file.
*/
static int otaVfsUnlock(sqlite3_file *pFile, int eLock){
  ota_file *p = (ota_file *)pFile;
  return p->pReal->pMethods->xUnlock(p->pReal, eLock);
}

/*
** Check if another file-handle holds a RESERVED lock on an otaVfs-file.
*/
static int otaVfsCheckReservedLock(sqlite3_file *pFile, int *pResOut){
  ota_file *p = (ota_file *)pFile;
  return p->pReal->pMethods->xCheckReservedLock(p->pReal, pResOut);
}

/*
** File control method. For custom operations on an otaVfs-file.
*/
static int otaVfsFileControl(sqlite3_file *pFile, int op, void *pArg){
  ota_file *p = (ota_file *)pFile;
  int (*xControl)(sqlite3_file*,int,void*) = p->pReal->pMethods->xFileControl;
  int rc;

  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB)
       || p->openFlags & (SQLITE_OPEN_TRANSIENT_DB|SQLITE_OPEN_TEMP_JOURNAL)
  );
  if( op==SQLITE_FCNTL_OTA ){
    sqlite3ota *pOta = (sqlite3ota*)pArg;

    /* First try to find another OTA vfs lower down in the vfs stack. If
    ** one is found, this vfs will operate in pass-through mode. The lower
    ** level vfs will do the special OTA handling.  */
    rc = xControl(p->pReal, op, pArg);

    if( rc==SQLITE_NOTFOUND ){
      /* Now search for a zipvfs instance lower down in the VFS stack. If
      ** one is found, this is an error.  */
      void *dummy = 0;
      rc = xControl(p->pReal, SQLITE_FCNTL_ZIPVFS, &dummy);
      if( rc==SQLITE_OK ){
        rc = SQLITE_ERROR;
        pOta->zErrmsg = sqlite3_mprintf("ota/zipvfs setup error");
      }else if( rc==SQLITE_NOTFOUND ){
        pOta->pTargetFd = p;
        p->pOta = pOta;
        if( p->pWalFd ) p->pWalFd->pOta = pOta;
        rc = SQLITE_OK;
      }
    }
    return rc;
  }

  rc = xControl(p->pReal, op, pArg);
  if( rc==SQLITE_OK && op==SQLITE_FCNTL_VFSNAME ){
    ota_vfs *pOtaVfs = p->pOtaVfs;
    char *zIn = *(char**)pArg;
    char *zOut = sqlite3_mprintf("ota(%s)/%z", pOtaVfs->base.zName, zIn);
    *(char**)pArg = zOut;
    if( zOut==0 ) rc = SQLITE_NOMEM;
  }

  return rc;
}

/*
** Return the sector-size in bytes for an otaVfs-file.
*/
static int otaVfsSectorSize(sqlite3_file *pFile){
  ota_file *p = (ota_file *)pFile;
  return p->pReal->pMethods->xSectorSize(p->pReal);
}

/*
** Return the device characteristic flags supported by an otaVfs-file.
*/
static int otaVfsDeviceCharacteristics(sqlite3_file *pFile){
  ota_file *p = (ota_file *)pFile;
  return p->pReal->pMethods->xDeviceCharacteristics(p->pReal);
}

/*
** Take or release a shared-memory lock.
*/
static int otaVfsShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
  ota_file *p = (ota_file*)pFile;
  sqlite3ota *pOta = p->pOta;
  int rc = SQLITE_OK;

#ifdef SQLITE_AMALGAMATION
    assert( WAL_CKPT_LOCK==1 );
#endif

  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB) );
  if( pOta && (pOta->eStage==OTA_STAGE_OAL || pOta->eStage==OTA_STAGE_MOVE) ){
    /* Magic number 1 is the WAL_CKPT_LOCK lock. Preventing SQLite from
    ** taking this lock also prevents any checkpoints from occurring. 
    ** todo: really, it's not clear why this might occur, as 
    ** wal_autocheckpoint ought to be turned off.  */
    if( ofst==WAL_LOCK_CKPT && n==1 ) rc = SQLITE_BUSY;
  }else{
    int bCapture = 0;
    if( n==1 && (flags & SQLITE_SHM_EXCLUSIVE)
     && pOta && pOta->eStage==OTA_STAGE_CAPTURE
     && (ofst==WAL_LOCK_WRITE || ofst==WAL_LOCK_CKPT || ofst==WAL_LOCK_READ0)
    ){
      bCapture = 1;
    }

    if( bCapture==0 || 0==(flags & SQLITE_SHM_UNLOCK) ){
      rc = p->pReal->pMethods->xShmLock(p->pReal, ofst, n, flags);
      if( bCapture && rc==SQLITE_OK ){
        pOta->mLock |= (1 << ofst);
      }
    }
  }

  return rc;
}

/*
** Obtain a pointer to a mapping of a single 32KiB page of the *-shm file.
*/
static int otaVfsShmMap(
  sqlite3_file *pFile, 
  int iRegion, 
  int szRegion, 
  int isWrite, 
  void volatile **pp
){
  ota_file *p = (ota_file*)pFile;
  int rc = SQLITE_OK;
  int eStage = (p->pOta ? p->pOta->eStage : 0);

  /* If not in OTA_STAGE_OAL, allow this call to pass through. Or, if this
  ** ota is in the OTA_STAGE_OAL state, use heap memory for *-shm space 
  ** instead of a file on disk.  */
  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB) );
  if( eStage==OTA_STAGE_OAL || eStage==OTA_STAGE_MOVE ){
    if( iRegion<=p->nShm ){
      int nByte = (iRegion+1) * sizeof(char*);
      char **apNew = (char**)sqlite3_realloc(p->apShm, nByte);
      if( apNew==0 ){
        rc = SQLITE_NOMEM;
      }else{
        memset(&apNew[p->nShm], 0, sizeof(char*) * (1 + iRegion - p->nShm));







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** Examples:
**
**     test.db-journal    =>   test.nal
**     test.db-wal        =>   test.wal
**     test.db-shm        =>   test.shm
**     test.db-mj7f3319fa =>   test.9fa
*/
static void rbuFileSuffix3(const char *zBase, char *z){
#ifdef SQLITE_ENABLE_8_3_NAMES
#if SQLITE_ENABLE_8_3_NAMES<2
  if( sqlite3_uri_boolean(zBase, "8_3_names", 0) )
#endif
  {
    int i, sz;
    sz = sqlite3Strlen30(z);
    for(i=sz-1; i>0 && z[i]!='/' && z[i]!='.'; i--){}
    if( z[i]=='.' && ALWAYS(sz>i+4) ) memmove(&z[i+1], &z[sz-3], 4);
  }
#endif
}

/*
** Return the current wal-index header checksum for the target database 
** as a 64-bit integer.
**
** The checksum is store in the first page of xShmMap memory as an 8-byte 
** blob starting at byte offset 40.
*/
static i64 rbuShmChecksum(sqlite3rbu *p){
  i64 iRet = 0;
  if( p->rc==SQLITE_OK ){
    sqlite3_file *pDb = p->pTargetFd->pReal;
    u32 volatile *ptr;
    p->rc = pDb->pMethods->xShmMap(pDb, 0, 32*1024, 0, (void volatile**)&ptr);
    if( p->rc==SQLITE_OK ){
      iRet = ((i64)ptr[10] << 32) + ptr[11];
    }
  }
  return iRet;
}

/*
** This function is called as part of initializing or reinitializing an
** incremental checkpoint. 
**
** It populates the sqlite3rbu.aFrame[] array with the set of 
** (wal frame -> db page) copy operations required to checkpoint the 
** current wal file, and obtains the set of shm locks required to safely 
** perform the copy operations directly on the file-system.
**
** If argument pState is not NULL, then the incremental checkpoint is
** being resumed. In this case, if the checksum of the wal-index-header
** following recovery is not the same as the checksum saved in the RbuState
** object, then the rbu handle is set to DONE state. This occurs if some
** other client appends a transaction to the wal file in the middle of
** an incremental checkpoint.
*/
static void rbuSetupCheckpoint(sqlite3rbu *p, RbuState *pState){

  /* If pState is NULL, then the wal file may not have been opened and
  ** recovered. Running a read-statement here to ensure that doing so
  ** does not interfere with the "capture" process below.  */
  if( pState==0 ){
    p->eStage = 0;
    if( p->rc==SQLITE_OK ){
      p->rc = sqlite3_exec(p->dbMain, "SELECT * FROM sqlite_master", 0, 0, 0);
    }
  }

  /* Assuming no error has occurred, run a "restart" checkpoint with the
  ** sqlite3rbu.eStage variable set to CAPTURE. This turns on the following
  ** special behaviour in the rbu VFS:
  **
  **   * If the exclusive shm WRITER or READ0 lock cannot be obtained,
  **     the checkpoint fails with SQLITE_BUSY (normally SQLite would
  **     proceed with running a passive checkpoint instead of failing).
  **
  **   * Attempts to read from the *-wal file or write to the database file
  **     do not perform any IO. Instead, the frame/page combinations that
  **     would be read/written are recorded in the sqlite3rbu.aFrame[]
  **     array.
  **
  **   * Calls to xShmLock(UNLOCK) to release the exclusive shm WRITER, 
  **     READ0 and CHECKPOINT locks taken as part of the checkpoint are
  **     no-ops. These locks will not be released until the connection
  **     is closed.
  **
  **   * Attempting to xSync() the database file causes an SQLITE_INTERNAL 
  **     error.
  **
  ** As a result, unless an error (i.e. OOM or SQLITE_BUSY) occurs, the
  ** checkpoint below fails with SQLITE_INTERNAL, and leaves the aFrame[]
  ** array populated with a set of (frame -> page) mappings. Because the 
  ** WRITER, CHECKPOINT and READ0 locks are still held, it is safe to copy 
  ** data from the wal file into the database file according to the 
  ** contents of aFrame[].
  */
  if( p->rc==SQLITE_OK ){
    int rc2;
    p->eStage = RBU_STAGE_CAPTURE;
    rc2 = sqlite3_exec(p->dbMain, "PRAGMA main.wal_checkpoint=restart", 0, 0,0);
    if( rc2!=SQLITE_INTERNAL ) p->rc = rc2;
  }

  if( p->rc==SQLITE_OK ){
    p->eStage = RBU_STAGE_CKPT;
    p->nStep = (pState ? pState->nRow : 0);
    p->aBuf = rbuMalloc(p, p->pgsz);
    p->iWalCksum = rbuShmChecksum(p);
  }

  if( p->rc==SQLITE_OK && pState && pState->iWalCksum!=p->iWalCksum ){
    p->rc = SQLITE_DONE;
    p->eStage = RBU_STAGE_DONE;
  }
}

/*
** Called when iAmt bytes are read from offset iOff of the wal file while
** the rbu object is in capture mode. Record the frame number of the frame
** being read in the aFrame[] array.
*/
static int rbuCaptureWalRead(sqlite3rbu *pRbu, i64 iOff, int iAmt){
  const u32 mReq = (1<<WAL_LOCK_WRITE)|(1<<WAL_LOCK_CKPT)|(1<<WAL_LOCK_READ0);
  u32 iFrame;

  if( pRbu->mLock!=mReq ){
    pRbu->rc = SQLITE_BUSY;
    return SQLITE_INTERNAL;
  }

  pRbu->pgsz = iAmt;
  if( pRbu->nFrame==pRbu->nFrameAlloc ){
    int nNew = (pRbu->nFrameAlloc ? pRbu->nFrameAlloc : 64) * 2;
    RbuFrame *aNew;
    aNew = (RbuFrame*)sqlite3_realloc(pRbu->aFrame, nNew * sizeof(RbuFrame));
    if( aNew==0 ) return SQLITE_NOMEM;
    pRbu->aFrame = aNew;
    pRbu->nFrameAlloc = nNew;
  }

  iFrame = (u32)((iOff-32) / (i64)(iAmt+24)) + 1;
  if( pRbu->iMaxFrame<iFrame ) pRbu->iMaxFrame = iFrame;
  pRbu->aFrame[pRbu->nFrame].iWalFrame = iFrame;
  pRbu->aFrame[pRbu->nFrame].iDbPage = 0;
  pRbu->nFrame++;
  return SQLITE_OK;
}

/*
** Called when a page of data is written to offset iOff of the database
** file while the rbu handle is in capture mode. Record the page number 
** of the page being written in the aFrame[] array.
*/
static int rbuCaptureDbWrite(sqlite3rbu *pRbu, i64 iOff){
  pRbu->aFrame[pRbu->nFrame-1].iDbPage = (u32)(iOff / pRbu->pgsz) + 1;
  return SQLITE_OK;
}

/*
** This is called as part of an incremental checkpoint operation. Copy
** a single frame of data from the wal file into the database file, as
** indicated by the RbuFrame object.
*/
static void rbuCheckpointFrame(sqlite3rbu *p, RbuFrame *pFrame){
  sqlite3_file *pWal = p->pTargetFd->pWalFd->pReal;
  sqlite3_file *pDb = p->pTargetFd->pReal;
  i64 iOff;

  assert( p->rc==SQLITE_OK );
  iOff = (i64)(pFrame->iWalFrame-1) * (p->pgsz + 24) + 32 + 24;
  p->rc = pWal->pMethods->xRead(pWal, p->aBuf, p->pgsz, iOff);
  if( p->rc ) return;

  iOff = (i64)(pFrame->iDbPage-1) * p->pgsz;
  p->rc = pDb->pMethods->xWrite(pDb, p->aBuf, p->pgsz, iOff);
}


/*
** Take an EXCLUSIVE lock on the database file.
*/
static void rbuLockDatabase(sqlite3rbu *p){
  sqlite3_file *pReal = p->pTargetFd->pReal;
  assert( p->rc==SQLITE_OK );
  p->rc = pReal->pMethods->xLock(pReal, SQLITE_LOCK_SHARED);
  if( p->rc==SQLITE_OK ){
    p->rc = pReal->pMethods->xLock(pReal, SQLITE_LOCK_EXCLUSIVE);
  }
}

/*
** The RBU handle is currently in RBU_STAGE_OAL state, with a SHARED lock
** on the database file. This proc moves the *-oal file to the *-wal path,
** then reopens the database file (this time in vanilla, non-oal, WAL mode).
** If an error occurs, leave an error code and error message in the rbu 
** handle.
*/
static void rbuMoveOalFile(sqlite3rbu *p){
  const char *zBase = sqlite3_db_filename(p->dbMain, "main");

  char *zWal = sqlite3_mprintf("%s-wal", zBase);
  char *zOal = sqlite3_mprintf("%s-oal", zBase);

  assert( p->eStage==RBU_STAGE_MOVE );
  assert( p->rc==SQLITE_OK && p->zErrmsg==0 );
  if( zWal==0 || zOal==0 ){
    p->rc = SQLITE_NOMEM;
  }else{
    /* Move the *-oal file to *-wal. At this point connection p->db is
    ** holding a SHARED lock on the target database file (because it is
    ** in WAL mode). So no other connection may be writing the db. 
    **
    ** In order to ensure that there are no database readers, an EXCLUSIVE
    ** lock is obtained here before the *-oal is moved to *-wal.
    */
    rbuLockDatabase(p);
    if( p->rc==SQLITE_OK ){
      rbuFileSuffix3(zBase, zWal);
      rbuFileSuffix3(zBase, zOal);

      /* Re-open the databases. */
      rbuObjIterFinalize(&p->objiter);
      sqlite3_close(p->dbMain);
      sqlite3_close(p->dbRbu);
      p->rc = rename(zOal, zWal) ? SQLITE_IOERR : SQLITE_OK;
      if( p->rc==SQLITE_OK ){
        p->dbMain = 0;
        p->dbRbu = 0;
        rbuOpenDatabase(p);
        rbuSetupCheckpoint(p, 0);
      }
    }
  }

  sqlite3_free(zWal);
  sqlite3_free(zOal);
}

/*
** The SELECT statement iterating through the keys for the current object
** (p->objiter.pSelect) currently points to a valid row. This function
** determines the type of operation requested by this row and returns
** one of the following values to indicate the result:
**
**     * RBU_INSERT
**     * RBU_DELETE
**     * RBU_IDX_DELETE
**     * RBU_UPDATE
**
** If RBU_UPDATE is returned, then output variable *pzMask is set to
** point to the text value indicating the columns to update.
**
** If the rbu_control field contains an invalid value, an error code and
** message are left in the RBU handle and zero returned.
*/
static int rbuStepType(sqlite3rbu *p, const char **pzMask){
  int iCol = p->objiter.nCol;     /* Index of rbu_control column */
  int res = 0;                    /* Return value */

  switch( sqlite3_column_type(p->objiter.pSelect, iCol) ){
    case SQLITE_INTEGER: {
      int iVal = sqlite3_column_int(p->objiter.pSelect, iCol);
      if( iVal==0 ){
        res = RBU_INSERT;
      }else if( iVal==1 ){
        res = RBU_DELETE;
      }else if( iVal==2 ){
        res = RBU_IDX_DELETE;
      }else if( iVal==3 ){
        res = RBU_IDX_INSERT;
      }
      break;
    }

    case SQLITE_TEXT: {
      const unsigned char *z = sqlite3_column_text(p->objiter.pSelect, iCol);
      if( z==0 ){
        p->rc = SQLITE_NOMEM;
      }else{
        *pzMask = (const char*)z;
      }
      res = RBU_UPDATE;

      break;
    }

    default:
      break;
  }

  if( res==0 ){
    rbuBadControlError(p);
  }
  return res;
}

#ifdef SQLITE_DEBUG
/*
** Assert that column iCol of statement pStmt is named zName.
*/
static void assertColumnName(sqlite3_stmt *pStmt, int iCol, const char *zName){
  const char *zCol = sqlite3_column_name(pStmt, iCol);
  assert( 0==sqlite3_stricmp(zName, zCol) );
}
#else
# define assertColumnName(x,y,z)
#endif

/*
** This function does the work for an sqlite3rbu_step() call.
**
** The object-iterator (p->objiter) currently points to a valid object,
** and the input cursor (p->objiter.pSelect) currently points to a valid
** input row. Perform whatever processing is required and return.
**
** If no  error occurs, SQLITE_OK is returned. Otherwise, an error code
** and message is left in the RBU handle and a copy of the error code
** returned.
*/
static int rbuStep(sqlite3rbu *p){
  RbuObjIter *pIter = &p->objiter;
  const char *zMask = 0;
  int i;
  int eType = rbuStepType(p, &zMask);

  if( eType ){
    assert( eType!=RBU_UPDATE || pIter->zIdx==0 );

    if( pIter->zIdx==0 && eType==RBU_IDX_DELETE ){
      rbuBadControlError(p);
    }
    else if( 
        eType==RBU_INSERT 
     || eType==RBU_DELETE
     || eType==RBU_IDX_DELETE 
     || eType==RBU_IDX_INSERT
    ){
      sqlite3_value *pVal;
      sqlite3_stmt *pWriter;

      assert( eType!=RBU_UPDATE );
      assert( eType!=RBU_DELETE || pIter->zIdx==0 );

      if( eType==RBU_IDX_DELETE || eType==RBU_DELETE ){
        pWriter = pIter->pDelete;
      }else{
        pWriter = pIter->pInsert;
      }

      for(i=0; i<pIter->nCol; i++){
        /* If this is an INSERT into a table b-tree and the table has an
        ** explicit INTEGER PRIMARY KEY, check that this is not an attempt
        ** to write a NULL into the IPK column. That is not permitted.  */
        if( eType==RBU_INSERT 
         && pIter->zIdx==0 && pIter->eType==RBU_PK_IPK && pIter->abTblPk[i] 
         && sqlite3_column_type(pIter->pSelect, i)==SQLITE_NULL
        ){
          p->rc = SQLITE_MISMATCH;
          p->zErrmsg = sqlite3_mprintf("datatype mismatch");
          goto step_out;
        }

        if( eType==RBU_DELETE && pIter->abTblPk[i]==0 ){
          continue;
        }

        pVal = sqlite3_column_value(pIter->pSelect, i);
        p->rc = sqlite3_bind_value(pWriter, i+1, pVal);
        if( p->rc ) goto step_out;
      }
      if( pIter->zIdx==0
       && (pIter->eType==RBU_PK_VTAB || pIter->eType==RBU_PK_NONE) 
      ){
        /* For a virtual table, or a table with no primary key, the 
        ** SELECT statement is:
        **
        **   SELECT <cols>, rbu_control, rbu_rowid FROM ....
        **
        ** Hence column_value(pIter->nCol+1).
        */
        assertColumnName(pIter->pSelect, pIter->nCol+1, "rbu_rowid");
        pVal = sqlite3_column_value(pIter->pSelect, pIter->nCol+1);
        p->rc = sqlite3_bind_value(pWriter, pIter->nCol+1, pVal);
      }
      if( p->rc==SQLITE_OK ){
        sqlite3_step(pWriter);
        p->rc = resetAndCollectError(pWriter, &p->zErrmsg);
      }
    }else{
      sqlite3_value *pVal;
      sqlite3_stmt *pUpdate = 0;
      assert( eType==RBU_UPDATE );
      rbuGetUpdateStmt(p, pIter, zMask, &pUpdate);
      if( pUpdate ){
        for(i=0; p->rc==SQLITE_OK && i<pIter->nCol; i++){
          char c = zMask[pIter->aiSrcOrder[i]];
          pVal = sqlite3_column_value(pIter->pSelect, i);
          if( pIter->abTblPk[i] || c=='x' || c=='d' ){
            p->rc = sqlite3_bind_value(pUpdate, i+1, pVal);
          }
        }
        if( p->rc==SQLITE_OK 
         && (pIter->eType==RBU_PK_VTAB || pIter->eType==RBU_PK_NONE) 
        ){
          /* Bind the rbu_rowid value to column _rowid_ */
          assertColumnName(pIter->pSelect, pIter->nCol+1, "rbu_rowid");
          pVal = sqlite3_column_value(pIter->pSelect, pIter->nCol+1);
          p->rc = sqlite3_bind_value(pUpdate, pIter->nCol+1, pVal);
        }
        if( p->rc==SQLITE_OK ){
          sqlite3_step(pUpdate);
          p->rc = resetAndCollectError(pUpdate, &p->zErrmsg);
        }
      }
    }
  }

 step_out:
  return p->rc;
}

/*
** Increment the schema cookie of the main database opened by p->dbMain.
*/
static void rbuIncrSchemaCookie(sqlite3rbu *p){
  if( p->rc==SQLITE_OK ){
    int iCookie = 1000000;
    sqlite3_stmt *pStmt;

    p->rc = prepareAndCollectError(p->dbMain, &pStmt, &p->zErrmsg, 
        "PRAGMA schema_version"
    );
    if( p->rc==SQLITE_OK ){
      /* Coverage: it may be that this sqlite3_step() cannot fail. There
      ** is already a transaction open, so the prepared statement cannot
      ** throw an SQLITE_SCHEMA exception. The only database page the
      ** statement reads is page 1, which is guaranteed to be in the cache.
      ** And no memory allocations are required.  */
      if( SQLITE_ROW==sqlite3_step(pStmt) ){
        iCookie = sqlite3_column_int(pStmt, 0);
      }
      rbuFinalize(p, pStmt);
    }
    if( p->rc==SQLITE_OK ){
      rbuMPrintfExec(p, p->dbMain, "PRAGMA schema_version = %d", iCookie+1);
    }
  }
}

/*
** Update the contents of the rbu_state table within the rbu database. The
** value stored in the RBU_STATE_STAGE column is eStage. All other values
** are determined by inspecting the rbu handle passed as the first argument.
*/
static void rbuSaveState(sqlite3rbu *p, int eStage){
  if( p->rc==SQLITE_OK || p->rc==SQLITE_DONE ){
    sqlite3_stmt *pInsert = 0;
    int rc;

    assert( p->zErrmsg==0 );
    rc = prepareFreeAndCollectError(p->dbRbu, &pInsert, &p->zErrmsg, 
        sqlite3_mprintf(
          "INSERT OR REPLACE INTO %s.rbu_state(k, v) VALUES "
          "(%d, %d), "
          "(%d, %Q), "
          "(%d, %Q), "
          "(%d, %d), "
          "(%d, %d), "
          "(%d, %lld), "
          "(%d, %lld), "
          "(%d, %lld) ",
          p->zStateDb,
          RBU_STATE_STAGE, eStage,
          RBU_STATE_TBL, p->objiter.zTbl, 
          RBU_STATE_IDX, p->objiter.zIdx, 
          RBU_STATE_ROW, p->nStep, 
          RBU_STATE_PROGRESS, p->nProgress,
          RBU_STATE_CKPT, p->iWalCksum,
          RBU_STATE_COOKIE, (i64)p->pTargetFd->iCookie,
          RBU_STATE_OALSZ, p->iOalSz
      )
    );
    assert( pInsert==0 || rc==SQLITE_OK );

    if( rc==SQLITE_OK ){
      sqlite3_step(pInsert);
      rc = sqlite3_finalize(pInsert);
    }
    if( rc!=SQLITE_OK ) p->rc = rc;
  }
}


/*
** Step the RBU object.
*/
SQLITE_API int SQLITE_STDCALL sqlite3rbu_step(sqlite3rbu *p){
  if( p ){
    switch( p->eStage ){
      case RBU_STAGE_OAL: {
        RbuObjIter *pIter = &p->objiter;
        while( p->rc==SQLITE_OK && pIter->zTbl ){

          if( pIter->bCleanup ){
            /* Clean up the rbu_tmp_xxx table for the previous table. It 
            ** cannot be dropped as there are currently active SQL statements.
            ** But the contents can be deleted.  */
            if( pIter->abIndexed ){
              rbuMPrintfExec(p, p->dbRbu, 
                  "DELETE FROM %s.'rbu_tmp_%q'", p->zStateDb, pIter->zTbl
              );
            }
          }else{
            rbuObjIterPrepareAll(p, pIter, 0);

            /* Advance to the next row to process. */
            if( p->rc==SQLITE_OK ){
              int rc = sqlite3_step(pIter->pSelect);
              if( rc==SQLITE_ROW ){
                p->nProgress++;
                p->nStep++;
                return rbuStep(p);
              }
              p->rc = sqlite3_reset(pIter->pSelect);
              p->nStep = 0;
            }
          }

          rbuObjIterNext(p, pIter);
        }

        if( p->rc==SQLITE_OK ){
          assert( pIter->zTbl==0 );
          rbuSaveState(p, RBU_STAGE_MOVE);
          rbuIncrSchemaCookie(p);
          if( p->rc==SQLITE_OK ){
            p->rc = sqlite3_exec(p->dbMain, "COMMIT", 0, 0, &p->zErrmsg);
          }
          if( p->rc==SQLITE_OK ){
            p->rc = sqlite3_exec(p->dbRbu, "COMMIT", 0, 0, &p->zErrmsg);
          }
          p->eStage = RBU_STAGE_MOVE;
        }
        break;
      }

      case RBU_STAGE_MOVE: {
        if( p->rc==SQLITE_OK ){
          rbuMoveOalFile(p);
          p->nProgress++;
        }
        break;
      }

      case RBU_STAGE_CKPT: {
        if( p->rc==SQLITE_OK ){
          if( p->nStep>=p->nFrame ){
            sqlite3_file *pDb = p->pTargetFd->pReal;
  
            /* Sync the db file */
            p->rc = pDb->pMethods->xSync(pDb, SQLITE_SYNC_NORMAL);
  
            /* Update nBackfill */
            if( p->rc==SQLITE_OK ){
              void volatile *ptr;
              p->rc = pDb->pMethods->xShmMap(pDb, 0, 32*1024, 0, &ptr);
              if( p->rc==SQLITE_OK ){
                ((u32 volatile*)ptr)[24] = p->iMaxFrame;
              }
            }
  
            if( p->rc==SQLITE_OK ){
              p->eStage = RBU_STAGE_DONE;
              p->rc = SQLITE_DONE;
            }
          }else{
            RbuFrame *pFrame = &p->aFrame[p->nStep];
            rbuCheckpointFrame(p, pFrame);
            p->nStep++;
          }
          p->nProgress++;
        }
        break;
      }

      default:
        break;
    }
    return p->rc;
  }else{
    return SQLITE_NOMEM;
  }
}

/*
** Free an RbuState object allocated by rbuLoadState().
*/
static void rbuFreeState(RbuState *p){
  if( p ){
    sqlite3_free(p->zTbl);
    sqlite3_free(p->zIdx);
    sqlite3_free(p);
  }
}

/*
** Allocate an RbuState object and load the contents of the rbu_state 
** table into it. Return a pointer to the new object. It is the 
** responsibility of the caller to eventually free the object using
** sqlite3_free().
**
** If an error occurs, leave an error code and message in the rbu handle
** and return NULL.
*/
static RbuState *rbuLoadState(sqlite3rbu *p){
  RbuState *pRet = 0;
  sqlite3_stmt *pStmt = 0;
  int rc;
  int rc2;

  pRet = (RbuState*)rbuMalloc(p, sizeof(RbuState));
  if( pRet==0 ) return 0;

  rc = prepareFreeAndCollectError(p->dbRbu, &pStmt, &p->zErrmsg, 
      sqlite3_mprintf("SELECT k, v FROM %s.rbu_state", p->zStateDb)
  );
  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
    switch( sqlite3_column_int(pStmt, 0) ){
      case RBU_STATE_STAGE:
        pRet->eStage = sqlite3_column_int(pStmt, 1);
        if( pRet->eStage!=RBU_STAGE_OAL
         && pRet->eStage!=RBU_STAGE_MOVE
         && pRet->eStage!=RBU_STAGE_CKPT
        ){
          p->rc = SQLITE_CORRUPT;
        }
        break;

      case RBU_STATE_TBL:
        pRet->zTbl = rbuStrndup((char*)sqlite3_column_text(pStmt, 1), &rc);
        break;

      case RBU_STATE_IDX:
        pRet->zIdx = rbuStrndup((char*)sqlite3_column_text(pStmt, 1), &rc);
        break;

      case RBU_STATE_ROW:
        pRet->nRow = sqlite3_column_int(pStmt, 1);
        break;

      case RBU_STATE_PROGRESS:
        pRet->nProgress = sqlite3_column_int64(pStmt, 1);
        break;

      case RBU_STATE_CKPT:
        pRet->iWalCksum = sqlite3_column_int64(pStmt, 1);
        break;

      case RBU_STATE_COOKIE:
        pRet->iCookie = (u32)sqlite3_column_int64(pStmt, 1);
        break;

      case RBU_STATE_OALSZ:
        pRet->iOalSz = (u32)sqlite3_column_int64(pStmt, 1);
        break;

      default:
        rc = SQLITE_CORRUPT;
        break;
    }
  }
  rc2 = sqlite3_finalize(pStmt);
  if( rc==SQLITE_OK ) rc = rc2;

  p->rc = rc;
  return pRet;
}

/*
** Compare strings z1 and z2, returning 0 if they are identical, or non-zero
** otherwise. Either or both argument may be NULL. Two NULL values are
** considered equal, and NULL is considered distinct from all other values.
*/
static int rbuStrCompare(const char *z1, const char *z2){
  if( z1==0 && z2==0 ) return 0;
  if( z1==0 || z2==0 ) return 1;
  return (sqlite3_stricmp(z1, z2)!=0);
}

/*
** This function is called as part of sqlite3rbu_open() when initializing
** an rbu handle in OAL stage. If the rbu update has not started (i.e.
** the rbu_state table was empty) it is a no-op. Otherwise, it arranges
** things so that the next call to sqlite3rbu_step() continues on from
** where the previous rbu handle left off.
**
** If an error occurs, an error code and error message are left in the
** rbu handle passed as the first argument.
*/
static void rbuSetupOal(sqlite3rbu *p, RbuState *pState){
  assert( p->rc==SQLITE_OK );
  if( pState->zTbl ){
    RbuObjIter *pIter = &p->objiter;
    int rc = SQLITE_OK;

    while( rc==SQLITE_OK && pIter->zTbl && (pIter->bCleanup 
       || rbuStrCompare(pIter->zIdx, pState->zIdx)
       || rbuStrCompare(pIter->zTbl, pState->zTbl) 
    )){
      rc = rbuObjIterNext(p, pIter);
    }

    if( rc==SQLITE_OK && !pIter->zTbl ){
      rc = SQLITE_ERROR;
      p->zErrmsg = sqlite3_mprintf("rbu_state mismatch error");
    }

    if( rc==SQLITE_OK ){
      p->nStep = pState->nRow;
      rc = rbuObjIterPrepareAll(p, &p->objiter, p->nStep);
    }

    p->rc = rc;
  }
}

/*
** If there is a "*-oal" file in the file-system corresponding to the
** target database in the file-system, delete it. If an error occurs,
** leave an error code and error message in the rbu handle.
*/
static void rbuDeleteOalFile(sqlite3rbu *p){
  char *zOal = sqlite3_mprintf("%s-oal", p->zTarget);
  assert( p->rc==SQLITE_OK && p->zErrmsg==0 );
  unlink(zOal);
  sqlite3_free(zOal);
}

/*
** Allocate a private rbu VFS for the rbu handle passed as the only
** argument. This VFS will be used unless the call to sqlite3rbu_open()
** specified a URI with a vfs=? option in place of a target database
** file name.
*/
static void rbuCreateVfs(sqlite3rbu *p){
  int rnd;
  char zRnd[64];

  assert( p->rc==SQLITE_OK );
  sqlite3_randomness(sizeof(int), (void*)&rnd);
  sprintf(zRnd, "rbu_vfs_%d", rnd);
  p->rc = sqlite3rbu_create_vfs(zRnd, 0);
  if( p->rc==SQLITE_OK ){
    sqlite3_vfs *pVfs = sqlite3_vfs_find(zRnd);
    assert( pVfs );
    p->zVfsName = pVfs->zName;
  }
}

/*
** Destroy the private VFS created for the rbu handle passed as the only
** argument by an earlier call to rbuCreateVfs().
*/
static void rbuDeleteVfs(sqlite3rbu *p){
  if( p->zVfsName ){
    sqlite3rbu_destroy_vfs(p->zVfsName);
    p->zVfsName = 0;
  }
}

/*
** Open and return a new RBU handle. 
*/
SQLITE_API sqlite3rbu *SQLITE_STDCALL sqlite3rbu_open(
  const char *zTarget, 
  const char *zRbu,
  const char *zState
){
  sqlite3rbu *p;
  int nTarget = strlen(zTarget);
  int nRbu = strlen(zRbu);
  int nState = zState ? strlen(zState) : 0;

  p = (sqlite3rbu*)sqlite3_malloc(sizeof(sqlite3rbu)+nTarget+1+nRbu+1+nState+1);
  if( p ){
    RbuState *pState = 0;

    /* Create the custom VFS. */
    memset(p, 0, sizeof(sqlite3rbu));
    rbuCreateVfs(p);

    /* Open the target database */
    if( p->rc==SQLITE_OK ){
      p->zTarget = (char*)&p[1];
      memcpy(p->zTarget, zTarget, nTarget+1);
      p->zRbu = &p->zTarget[nTarget+1];
      memcpy(p->zRbu, zRbu, nRbu+1);
      if( zState ){
        p->zState = &p->zRbu[nRbu+1];
        memcpy(p->zState, zState, nState+1);
      }
      rbuOpenDatabase(p);
    }

    /* If it has not already been created, create the rbu_state table */
    rbuMPrintfExec(p, p->dbRbu, RBU_CREATE_STATE, p->zStateDb);

    if( p->rc==SQLITE_OK ){
      pState = rbuLoadState(p);
      assert( pState || p->rc!=SQLITE_OK );
      if( p->rc==SQLITE_OK ){

        if( pState->eStage==0 ){ 
          rbuDeleteOalFile(p);
          p->eStage = RBU_STAGE_OAL;
        }else{
          p->eStage = pState->eStage;
        }
        p->nProgress = pState->nProgress;
        p->iOalSz = pState->iOalSz;
      }
    }
    assert( p->rc!=SQLITE_OK || p->eStage!=0 );

    if( p->rc==SQLITE_OK && p->pTargetFd->pWalFd ){
      if( p->eStage==RBU_STAGE_OAL ){
        p->rc = SQLITE_ERROR;
        p->zErrmsg = sqlite3_mprintf("cannot update wal mode database");
      }else if( p->eStage==RBU_STAGE_MOVE ){
        p->eStage = RBU_STAGE_CKPT;
        p->nStep = 0;
      }
    }

    if( p->rc==SQLITE_OK
     && (p->eStage==RBU_STAGE_OAL || p->eStage==RBU_STAGE_MOVE)
     && pState->eStage!=0 && p->pTargetFd->iCookie!=pState->iCookie
    ){   
      /* At this point (pTargetFd->iCookie) contains the value of the
      ** change-counter cookie (the thing that gets incremented when a 
      ** transaction is committed in rollback mode) currently stored on 
      ** page 1 of the database file. */
      p->rc = SQLITE_BUSY;
      p->zErrmsg = sqlite3_mprintf("database modified during rbu update");
    }

    if( p->rc==SQLITE_OK ){
      if( p->eStage==RBU_STAGE_OAL ){

        /* Open transactions both databases. The *-oal file is opened or
        ** created at this point. */
        p->rc = sqlite3_exec(p->dbMain, "BEGIN IMMEDIATE", 0, 0, &p->zErrmsg);
        if( p->rc==SQLITE_OK ){
          p->rc = sqlite3_exec(p->dbRbu, "BEGIN IMMEDIATE", 0, 0, &p->zErrmsg);
        }
  
        /* Point the object iterator at the first object */
        if( p->rc==SQLITE_OK ){
          p->rc = rbuObjIterFirst(p, &p->objiter);
        }

        /* If the RBU database contains no data_xxx tables, declare the RBU
        ** update finished.  */
        if( p->rc==SQLITE_OK && p->objiter.zTbl==0 ){
          p->rc = SQLITE_DONE;
        }

        if( p->rc==SQLITE_OK ){
          rbuSetupOal(p, pState);
        }

      }else if( p->eStage==RBU_STAGE_MOVE ){
        /* no-op */
      }else if( p->eStage==RBU_STAGE_CKPT ){
        rbuSetupCheckpoint(p, pState);
      }else if( p->eStage==RBU_STAGE_DONE ){
        p->rc = SQLITE_DONE;
      }else{
        p->rc = SQLITE_CORRUPT;
      }
    }

    rbuFreeState(pState);
  }

  return p;
}


/*
** Return the database handle used by pRbu.
*/
SQLITE_API sqlite3 *SQLITE_STDCALL sqlite3rbu_db(sqlite3rbu *pRbu, int bRbu){
  sqlite3 *db = 0;
  if( pRbu ){
    db = (bRbu ? pRbu->dbRbu : pRbu->dbMain);
  }
  return db;
}


/*
** If the error code currently stored in the RBU handle is SQLITE_CONSTRAINT,
** then edit any error message string so as to remove all occurrences of
** the pattern "rbu_imp_[0-9]*".
*/
static void rbuEditErrmsg(sqlite3rbu *p){
  if( p->rc==SQLITE_CONSTRAINT && p->zErrmsg ){
    int i;
    int nErrmsg = strlen(p->zErrmsg);
    for(i=0; i<(nErrmsg-8); i++){
      if( memcmp(&p->zErrmsg[i], "rbu_imp_", 8)==0 ){
        int nDel = 8;
        while( p->zErrmsg[i+nDel]>='0' && p->zErrmsg[i+nDel]<='9' ) nDel++;
        memmove(&p->zErrmsg[i], &p->zErrmsg[i+nDel], nErrmsg + 1 - i - nDel);
        nErrmsg -= nDel;
      }
    }
  }
}

/*
** Close the RBU handle.
*/
SQLITE_API int SQLITE_STDCALL sqlite3rbu_close(sqlite3rbu *p, char **pzErrmsg){
  int rc;
  if( p ){

    /* Commit the transaction to the *-oal file. */
    if( p->rc==SQLITE_OK && p->eStage==RBU_STAGE_OAL ){
      p->rc = sqlite3_exec(p->dbMain, "COMMIT", 0, 0, &p->zErrmsg);
    }

    rbuSaveState(p, p->eStage);

    if( p->rc==SQLITE_OK && p->eStage==RBU_STAGE_OAL ){
      p->rc = sqlite3_exec(p->dbRbu, "COMMIT", 0, 0, &p->zErrmsg);
    }

    /* Close any open statement handles. */
    rbuObjIterFinalize(&p->objiter);

    /* Close the open database handle and VFS object. */
    sqlite3_close(p->dbMain);
    sqlite3_close(p->dbRbu);
    rbuDeleteVfs(p);
    sqlite3_free(p->aBuf);
    sqlite3_free(p->aFrame);

    rbuEditErrmsg(p);
    rc = p->rc;
    *pzErrmsg = p->zErrmsg;
    sqlite3_free(p);
  }else{
    rc = SQLITE_NOMEM;
    *pzErrmsg = 0;
  }
  return rc;
}

/*
** Return the total number of key-value operations (inserts, deletes or 
** updates) that have been performed on the target database since the
** current RBU update was started.
*/
SQLITE_API sqlite3_int64 SQLITE_STDCALL sqlite3rbu_progress(sqlite3rbu *pRbu){
  return pRbu->nProgress;
}

/**************************************************************************
** Beginning of RBU VFS shim methods. The VFS shim modifies the behaviour
** of a standard VFS in the following ways:
**
** 1. Whenever the first page of a main database file is read or 
**    written, the value of the change-counter cookie is stored in
**    rbu_file.iCookie. Similarly, the value of the "write-version"
**    database header field is stored in rbu_file.iWriteVer. This ensures
**    that the values are always trustworthy within an open transaction.
**
** 2. Whenever an SQLITE_OPEN_WAL file is opened, the (rbu_file.pWalFd)
**    member variable of the associated database file descriptor is set
**    to point to the new file. A mutex protected linked list of all main 
**    db fds opened using a particular RBU VFS is maintained at 
**    rbu_vfs.pMain to facilitate this.
**
** 3. Using a new file-control "SQLITE_FCNTL_RBU", a main db rbu_file 
**    object can be marked as the target database of an RBU update. This
**    turns on the following extra special behaviour:
**
** 3a. If xAccess() is called to check if there exists a *-wal file 
**     associated with an RBU target database currently in RBU_STAGE_OAL
**     stage (preparing the *-oal file), the following special handling
**     applies:
**
**      * if the *-wal file does exist, return SQLITE_CANTOPEN. An RBU
**        target database may not be in wal mode already.
**
**      * if the *-wal file does not exist, set the output parameter to
**        non-zero (to tell SQLite that it does exist) anyway.
**
**     Then, when xOpen() is called to open the *-wal file associated with
**     the RBU target in RBU_STAGE_OAL stage, instead of opening the *-wal
**     file, the rbu vfs opens the corresponding *-oal file instead. 
**
** 3b. The *-shm pages returned by xShmMap() for a target db file in
**     RBU_STAGE_OAL mode are actually stored in heap memory. This is to
**     avoid creating a *-shm file on disk. Additionally, xShmLock() calls
**     are no-ops on target database files in RBU_STAGE_OAL mode. This is
**     because assert() statements in some VFS implementations fail if 
**     xShmLock() is called before xShmMap().
**
** 3c. If an EXCLUSIVE lock is attempted on a target database file in any
**     mode except RBU_STAGE_DONE (all work completed and checkpointed), it 
**     fails with an SQLITE_BUSY error. This is to stop RBU connections
**     from automatically checkpointing a *-wal (or *-oal) file from within
**     sqlite3_close().
**
** 3d. In RBU_STAGE_CAPTURE mode, all xRead() calls on the wal file, and
**     all xWrite() calls on the target database file perform no IO. 
**     Instead the frame and page numbers that would be read and written
**     are recorded. Additionally, successful attempts to obtain exclusive
**     xShmLock() WRITER, CHECKPOINTER and READ0 locks on the target 
**     database file are recorded. xShmLock() calls to unlock the same
**     locks are no-ops (so that once obtained, these locks are never
**     relinquished). Finally, calls to xSync() on the target database
**     file fail with SQLITE_INTERNAL errors.
*/

static void rbuUnlockShm(rbu_file *p){
  if( p->pRbu ){
    int (*xShmLock)(sqlite3_file*,int,int,int) = p->pReal->pMethods->xShmLock;
    int i;
    for(i=0; i<SQLITE_SHM_NLOCK;i++){
      if( (1<<i) & p->pRbu->mLock ){
        xShmLock(p->pReal, i, 1, SQLITE_SHM_UNLOCK|SQLITE_SHM_EXCLUSIVE);
      }
    }
    p->pRbu->mLock = 0;
  }
}

/*
** Close an rbu file.
*/
static int rbuVfsClose(sqlite3_file *pFile){
  rbu_file *p = (rbu_file*)pFile;
  int rc;
  int i;

  /* Free the contents of the apShm[] array. And the array itself. */
  for(i=0; i<p->nShm; i++){
    sqlite3_free(p->apShm[i]);
  }
  sqlite3_free(p->apShm);
  p->apShm = 0;
  sqlite3_free(p->zDel);

  if( p->openFlags & SQLITE_OPEN_MAIN_DB ){
    rbu_file **pp;
    sqlite3_mutex_enter(p->pRbuVfs->mutex);
    for(pp=&p->pRbuVfs->pMain; *pp!=p; pp=&((*pp)->pMainNext));
    *pp = p->pMainNext;
    sqlite3_mutex_leave(p->pRbuVfs->mutex);
    rbuUnlockShm(p);
    p->pReal->pMethods->xShmUnmap(p->pReal, 0);
  }

  /* Close the underlying file handle */
  rc = p->pReal->pMethods->xClose(p->pReal);
  return rc;
}


/*
** Read and return an unsigned 32-bit big-endian integer from the buffer 
** passed as the only argument.
*/
static u32 rbuGetU32(u8 *aBuf){
  return ((u32)aBuf[0] << 24)
       + ((u32)aBuf[1] << 16)
       + ((u32)aBuf[2] <<  8)
       + ((u32)aBuf[3]);
}

/*
** Read data from an rbuVfs-file.
*/
static int rbuVfsRead(
  sqlite3_file *pFile, 
  void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  rbu_file *p = (rbu_file*)pFile;
  sqlite3rbu *pRbu = p->pRbu;
  int rc;

  if( pRbu && pRbu->eStage==RBU_STAGE_CAPTURE ){
    assert( p->openFlags & SQLITE_OPEN_WAL );
    rc = rbuCaptureWalRead(p->pRbu, iOfst, iAmt);
  }else{
    if( pRbu && pRbu->eStage==RBU_STAGE_OAL 
     && (p->openFlags & SQLITE_OPEN_WAL) 
     && iOfst>=pRbu->iOalSz 
    ){
      rc = SQLITE_OK;
      memset(zBuf, 0, iAmt);
    }else{
      rc = p->pReal->pMethods->xRead(p->pReal, zBuf, iAmt, iOfst);
    }
    if( rc==SQLITE_OK && iOfst==0 && (p->openFlags & SQLITE_OPEN_MAIN_DB) ){
      /* These look like magic numbers. But they are stable, as they are part
       ** of the definition of the SQLite file format, which may not change. */
      u8 *pBuf = (u8*)zBuf;
      p->iCookie = rbuGetU32(&pBuf[24]);
      p->iWriteVer = pBuf[19];
    }
  }
  return rc;
}

/*
** Write data to an rbuVfs-file.
*/
static int rbuVfsWrite(
  sqlite3_file *pFile, 
  const void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  rbu_file *p = (rbu_file*)pFile;
  sqlite3rbu *pRbu = p->pRbu;
  int rc;

  if( pRbu && pRbu->eStage==RBU_STAGE_CAPTURE ){
    assert( p->openFlags & SQLITE_OPEN_MAIN_DB );
    rc = rbuCaptureDbWrite(p->pRbu, iOfst);
  }else{
    if( pRbu && pRbu->eStage==RBU_STAGE_OAL 
     && (p->openFlags & SQLITE_OPEN_WAL) 
     && iOfst>=pRbu->iOalSz
    ){
      pRbu->iOalSz = iAmt + iOfst;
    }
    rc = p->pReal->pMethods->xWrite(p->pReal, zBuf, iAmt, iOfst);
    if( rc==SQLITE_OK && iOfst==0 && (p->openFlags & SQLITE_OPEN_MAIN_DB) ){
      /* These look like magic numbers. But they are stable, as they are part
      ** of the definition of the SQLite file format, which may not change. */
      u8 *pBuf = (u8*)zBuf;
      p->iCookie = rbuGetU32(&pBuf[24]);
      p->iWriteVer = pBuf[19];
    }
  }
  return rc;
}

/*
** Truncate an rbuVfs-file.
*/
static int rbuVfsTruncate(sqlite3_file *pFile, sqlite_int64 size){
  rbu_file *p = (rbu_file*)pFile;
  return p->pReal->pMethods->xTruncate(p->pReal, size);
}

/*
** Sync an rbuVfs-file.
*/
static int rbuVfsSync(sqlite3_file *pFile, int flags){
  rbu_file *p = (rbu_file *)pFile;
  if( p->pRbu && p->pRbu->eStage==RBU_STAGE_CAPTURE ){
    if( p->openFlags & SQLITE_OPEN_MAIN_DB ){
      return SQLITE_INTERNAL;
    }
    return SQLITE_OK;
  }
  return p->pReal->pMethods->xSync(p->pReal, flags);
}

/*
** Return the current file-size of an rbuVfs-file.
*/
static int rbuVfsFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
  rbu_file *p = (rbu_file *)pFile;
  return p->pReal->pMethods->xFileSize(p->pReal, pSize);
}

/*
** Lock an rbuVfs-file.
*/
static int rbuVfsLock(sqlite3_file *pFile, int eLock){
  rbu_file *p = (rbu_file*)pFile;
  sqlite3rbu *pRbu = p->pRbu;
  int rc = SQLITE_OK;

  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB) );
  if( pRbu && eLock==SQLITE_LOCK_EXCLUSIVE && pRbu->eStage!=RBU_STAGE_DONE ){
    /* Do not allow EXCLUSIVE locks. Preventing SQLite from taking this 
    ** prevents it from checkpointing the database from sqlite3_close(). */
    rc = SQLITE_BUSY;
  }else{
    rc = p->pReal->pMethods->xLock(p->pReal, eLock);
  }

  return rc;
}

/*
** Unlock an rbuVfs-file.
*/
static int rbuVfsUnlock(sqlite3_file *pFile, int eLock){
  rbu_file *p = (rbu_file *)pFile;
  return p->pReal->pMethods->xUnlock(p->pReal, eLock);
}

/*
** Check if another file-handle holds a RESERVED lock on an rbuVfs-file.
*/
static int rbuVfsCheckReservedLock(sqlite3_file *pFile, int *pResOut){
  rbu_file *p = (rbu_file *)pFile;
  return p->pReal->pMethods->xCheckReservedLock(p->pReal, pResOut);
}

/*
** File control method. For custom operations on an rbuVfs-file.
*/
static int rbuVfsFileControl(sqlite3_file *pFile, int op, void *pArg){
  rbu_file *p = (rbu_file *)pFile;
  int (*xControl)(sqlite3_file*,int,void*) = p->pReal->pMethods->xFileControl;
  int rc;

  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB)
       || p->openFlags & (SQLITE_OPEN_TRANSIENT_DB|SQLITE_OPEN_TEMP_JOURNAL)
  );
  if( op==SQLITE_FCNTL_RBU ){
    sqlite3rbu *pRbu = (sqlite3rbu*)pArg;

    /* First try to find another RBU vfs lower down in the vfs stack. If
    ** one is found, this vfs will operate in pass-through mode. The lower
    ** level vfs will do the special RBU handling.  */
    rc = xControl(p->pReal, op, pArg);

    if( rc==SQLITE_NOTFOUND ){
      /* Now search for a zipvfs instance lower down in the VFS stack. If
      ** one is found, this is an error.  */
      void *dummy = 0;
      rc = xControl(p->pReal, SQLITE_FCNTL_ZIPVFS, &dummy);
      if( rc==SQLITE_OK ){
        rc = SQLITE_ERROR;
        pRbu->zErrmsg = sqlite3_mprintf("rbu/zipvfs setup error");
      }else if( rc==SQLITE_NOTFOUND ){
        pRbu->pTargetFd = p;
        p->pRbu = pRbu;
        if( p->pWalFd ) p->pWalFd->pRbu = pRbu;
        rc = SQLITE_OK;
      }
    }
    return rc;
  }

  rc = xControl(p->pReal, op, pArg);
  if( rc==SQLITE_OK && op==SQLITE_FCNTL_VFSNAME ){
    rbu_vfs *pRbuVfs = p->pRbuVfs;
    char *zIn = *(char**)pArg;
    char *zOut = sqlite3_mprintf("rbu(%s)/%z", pRbuVfs->base.zName, zIn);
    *(char**)pArg = zOut;
    if( zOut==0 ) rc = SQLITE_NOMEM;
  }

  return rc;
}

/*
** Return the sector-size in bytes for an rbuVfs-file.
*/
static int rbuVfsSectorSize(sqlite3_file *pFile){
  rbu_file *p = (rbu_file *)pFile;
  return p->pReal->pMethods->xSectorSize(p->pReal);
}

/*
** Return the device characteristic flags supported by an rbuVfs-file.
*/
static int rbuVfsDeviceCharacteristics(sqlite3_file *pFile){
  rbu_file *p = (rbu_file *)pFile;
  return p->pReal->pMethods->xDeviceCharacteristics(p->pReal);
}

/*
** Take or release a shared-memory lock.
*/
static int rbuVfsShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
  rbu_file *p = (rbu_file*)pFile;
  sqlite3rbu *pRbu = p->pRbu;
  int rc = SQLITE_OK;

#ifdef SQLITE_AMALGAMATION
    assert( WAL_CKPT_LOCK==1 );
#endif

  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB) );
  if( pRbu && (pRbu->eStage==RBU_STAGE_OAL || pRbu->eStage==RBU_STAGE_MOVE) ){
    /* Magic number 1 is the WAL_CKPT_LOCK lock. Preventing SQLite from
    ** taking this lock also prevents any checkpoints from occurring. 
    ** todo: really, it's not clear why this might occur, as 
    ** wal_autocheckpoint ought to be turned off.  */
    if( ofst==WAL_LOCK_CKPT && n==1 ) rc = SQLITE_BUSY;
  }else{
    int bCapture = 0;
    if( n==1 && (flags & SQLITE_SHM_EXCLUSIVE)
     && pRbu && pRbu->eStage==RBU_STAGE_CAPTURE
     && (ofst==WAL_LOCK_WRITE || ofst==WAL_LOCK_CKPT || ofst==WAL_LOCK_READ0)
    ){
      bCapture = 1;
    }

    if( bCapture==0 || 0==(flags & SQLITE_SHM_UNLOCK) ){
      rc = p->pReal->pMethods->xShmLock(p->pReal, ofst, n, flags);
      if( bCapture && rc==SQLITE_OK ){
        pRbu->mLock |= (1 << ofst);
      }
    }
  }

  return rc;
}

/*
** Obtain a pointer to a mapping of a single 32KiB page of the *-shm file.
*/
static int rbuVfsShmMap(
  sqlite3_file *pFile, 
  int iRegion, 
  int szRegion, 
  int isWrite, 
  void volatile **pp
){
  rbu_file *p = (rbu_file*)pFile;
  int rc = SQLITE_OK;
  int eStage = (p->pRbu ? p->pRbu->eStage : 0);

  /* If not in RBU_STAGE_OAL, allow this call to pass through. Or, if this
  ** rbu is in the RBU_STAGE_OAL state, use heap memory for *-shm space 
  ** instead of a file on disk.  */
  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB) );
  if( eStage==RBU_STAGE_OAL || eStage==RBU_STAGE_MOVE ){
    if( iRegion<=p->nShm ){
      int nByte = (iRegion+1) * sizeof(char*);
      char **apNew = (char**)sqlite3_realloc(p->apShm, nByte);
      if( apNew==0 ){
        rc = SQLITE_NOMEM;
      }else{
        memset(&apNew[p->nShm], 0, sizeof(char*) * (1 + iRegion - p->nShm));
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  return rc;
}

/*
** Memory barrier.
*/
static void otaVfsShmBarrier(sqlite3_file *pFile){
  ota_file *p = (ota_file *)pFile;
  p->pReal->pMethods->xShmBarrier(p->pReal);
}

/*
** The xShmUnmap method.
*/
static int otaVfsShmUnmap(sqlite3_file *pFile, int delFlag){
  ota_file *p = (ota_file*)pFile;
  int rc = SQLITE_OK;
  int eStage = (p->pOta ? p->pOta->eStage : 0);

  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB) );
  if( eStage==OTA_STAGE_OAL || eStage==OTA_STAGE_MOVE ){
    /* no-op */
  }else{
    /* Release the checkpointer and writer locks */
    otaUnlockShm(p);
    rc = p->pReal->pMethods->xShmUnmap(p->pReal, delFlag);
  }
  return rc;
}

/*
** Given that zWal points to a buffer containing a wal file name passed to 
** either the xOpen() or xAccess() VFS method, return a pointer to the
** file-handle opened by the same database connection on the corresponding
** database file.
*/
static ota_file *otaFindMaindb(ota_vfs *pOtaVfs, const char *zWal){
  ota_file *pDb;
  sqlite3_mutex_enter(pOtaVfs->mutex);
  for(pDb=pOtaVfs->pMain; pDb && pDb->zWal!=zWal; pDb=pDb->pMainNext);
  sqlite3_mutex_leave(pOtaVfs->mutex);
  return pDb;
}

/*
** Open an ota file handle.
*/
static int otaVfsOpen(
  sqlite3_vfs *pVfs,
  const char *zName,
  sqlite3_file *pFile,
  int flags,
  int *pOutFlags
){
  static sqlite3_io_methods otavfs_io_methods = {
    2,                            /* iVersion */
    otaVfsClose,                  /* xClose */
    otaVfsRead,                   /* xRead */
    otaVfsWrite,                  /* xWrite */
    otaVfsTruncate,               /* xTruncate */
    otaVfsSync,                   /* xSync */
    otaVfsFileSize,               /* xFileSize */
    otaVfsLock,                   /* xLock */
    otaVfsUnlock,                 /* xUnlock */
    otaVfsCheckReservedLock,      /* xCheckReservedLock */
    otaVfsFileControl,            /* xFileControl */
    otaVfsSectorSize,             /* xSectorSize */
    otaVfsDeviceCharacteristics,  /* xDeviceCharacteristics */
    otaVfsShmMap,                 /* xShmMap */
    otaVfsShmLock,                /* xShmLock */
    otaVfsShmBarrier,             /* xShmBarrier */
    otaVfsShmUnmap                /* xShmUnmap */
  };
  ota_vfs *pOtaVfs = (ota_vfs*)pVfs;
  sqlite3_vfs *pRealVfs = pOtaVfs->pRealVfs;
  ota_file *pFd = (ota_file *)pFile;
  int rc = SQLITE_OK;
  const char *zOpen = zName;

  memset(pFd, 0, sizeof(ota_file));
  pFd->pReal = (sqlite3_file*)&pFd[1];
  pFd->pOtaVfs = pOtaVfs;
  pFd->openFlags = flags;
  if( zName ){
    if( flags & SQLITE_OPEN_MAIN_DB ){
      /* A main database has just been opened. The following block sets
      ** (pFd->zWal) to point to a buffer owned by SQLite that contains
      ** the name of the *-wal file this db connection will use. SQLite
      ** happens to pass a pointer to this buffer when using xAccess()







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  return rc;
}

/*
** Memory barrier.
*/
static void rbuVfsShmBarrier(sqlite3_file *pFile){
  rbu_file *p = (rbu_file *)pFile;
  p->pReal->pMethods->xShmBarrier(p->pReal);
}

/*
** The xShmUnmap method.
*/
static int rbuVfsShmUnmap(sqlite3_file *pFile, int delFlag){
  rbu_file *p = (rbu_file*)pFile;
  int rc = SQLITE_OK;
  int eStage = (p->pRbu ? p->pRbu->eStage : 0);

  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB) );
  if( eStage==RBU_STAGE_OAL || eStage==RBU_STAGE_MOVE ){
    /* no-op */
  }else{
    /* Release the checkpointer and writer locks */
    rbuUnlockShm(p);
    rc = p->pReal->pMethods->xShmUnmap(p->pReal, delFlag);
  }
  return rc;
}

/*
** Given that zWal points to a buffer containing a wal file name passed to 
** either the xOpen() or xAccess() VFS method, return a pointer to the
** file-handle opened by the same database connection on the corresponding
** database file.
*/
static rbu_file *rbuFindMaindb(rbu_vfs *pRbuVfs, const char *zWal){
  rbu_file *pDb;
  sqlite3_mutex_enter(pRbuVfs->mutex);
  for(pDb=pRbuVfs->pMain; pDb && pDb->zWal!=zWal; pDb=pDb->pMainNext);
  sqlite3_mutex_leave(pRbuVfs->mutex);
  return pDb;
}

/*
** Open an rbu file handle.
*/
static int rbuVfsOpen(
  sqlite3_vfs *pVfs,
  const char *zName,
  sqlite3_file *pFile,
  int flags,
  int *pOutFlags
){
  static sqlite3_io_methods rbuvfs_io_methods = {
    2,                            /* iVersion */
    rbuVfsClose,                  /* xClose */
    rbuVfsRead,                   /* xRead */
    rbuVfsWrite,                  /* xWrite */
    rbuVfsTruncate,               /* xTruncate */
    rbuVfsSync,                   /* xSync */
    rbuVfsFileSize,               /* xFileSize */
    rbuVfsLock,                   /* xLock */
    rbuVfsUnlock,                 /* xUnlock */
    rbuVfsCheckReservedLock,      /* xCheckReservedLock */
    rbuVfsFileControl,            /* xFileControl */
    rbuVfsSectorSize,             /* xSectorSize */
    rbuVfsDeviceCharacteristics,  /* xDeviceCharacteristics */
    rbuVfsShmMap,                 /* xShmMap */
    rbuVfsShmLock,                /* xShmLock */
    rbuVfsShmBarrier,             /* xShmBarrier */
    rbuVfsShmUnmap                /* xShmUnmap */
  };
  rbu_vfs *pRbuVfs = (rbu_vfs*)pVfs;
  sqlite3_vfs *pRealVfs = pRbuVfs->pRealVfs;
  rbu_file *pFd = (rbu_file *)pFile;
  int rc = SQLITE_OK;
  const char *zOpen = zName;

  memset(pFd, 0, sizeof(rbu_file));
  pFd->pReal = (sqlite3_file*)&pFd[1];
  pFd->pRbuVfs = pRbuVfs;
  pFd->openFlags = flags;
  if( zName ){
    if( flags & SQLITE_OPEN_MAIN_DB ){
      /* A main database has just been opened. The following block sets
      ** (pFd->zWal) to point to a buffer owned by SQLite that contains
      ** the name of the *-wal file this db connection will use. SQLite
      ** happens to pass a pointer to this buffer when using xAccess()
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      }else{
        while( *z==0 ) z++;
      }
      z += (n + 8 + 1);
      pFd->zWal = z;
    }
    else if( flags & SQLITE_OPEN_WAL ){
      ota_file *pDb = otaFindMaindb(pOtaVfs, zName);
      if( pDb ){
        if( pDb->pOta && pDb->pOta->eStage==OTA_STAGE_OAL ){
          /* This call is to open a *-wal file. Intead, open the *-oal. This
          ** code ensures that the string passed to xOpen() is terminated by a
          ** pair of '\0' bytes in case the VFS attempts to extract a URI 
          ** parameter from it.  */
          int nCopy = strlen(zName);
          char *zCopy = sqlite3_malloc(nCopy+2);
          if( zCopy ){
            memcpy(zCopy, zName, nCopy);
            zCopy[nCopy-3] = 'o';
            zCopy[nCopy] = '\0';
            zCopy[nCopy+1] = '\0';
            zOpen = (const char*)(pFd->zDel = zCopy);
          }else{
            rc = SQLITE_NOMEM;
          }
          pFd->pOta = pDb->pOta;
        }
        pDb->pWalFd = pFd;
      }
    }
  }

  if( rc==SQLITE_OK ){
    rc = pRealVfs->xOpen(pRealVfs, zOpen, pFd->pReal, flags, pOutFlags);
  }
  if( pFd->pReal->pMethods ){
    /* The xOpen() operation has succeeded. Set the sqlite3_file.pMethods
    ** pointer and, if the file is a main database file, link it into the
    ** mutex protected linked list of all such files.  */
    pFile->pMethods = &otavfs_io_methods;
    if( flags & SQLITE_OPEN_MAIN_DB ){
      sqlite3_mutex_enter(pOtaVfs->mutex);
      pFd->pMainNext = pOtaVfs->pMain;
      pOtaVfs->pMain = pFd;
      sqlite3_mutex_leave(pOtaVfs->mutex);
    }
  }else{
    sqlite3_free(pFd->zDel);
  }

  return rc;
}

/*
** Delete the file located at zPath.
*/
static int otaVfsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xDelete(pRealVfs, zPath, dirSync);
}

/*
** Test for access permissions. Return true if the requested permission
** is available, or false otherwise.
*/
static int otaVfsAccess(
  sqlite3_vfs *pVfs, 
  const char *zPath, 
  int flags, 
  int *pResOut
){
  ota_vfs *pOtaVfs = (ota_vfs*)pVfs;
  sqlite3_vfs *pRealVfs = pOtaVfs->pRealVfs;
  int rc;

  rc = pRealVfs->xAccess(pRealVfs, zPath, flags, pResOut);

  /* If this call is to check if a *-wal file associated with an OTA target
  ** database connection exists, and the OTA update is in OTA_STAGE_OAL,
  ** the following special handling is activated:
  **
  **   a) if the *-wal file does exist, return SQLITE_CANTOPEN. This
  **      ensures that the OTA extension never tries to update a database
  **      in wal mode, even if the first page of the database file has
  **      been damaged. 
  **
  **   b) if the *-wal file does not exist, claim that it does anyway,
  **      causing SQLite to call xOpen() to open it. This call will also
  **      be intercepted (see the otaVfsOpen() function) and the *-oal
  **      file opened instead.
  */
  if( rc==SQLITE_OK && flags==SQLITE_ACCESS_EXISTS ){
    ota_file *pDb = otaFindMaindb(pOtaVfs, zPath);
    if( pDb && pDb->pOta && pDb->pOta->eStage==OTA_STAGE_OAL ){
      if( *pResOut ){
        rc = SQLITE_CANTOPEN;
      }else{
        *pResOut = 1;
      }
    }
  }

  return rc;
}

/*
** Populate buffer zOut with the full canonical pathname corresponding
** to the pathname in zPath. zOut is guaranteed to point to a buffer
** of at least (DEVSYM_MAX_PATHNAME+1) bytes.
*/
static int otaVfsFullPathname(
  sqlite3_vfs *pVfs, 
  const char *zPath, 
  int nOut, 
  char *zOut
){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xFullPathname(pRealVfs, zPath, nOut, zOut);
}

#ifndef SQLITE_OMIT_LOAD_EXTENSION
/*
** Open the dynamic library located at zPath and return a handle.
*/
static void *otaVfsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xDlOpen(pRealVfs, zPath);
}

/*
** Populate the buffer zErrMsg (size nByte bytes) with a human readable
** utf-8 string describing the most recent error encountered associated 
** with dynamic libraries.
*/
static void otaVfsDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  pRealVfs->xDlError(pRealVfs, nByte, zErrMsg);
}

/*
** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
*/
static void (*otaVfsDlSym(
  sqlite3_vfs *pVfs, 
  void *pArg, 
  const char *zSym
))(void){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xDlSym(pRealVfs, pArg, zSym);
}

/*
** Close the dynamic library handle pHandle.
*/
static void otaVfsDlClose(sqlite3_vfs *pVfs, void *pHandle){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xDlClose(pRealVfs, pHandle);
}
#endif /* SQLITE_OMIT_LOAD_EXTENSION */

/*
** Populate the buffer pointed to by zBufOut with nByte bytes of 
** random data.
*/
static int otaVfsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xRandomness(pRealVfs, nByte, zBufOut);
}

/*
** Sleep for nMicro microseconds. Return the number of microseconds 
** actually slept.
*/
static int otaVfsSleep(sqlite3_vfs *pVfs, int nMicro){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xSleep(pRealVfs, nMicro);
}

/*
** Return the current time as a Julian Day number in *pTimeOut.
*/
static int otaVfsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
  sqlite3_vfs *pRealVfs = ((ota_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xCurrentTime(pRealVfs, pTimeOut);
}

/*
** No-op.
*/
static int otaVfsGetLastError(sqlite3_vfs *pVfs, int a, char *b){
  return 0;
}

/*
** Deregister and destroy an OTA vfs created by an earlier call to
** sqlite3ota_create_vfs().
*/
SQLITE_API void SQLITE_STDCALL sqlite3ota_destroy_vfs(const char *zName){
  sqlite3_vfs *pVfs = sqlite3_vfs_find(zName);
  if( pVfs && pVfs->xOpen==otaVfsOpen ){
    sqlite3_mutex_free(((ota_vfs*)pVfs)->mutex);
    sqlite3_vfs_unregister(pVfs);
    sqlite3_free(pVfs);
  }
}

/*
** Create an OTA VFS named zName that accesses the underlying file-system
** via existing VFS zParent. The new object is registered as a non-default
** VFS with SQLite before returning.
*/
SQLITE_API int SQLITE_STDCALL sqlite3ota_create_vfs(const char *zName, const char *zParent){

  /* Template for VFS */
  static sqlite3_vfs vfs_template = {
    1,                            /* iVersion */
    0,                            /* szOsFile */
    0,                            /* mxPathname */
    0,                            /* pNext */
    0,                            /* zName */
    0,                            /* pAppData */
    otaVfsOpen,                   /* xOpen */
    otaVfsDelete,                 /* xDelete */
    otaVfsAccess,                 /* xAccess */
    otaVfsFullPathname,           /* xFullPathname */

#ifndef SQLITE_OMIT_LOAD_EXTENSION
    otaVfsDlOpen,                 /* xDlOpen */
    otaVfsDlError,                /* xDlError */
    otaVfsDlSym,                  /* xDlSym */
    otaVfsDlClose,                /* xDlClose */
#else
    0, 0, 0, 0,
#endif

    otaVfsRandomness,             /* xRandomness */
    otaVfsSleep,                  /* xSleep */
    otaVfsCurrentTime,            /* xCurrentTime */
    otaVfsGetLastError,           /* xGetLastError */
    0,                            /* xCurrentTimeInt64 (version 2) */
    0, 0, 0                       /* Unimplemented version 3 methods */
  };

  ota_vfs *pNew = 0;              /* Newly allocated VFS */
  int nName;
  int rc = SQLITE_OK;

  int nByte;
  nName = strlen(zName);
  nByte = sizeof(ota_vfs) + nName + 1;
  pNew = (ota_vfs*)sqlite3_malloc(nByte);
  if( pNew==0 ){
    rc = SQLITE_NOMEM;
  }else{
    sqlite3_vfs *pParent;           /* Parent VFS */
    memset(pNew, 0, nByte);
    pParent = sqlite3_vfs_find(zParent);
    if( pParent==0 ){
      rc = SQLITE_NOTFOUND;
    }else{
      char *zSpace;
      memcpy(&pNew->base, &vfs_template, sizeof(sqlite3_vfs));
      pNew->base.mxPathname = pParent->mxPathname;
      pNew->base.szOsFile = sizeof(ota_file) + pParent->szOsFile;
      pNew->pRealVfs = pParent;
      pNew->base.zName = (const char*)(zSpace = (char*)&pNew[1]);
      memcpy(zSpace, zName, nName);

      /* Allocate the mutex and register the new VFS (not as the default) */
      pNew->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_RECURSIVE);
      if( pNew->mutex==0 ){







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      }else{
        while( *z==0 ) z++;
      }
      z += (n + 8 + 1);
      pFd->zWal = z;
    }
    else if( flags & SQLITE_OPEN_WAL ){
      rbu_file *pDb = rbuFindMaindb(pRbuVfs, zName);
      if( pDb ){
        if( pDb->pRbu && pDb->pRbu->eStage==RBU_STAGE_OAL ){
          /* This call is to open a *-wal file. Intead, open the *-oal. This
          ** code ensures that the string passed to xOpen() is terminated by a
          ** pair of '\0' bytes in case the VFS attempts to extract a URI 
          ** parameter from it.  */
          int nCopy = strlen(zName);
          char *zCopy = sqlite3_malloc(nCopy+2);
          if( zCopy ){
            memcpy(zCopy, zName, nCopy);
            zCopy[nCopy-3] = 'o';
            zCopy[nCopy] = '\0';
            zCopy[nCopy+1] = '\0';
            zOpen = (const char*)(pFd->zDel = zCopy);
          }else{
            rc = SQLITE_NOMEM;
          }
          pFd->pRbu = pDb->pRbu;
        }
        pDb->pWalFd = pFd;
      }
    }
  }

  if( rc==SQLITE_OK ){
    rc = pRealVfs->xOpen(pRealVfs, zOpen, pFd->pReal, flags, pOutFlags);
  }
  if( pFd->pReal->pMethods ){
    /* The xOpen() operation has succeeded. Set the sqlite3_file.pMethods
    ** pointer and, if the file is a main database file, link it into the
    ** mutex protected linked list of all such files.  */
    pFile->pMethods = &rbuvfs_io_methods;
    if( flags & SQLITE_OPEN_MAIN_DB ){
      sqlite3_mutex_enter(pRbuVfs->mutex);
      pFd->pMainNext = pRbuVfs->pMain;
      pRbuVfs->pMain = pFd;
      sqlite3_mutex_leave(pRbuVfs->mutex);
    }
  }else{
    sqlite3_free(pFd->zDel);
  }

  return rc;
}

/*
** Delete the file located at zPath.
*/
static int rbuVfsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xDelete(pRealVfs, zPath, dirSync);
}

/*
** Test for access permissions. Return true if the requested permission
** is available, or false otherwise.
*/
static int rbuVfsAccess(
  sqlite3_vfs *pVfs, 
  const char *zPath, 
  int flags, 
  int *pResOut
){
  rbu_vfs *pRbuVfs = (rbu_vfs*)pVfs;
  sqlite3_vfs *pRealVfs = pRbuVfs->pRealVfs;
  int rc;

  rc = pRealVfs->xAccess(pRealVfs, zPath, flags, pResOut);

  /* If this call is to check if a *-wal file associated with an RBU target
  ** database connection exists, and the RBU update is in RBU_STAGE_OAL,
  ** the following special handling is activated:
  **
  **   a) if the *-wal file does exist, return SQLITE_CANTOPEN. This
  **      ensures that the RBU extension never tries to update a database
  **      in wal mode, even if the first page of the database file has
  **      been damaged. 
  **
  **   b) if the *-wal file does not exist, claim that it does anyway,
  **      causing SQLite to call xOpen() to open it. This call will also
  **      be intercepted (see the rbuVfsOpen() function) and the *-oal
  **      file opened instead.
  */
  if( rc==SQLITE_OK && flags==SQLITE_ACCESS_EXISTS ){
    rbu_file *pDb = rbuFindMaindb(pRbuVfs, zPath);
    if( pDb && pDb->pRbu && pDb->pRbu->eStage==RBU_STAGE_OAL ){
      if( *pResOut ){
        rc = SQLITE_CANTOPEN;
      }else{
        *pResOut = 1;
      }
    }
  }

  return rc;
}

/*
** Populate buffer zOut with the full canonical pathname corresponding
** to the pathname in zPath. zOut is guaranteed to point to a buffer
** of at least (DEVSYM_MAX_PATHNAME+1) bytes.
*/
static int rbuVfsFullPathname(
  sqlite3_vfs *pVfs, 
  const char *zPath, 
  int nOut, 
  char *zOut
){
  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xFullPathname(pRealVfs, zPath, nOut, zOut);
}

#ifndef SQLITE_OMIT_LOAD_EXTENSION
/*
** Open the dynamic library located at zPath and return a handle.
*/
static void *rbuVfsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xDlOpen(pRealVfs, zPath);
}

/*
** Populate the buffer zErrMsg (size nByte bytes) with a human readable
** utf-8 string describing the most recent error encountered associated 
** with dynamic libraries.
*/
static void rbuVfsDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
  pRealVfs->xDlError(pRealVfs, nByte, zErrMsg);
}

/*
** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
*/
static void (*rbuVfsDlSym(
  sqlite3_vfs *pVfs, 
  void *pArg, 
  const char *zSym
))(void){
  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xDlSym(pRealVfs, pArg, zSym);
}

/*
** Close the dynamic library handle pHandle.
*/
static void rbuVfsDlClose(sqlite3_vfs *pVfs, void *pHandle){
  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xDlClose(pRealVfs, pHandle);
}
#endif /* SQLITE_OMIT_LOAD_EXTENSION */

/*
** Populate the buffer pointed to by zBufOut with nByte bytes of 
** random data.
*/
static int rbuVfsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xRandomness(pRealVfs, nByte, zBufOut);
}

/*
** Sleep for nMicro microseconds. Return the number of microseconds 
** actually slept.
*/
static int rbuVfsSleep(sqlite3_vfs *pVfs, int nMicro){
  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xSleep(pRealVfs, nMicro);
}

/*
** Return the current time as a Julian Day number in *pTimeOut.
*/
static int rbuVfsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
  return pRealVfs->xCurrentTime(pRealVfs, pTimeOut);
}

/*
** No-op.
*/
static int rbuVfsGetLastError(sqlite3_vfs *pVfs, int a, char *b){
  return 0;
}

/*
** Deregister and destroy an RBU vfs created by an earlier call to
** sqlite3rbu_create_vfs().
*/
SQLITE_API void SQLITE_STDCALL sqlite3rbu_destroy_vfs(const char *zName){
  sqlite3_vfs *pVfs = sqlite3_vfs_find(zName);
  if( pVfs && pVfs->xOpen==rbuVfsOpen ){
    sqlite3_mutex_free(((rbu_vfs*)pVfs)->mutex);
    sqlite3_vfs_unregister(pVfs);
    sqlite3_free(pVfs);
  }
}

/*
** Create an RBU VFS named zName that accesses the underlying file-system
** via existing VFS zParent. The new object is registered as a non-default
** VFS with SQLite before returning.
*/
SQLITE_API int SQLITE_STDCALL sqlite3rbu_create_vfs(const char *zName, const char *zParent){

  /* Template for VFS */
  static sqlite3_vfs vfs_template = {
    1,                            /* iVersion */
    0,                            /* szOsFile */
    0,                            /* mxPathname */
    0,                            /* pNext */
    0,                            /* zName */
    0,                            /* pAppData */
    rbuVfsOpen,                   /* xOpen */
    rbuVfsDelete,                 /* xDelete */
    rbuVfsAccess,                 /* xAccess */
    rbuVfsFullPathname,           /* xFullPathname */

#ifndef SQLITE_OMIT_LOAD_EXTENSION
    rbuVfsDlOpen,                 /* xDlOpen */
    rbuVfsDlError,                /* xDlError */
    rbuVfsDlSym,                  /* xDlSym */
    rbuVfsDlClose,                /* xDlClose */
#else
    0, 0, 0, 0,
#endif

    rbuVfsRandomness,             /* xRandomness */
    rbuVfsSleep,                  /* xSleep */
    rbuVfsCurrentTime,            /* xCurrentTime */
    rbuVfsGetLastError,           /* xGetLastError */
    0,                            /* xCurrentTimeInt64 (version 2) */
    0, 0, 0                       /* Unimplemented version 3 methods */
  };

  rbu_vfs *pNew = 0;              /* Newly allocated VFS */
  int nName;
  int rc = SQLITE_OK;

  int nByte;
  nName = strlen(zName);
  nByte = sizeof(rbu_vfs) + nName + 1;
  pNew = (rbu_vfs*)sqlite3_malloc(nByte);
  if( pNew==0 ){
    rc = SQLITE_NOMEM;
  }else{
    sqlite3_vfs *pParent;           /* Parent VFS */
    memset(pNew, 0, nByte);
    pParent = sqlite3_vfs_find(zParent);
    if( pParent==0 ){
      rc = SQLITE_NOTFOUND;
    }else{
      char *zSpace;
      memcpy(&pNew->base, &vfs_template, sizeof(sqlite3_vfs));
      pNew->base.mxPathname = pParent->mxPathname;
      pNew->base.szOsFile = sizeof(rbu_file) + pParent->szOsFile;
      pNew->pRealVfs = pParent;
      pNew->base.zName = (const char*)(zSpace = (char*)&pNew[1]);
      memcpy(zSpace, zName, nName);

      /* Allocate the mutex and register the new VFS (not as the default) */
      pNew->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_RECURSIVE);
      if( pNew->mutex==0 ){
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  return rc;
}


/**************************************************************************/

#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_OTA) */

/************** End of sqlite3ota.c ******************************************/
/************** Begin file dbstat.c ******************************************/
/*
** 2010 July 12
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**







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  return rc;
}


/**************************************************************************/

#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_RBU) */

/************** End of sqlite3rbu.c ******************************************/
/************** Begin file dbstat.c ******************************************/
/*
** 2010 July 12
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
Changes to SQLite.Interop/src/core/sqlite3.h.
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**
** See also: [sqlite3_libversion()],
** [sqlite3_libversion_number()], [sqlite3_sourceid()],
** [sqlite_version()] and [sqlite_source_id()].
*/
#define SQLITE_VERSION        "3.8.11"
#define SQLITE_VERSION_NUMBER 3008011
#define SQLITE_SOURCE_ID      "2015-07-21 19:22:35 01c8b9ccfa0f336dfead7c004de3de571753f707"

/*
** CAPI3REF: Run-Time Library Version Numbers
** KEYWORDS: sqlite3_version, sqlite3_sourceid
**
** These interfaces provide the same information as the [SQLITE_VERSION],
** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros







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**
** See also: [sqlite3_libversion()],
** [sqlite3_libversion_number()], [sqlite3_sourceid()],
** [sqlite_version()] and [sqlite_source_id()].
*/
#define SQLITE_VERSION        "3.8.11"
#define SQLITE_VERSION_NUMBER 3008011
#define SQLITE_SOURCE_ID      "2015-07-24 00:02:15 119883a21bdcab66c15d1e80f3da20addda328ad"

/*
** CAPI3REF: Run-Time Library Version Numbers
** KEYWORDS: sqlite3_version, sqlite3_sourceid
**
** These interfaces provide the same information as the [SQLITE_VERSION],
** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros
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** circumstances in order to fix a problem with priority inversion.
** Applications should <em>not</em> use this file-control.
**
** <li>[[SQLITE_FCNTL_ZIPVFS]]
** The [SQLITE_FCNTL_ZIPVFS] opcode is implemented by zipvfs only. All other
** VFS should return SQLITE_NOTFOUND for this opcode.
**
** <li>[[SQLITE_FCNTL_OTA]]
** The [SQLITE_FCNTL_OTA] opcode is implemented by the special VFS used by
** the OTA extension only.  All other VFS should return SQLITE_NOTFOUND for
** this opcode.  
** </ul>
*/
#define SQLITE_FCNTL_LOCKSTATE               1
#define SQLITE_FCNTL_GET_LOCKPROXYFILE       2
#define SQLITE_FCNTL_SET_LOCKPROXYFILE       3
#define SQLITE_FCNTL_LAST_ERRNO              4







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** circumstances in order to fix a problem with priority inversion.
** Applications should <em>not</em> use this file-control.
**
** <li>[[SQLITE_FCNTL_ZIPVFS]]
** The [SQLITE_FCNTL_ZIPVFS] opcode is implemented by zipvfs only. All other
** VFS should return SQLITE_NOTFOUND for this opcode.
**
** <li>[[SQLITE_FCNTL_RBU]]
** The [SQLITE_FCNTL_RBU] opcode is implemented by the special VFS used by
** the RBU extension only.  All other VFS should return SQLITE_NOTFOUND for
** this opcode.  
** </ul>
*/
#define SQLITE_FCNTL_LOCKSTATE               1
#define SQLITE_FCNTL_GET_LOCKPROXYFILE       2
#define SQLITE_FCNTL_SET_LOCKPROXYFILE       3
#define SQLITE_FCNTL_LAST_ERRNO              4
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#define SQLITE_FCNTL_TRACE                  19
#define SQLITE_FCNTL_HAS_MOVED              20
#define SQLITE_FCNTL_SYNC                   21
#define SQLITE_FCNTL_COMMIT_PHASETWO        22
#define SQLITE_FCNTL_WIN32_SET_HANDLE       23
#define SQLITE_FCNTL_WAL_BLOCK              24
#define SQLITE_FCNTL_ZIPVFS                 25
#define SQLITE_FCNTL_OTA                    26

/* deprecated names */
#define SQLITE_GET_LOCKPROXYFILE      SQLITE_FCNTL_GET_LOCKPROXYFILE
#define SQLITE_SET_LOCKPROXYFILE      SQLITE_FCNTL_SET_LOCKPROXYFILE
#define SQLITE_LAST_ERRNO             SQLITE_FCNTL_LAST_ERRNO









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#define SQLITE_FCNTL_TRACE                  19
#define SQLITE_FCNTL_HAS_MOVED              20
#define SQLITE_FCNTL_SYNC                   21
#define SQLITE_FCNTL_COMMIT_PHASETWO        22
#define SQLITE_FCNTL_WIN32_SET_HANDLE       23
#define SQLITE_FCNTL_WAL_BLOCK              24
#define SQLITE_FCNTL_ZIPVFS                 25
#define SQLITE_FCNTL_RBU                    26

/* deprecated names */
#define SQLITE_GET_LOCKPROXYFILE      SQLITE_FCNTL_GET_LOCKPROXYFILE
#define SQLITE_SET_LOCKPROXYFILE      SQLITE_FCNTL_SET_LOCKPROXYFILE
#define SQLITE_LAST_ERRNO             SQLITE_FCNTL_LAST_ERRNO