System.Data.SQLite
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/********************************************************
 * ADO.NET 2.0 Data Provider for SQLite Version 3.X
 * Written by Joe Mistachkin (joe@mistachkin.com)
 *
 * Released to the public domain, use at your own risk!
 ********************************************************/

namespace System.Data.SQLite
{
    #region ISQLiteNativeModule Interface
    /// <summary>
    /// This interface represents a virtual table implementation written in
    /// native code.
    /// </summary>
    public interface ISQLiteNativeModule
    {
        /// <summary>
        /// <para>
        /// This method is called to create a new instance of a virtual table
        /// in response to a CREATE VIRTUAL TABLE statement. The db parameter
        /// is a pointer to the SQLite database connection that is executing
        /// the CREATE VIRTUAL TABLE statement. The pAux argument is the copy
        /// of the client data pointer that was the fourth argument to the
        /// sqlite3_create_module() or sqlite3_create_module_v2() call that
        /// registered the virtual table module. The argv parameter is an
        /// array of argc pointers to null terminated strings. The first
        /// string, argv[0], is the name of the module being invoked. The
        /// module name is the name provided as the second argument to
        /// sqlite3_create_module() and as the argument to the USING clause of
        /// the CREATE VIRTUAL TABLE statement that is running. The second,
        /// argv[1], is the name of the database in which the new virtual table
        /// is being created. The database name is "main" for the primary
        /// database, or "temp" for TEMP database, or the name given at the
        /// end of the ATTACH statement for attached databases. The third
        /// element of the array, argv[2], is the name of the new virtual
        /// table, as specified following the TABLE keyword in the CREATE
        /// VIRTUAL TABLE statement. If present, the fourth and subsequent
        /// strings in the argv[] array report the arguments to the module name
        /// in the CREATE VIRTUAL TABLE statement.
        /// </para>
        /// <para>
        /// The job of this method is to construct the new virtual table object
        /// (an sqlite3_vtab object) and return a pointer to it in *ppVTab.
        /// </para>
        /// <para>
        /// As part of the task of creating a new sqlite3_vtab structure, this
        /// method must invoke sqlite3_declare_vtab() to tell the SQLite core
        /// about the columns and datatypes in the virtual table. The
        /// sqlite3_declare_vtab() API has the following prototype:
        /// </para>
        /// <para>
        /// <code>
        /// int sqlite3_declare_vtab(sqlite3 *db, const char *zCreateTable)
        /// </code>
        /// </para>
        /// <para>
        /// The first argument to sqlite3_declare_vtab() must be the same
        /// database connection pointer as the first parameter to this method.
        /// The second argument to sqlite3_declare_vtab() must a
        /// zero-terminated UTF-8 string that contains a well-formed CREATE
        /// TABLE statement that defines the columns in the virtual table and
        /// their data types. The name of the table in this CREATE TABLE
        /// statement is ignored, as are all constraints. Only the column names
        /// and datatypes matter. The CREATE TABLE statement string need not to
        /// be held in persistent memory. The string can be deallocated and/or
        /// reused as soon as the sqlite3_declare_vtab() routine returns.
        /// </para>
        /// </summary>
        /// <param name="pDb">
        /// The native database connection handle.
        /// </param>
        /// <param name="pAux">
        /// The original native pointer value that was provided to the
        /// sqlite3_create_module(), sqlite3_create_module_v2() or
        /// sqlite3_create_disposable_module() functions.
        /// </param>
        /// <param name="argc">
        /// The number of arguments from the CREATE VIRTUAL TABLE statement.
        /// </param>
        /// <param name="argv">
        /// The array of string arguments from the CREATE VIRTUAL TABLE
        /// statement.
        /// </param>
        /// <param name="pVtab">
        /// Upon success, this parameter must be modified to point to the newly
        /// created native sqlite3_vtab derived structure.
        /// </param>
        /// <param name="pError">
        /// Upon failure, this parameter must be modified to point to the error
        /// message, with the underlying memory having been obtained from the
        /// sqlite3_malloc() function.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xCreate(
            IntPtr pDb,
            IntPtr pAux,
            int argc,
            IntPtr argv,
            ref IntPtr pVtab,
            ref IntPtr pError
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// The xConnect method is very similar to xCreate. It has the same
        /// parameters and constructs a new sqlite3_vtab structure just like
        /// xCreate. And it must also call sqlite3_declare_vtab() like xCreate.
        /// </para>
        /// <para>
        /// The difference is that xConnect is called to establish a new
        /// connection to an existing virtual table whereas xCreate is called
        /// to create a new virtual table from scratch.
        /// </para>
        /// <para>
        /// The xCreate and xConnect methods are only different when the
        /// virtual table has some kind of backing store that must be
        /// initialized the first time the virtual table is created. The
        /// xCreate method creates and initializes the backing store. The
        /// xConnect method just connects to an existing backing store.
        /// </para>
        /// <para>
        /// As an example, consider a virtual table implementation that
        /// provides read-only access to existing comma-separated-value (CSV)
        /// files on disk. There is no backing store that needs to be created
        /// or initialized for such a virtual table (since the CSV files
        /// already exist on disk) so the xCreate and xConnect methods will be
        /// identical for that module.
        /// </para>
        /// <para>
        /// Another example is a virtual table that implements a full-text
        /// index. The xCreate method must create and initialize data
        /// structures to hold the dictionary and posting lists for that index.
        /// The xConnect method, on the other hand, only has to locate and use
        /// an existing dictionary and posting lists that were created by a
        /// prior xCreate call.
        /// </para>
        /// <para>
        /// The xConnect method must return SQLITE_OK if it is successful in
        /// creating the new virtual table, or SQLITE_ERROR if it is not
        /// successful. If not successful, the sqlite3_vtab structure must not
        /// be allocated. An error message may optionally be returned in *pzErr
        /// if unsuccessful. Space to hold the error message string must be
        /// allocated using an SQLite memory allocation function like
        /// sqlite3_malloc() or sqlite3_mprintf() as the SQLite core will
        /// attempt to free the space using sqlite3_free() after the error has
        /// been reported up to the application.
        /// </para>
        /// <para>
        /// The xConnect method is required for every virtual table
        /// implementation, though the xCreate and xConnect pointers of the
        /// sqlite3_module object may point to the same function the virtual
        /// table does not need to initialize backing store.
        /// </para>
        /// </summary>
        /// <param name="pDb">
        /// The native database connection handle.
        /// </param>
        /// <param name="pAux">
        /// The original native pointer value that was provided to the
        /// sqlite3_create_module(), sqlite3_create_module_v2() or
        /// sqlite3_create_disposable_module() functions.
        /// </param>
        /// <param name="argc">
        /// The number of arguments from the CREATE VIRTUAL TABLE statement.
        /// </param>
        /// <param name="argv">
        /// The array of string arguments from the CREATE VIRTUAL TABLE
        /// statement.
        /// </param>
        /// <param name="pVtab">
        /// Upon success, this parameter must be modified to point to the newly
        /// created native sqlite3_vtab derived structure.
        /// </param>
        /// <param name="pError">
        /// Upon failure, this parameter must be modified to point to the error
        /// message, with the underlying memory having been obtained from the
        /// sqlite3_malloc() function.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xConnect(
            IntPtr pDb,
            IntPtr pAux,
            int argc,
            IntPtr argv,
            ref IntPtr pVtab,
            ref IntPtr pError
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// SQLite uses the xBestIndex method of a virtual table module to
        /// determine the best way to access the virtual table. The xBestIndex
        /// method has a prototype like this:
        /// </para>
        /// <code>
        /// int (*xBestIndex)(sqlite3_vtab *pVTab, sqlite3_index_info*);
        /// </code>
        /// <para>
        /// The SQLite core communicates with the xBestIndex method by filling
        /// in certain fields of the sqlite3_index_info structure and passing a
        /// pointer to that structure into xBestIndex as the second parameter.
        /// The xBestIndex method fills out other fields of this structure
        /// which forms the reply. The sqlite3_index_info structure looks like
        /// this:
        /// </para>
        /// <code>
        ///  struct sqlite3_index_info {
        ///    /* Inputs */
        ///    const int nConstraint;   /* Number of entries in aConstraint */
        ///    const struct sqlite3_index_constraint {
        ///       int iColumn;          /* Column on left-hand side of
        ///                              * constraint */
        ///       unsigned char op;     /* Constraint operator */
        ///       unsigned char usable; /* True if this constraint is usable */
        ///       int iTermOffset;      /* Used internally - xBestIndex should
        ///                              * ignore */
        ///    } *const aConstraint;    /* Table of WHERE clause constraints */
        ///    const int nOrderBy;      /* Number of terms in the ORDER BY
        ///                              * clause */
        ///    const struct sqlite3_index_orderby {
        ///       int iColumn;          /* Column number */
        ///       unsigned char desc;   /* True for DESC.  False for ASC. */
        ///    } *const aOrderBy;       /* The ORDER BY clause */
        ///    /* Outputs */
        ///    struct sqlite3_index_constraint_usage {
        ///      int argvIndex;         /* if greater than zero, constraint is
        ///                              * part of argv to xFilter */
        ///      unsigned char omit;    /* Do not code a test for this
        ///                              * constraint */
        ///    } *const aConstraintUsage;
        ///    int idxNum;              /* Number used to identify the index */
        ///    char *idxStr;            /* String, possibly obtained from
        ///                              * sqlite3_malloc() */
        ///    int needToFreeIdxStr;    /* Free idxStr using sqlite3_free() if
        ///                              * true */
        ///    int orderByConsumed;     /* True if output is already ordered */
        ///    double estimatedCost;    /* Estimated cost of using this index */
        ///  };
        /// </code>
        /// <para>
        /// In addition, there are some defined constants:
        /// </para>
        /// <code>
        ///  #define SQLITE_INDEX_CONSTRAINT_EQ    2
        ///  #define SQLITE_INDEX_CONSTRAINT_GT    4
        ///  #define SQLITE_INDEX_CONSTRAINT_LE    8
        ///  #define SQLITE_INDEX_CONSTRAINT_LT    16
        ///  #define SQLITE_INDEX_CONSTRAINT_GE    32
        ///  #define SQLITE_INDEX_CONSTRAINT_MATCH 64
        /// </code>
        /// <para>
        /// The SQLite core calls the xBestIndex method when it is compiling a
        /// query that involves a virtual table. In other words, SQLite calls
        /// this method when it is running sqlite3_prepare() or the equivalent.
        /// By calling this method, the SQLite core is saying to the virtual
        /// table that it needs to access some subset of the rows in the
        /// virtual table and it wants to know the most efficient way to do
        /// that access. The xBestIndex method replies with information that
        /// the SQLite core can then use to conduct an efficient search of the
        /// virtual table.
        /// </para>
        /// <para>
        /// While compiling a single SQL query, the SQLite core might call
        /// xBestIndex multiple times with different settings in
        /// sqlite3_index_info. The SQLite core will then select the
        /// combination that appears to give the best performance.
        /// </para>
        /// <para>
        /// Before calling this method, the SQLite core initializes an instance
        /// of the sqlite3_index_info structure with information about the
        /// query that it is currently trying to process. This information
        /// derives mainly from the WHERE clause and ORDER BY or GROUP BY
        /// clauses of the query, but also from any ON or USING clauses if the
        /// query is a join. The information that the SQLite core provides to
        /// the xBestIndex method is held in the part of the structure that is
        /// marked as "Inputs". The "Outputs" section is initialized to zero.
        /// </para>
        /// <para>
        /// The information in the sqlite3_index_info structure is ephemeral
        /// and may be overwritten or deallocated as soon as the xBestIndex
        /// method returns. If the xBestIndex method needs to remember any part
        /// of the sqlite3_index_info structure, it should make a copy. Care
        /// must be take to store the copy in a place where it will be
        /// deallocated, such as in the idxStr field with needToFreeIdxStr set
        /// to 1.
        /// </para>
        /// <para>
        /// Note that xBestIndex will always be called before xFilter, since
        /// the idxNum and idxStr outputs from xBestIndex are required inputs
        /// to xFilter. However, there is no guarantee that xFilter will be
        /// called following a successful xBestIndex.
        /// </para>
        /// <para>
        /// The xBestIndex method is required for every virtual table
        /// implementation.
        /// </para>
        /// <para>
        /// 2.3.1 Inputs
        /// </para>
        /// <para>
        /// The main thing that the SQLite core is trying to communicate to the
        /// virtual table is the constraints that are available to limit the
        /// number of rows that need to be searched. The aConstraint[] array
        /// contains one entry for each constraint. There will be exactly
        /// nConstraint entries in that array.
        /// </para>
        /// <para>
        /// Each constraint will correspond to a term in the WHERE clause or in
        /// a USING or ON clause that is of the form
        /// </para>
        /// <code>
        ///     column OP EXPR
        /// </code>
        /// <para>
        /// Where "column" is a column in the virtual table, OP is an operator
        /// like "=" or "&lt;", and EXPR is an arbitrary expression. So, for
        /// example, if the WHERE clause contained a term like this:
        /// </para>
        /// <code>
        ///          a = 5
        /// </code>
        /// <para>
        /// Then one of the constraints would be on the "a" column with
        /// operator "=" and an expression of "5". Constraints need not have a
        /// literal representation of the WHERE clause. The query optimizer
        /// might make transformations to the WHERE clause in order to extract
        /// as many constraints as it can. So, for example, if the WHERE clause
        /// contained something like this:
        /// </para>
        /// <code>
        ///          x BETWEEN 10 AND 100 AND 999&gt;y
        /// </code>
        /// <para>
        /// The query optimizer might translate this into three separate
        /// constraints:
        /// </para>
        /// <code>
        ///          x &gt;= 10
        ///          x &lt;= 100
        ///          y &lt; 999
        /// </code>
        /// <para>
        /// For each constraint, the aConstraint[].iColumn field indicates
        /// which column appears on the left-hand side of the constraint. The
        /// first column of the virtual table is column 0. The rowid of the
        /// virtual table is column -1. The aConstraint[].op field indicates
        /// which operator is used. The SQLITE_INDEX_CONSTRAINT_* constants map
        /// integer constants into operator values. Columns occur in the order
        /// they were defined by the call to sqlite3_declare_vtab() in the
        /// xCreate or xConnect method. Hidden columns are counted when
        /// determining the column index.
        /// </para>
        /// <para>
        /// The aConstraint[] array contains information about all constraints
        /// that apply to the virtual table. But some of the constraints might
        /// not be usable because of the way tables are ordered in a join. The
        /// xBestIndex method must therefore only consider constraints that
        /// have an aConstraint[].usable flag which is true.
        /// </para>
        /// <para>
        /// In addition to WHERE clause constraints, the SQLite core also tells
        /// the xBestIndex method about the ORDER BY clause. (In an aggregate
        /// query, the SQLite core might put in GROUP BY clause information in
        /// place of the ORDER BY clause information, but this fact should not
        /// make any difference to the xBestIndex method.) If all terms of the
        /// ORDER BY clause are columns in the virtual table, then nOrderBy
        /// will be the number of terms in the ORDER BY clause and the
        /// aOrderBy[] array will identify the column for each term in the
        /// order by clause and whether or not that column is ASC or DESC.
        /// </para>
        /// <para>
        /// 2.3.2 Outputs
        /// </para>
        /// <para>
        /// Given all of the information above, the job of the xBestIndex
        /// method it to figure out the best way to search the virtual table.
        /// </para>
        /// <para>
        /// The xBestIndex method fills the idxNum and idxStr fields with
        /// information that communicates an indexing strategy to the xFilter
        /// method. The information in idxNum and idxStr is arbitrary as far as
        /// the SQLite core is concerned. The SQLite core just copies the
        /// information through to the xFilter method. Any desired meaning can
        /// be assigned to idxNum and idxStr as long as xBestIndex and xFilter
        /// agree on what that meaning is.
        /// </para>
        /// <para>
        /// The idxStr value may be a string obtained from an SQLite memory
        /// allocation function such as sqlite3_mprintf(). If this is the case,
        /// then the needToFreeIdxStr flag must be set to true so that the
        /// SQLite core will know to call sqlite3_free() on that string when it
        /// has finished with it, and thus avoid a memory leak.
        /// </para>
        /// <para>
        /// If the virtual table will output rows in the order specified by the
        /// ORDER BY clause, then the orderByConsumed flag may be set to true.
        /// If the output is not automatically in the correct order then
        /// orderByConsumed must be left in its default false setting. This
        /// will indicate to the SQLite core that it will need to do a separate
        /// sorting pass over the data after it comes out of the virtual table.
        /// </para>
        /// <para>
        /// The estimatedCost field should be set to the estimated number of
        /// disk access operations required to execute this query against the
        /// virtual table. The SQLite core will often call xBestIndex multiple
        /// times with different constraints, obtain multiple cost estimates,
        /// then choose the query plan that gives the lowest estimate.
        /// </para>
        /// <para>
        /// The aConstraintUsage[] array contains one element for each of the
        /// nConstraint constraints in the inputs section of the
        /// sqlite3_index_info structure. The aConstraintUsage[] array is used
        /// by xBestIndex to tell the core how it is using the constraints.
        /// </para>
        /// <para>
        /// The xBestIndex method may set aConstraintUsage[].argvIndex entries
        /// to values greater than one. Exactly one entry should be set to 1,
        /// another to 2, another to 3, and so forth up to as many or as few as
        /// the xBestIndex method wants. The EXPR of the corresponding
        /// constraints will then be passed in as the argv[] parameters to
        /// xFilter.
        /// </para>
        /// <para>
        /// For example, if the aConstraint[3].argvIndex is set to 1, then when
        /// xFilter is called, the argv[0] passed to xFilter will have the EXPR
        /// value of the aConstraint[3] constraint.
        /// </para>
        /// <para>
        /// By default, the SQLite core double checks all constraints on each
        /// row of the virtual table that it receives. If such a check is
        /// redundant, the xBestFilter method can suppress that double-check by
        /// setting aConstraintUsage[].omit.
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="pIndex">
        /// The native pointer to the sqlite3_index_info structure.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xBestIndex(
            IntPtr pVtab,
            IntPtr pIndex
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// This method releases a connection to a virtual table. Only the
        /// sqlite3_vtab object is destroyed. The virtual table is not
        /// destroyed and any backing store associated with the virtual table
        /// persists. This method undoes the work of xConnect.
        /// </para>
        /// <para>
        /// This method is a destructor for a connection to the virtual table.
        /// Contrast this method with xDestroy. The xDestroy is a destructor
        /// for the entire virtual table.
        /// </para>
        /// <para>
        /// The xDisconnect method is required for every virtual table
        /// implementation, though it is acceptable for the xDisconnect and
        /// xDestroy methods to be the same function if that makes sense for
        /// the particular virtual table.
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xDisconnect(
            IntPtr pVtab
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// This method releases a connection to a virtual table, just like the
        /// xDisconnect method, and it also destroys the underlying table
        /// implementation. This method undoes the work of xCreate.
        /// </para>
        /// <para>
        /// The xDisconnect method is called whenever a database connection
        /// that uses a virtual table is closed. The xDestroy method is only
        /// called when a DROP TABLE statement is executed against the virtual
        /// table.
        /// </para>
        /// <para>
        /// The xDestroy method is required for every virtual table
        /// implementation, though it is acceptable for the xDisconnect and
        /// xDestroy methods to be the same function if that makes sense for
        /// the particular virtual table.
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xDestroy(
            IntPtr pVtab
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// The xOpen method creates a new cursor used for accessing (read
        /// and/or writing) a virtual table. A successful invocation of this
        /// method will allocate the memory for the sqlite3_vtab_cursor (or a
        /// subclass), initialize the new object, and make *ppCursor point to
        /// the new object. The successful call then returns SQLITE_OK.
        /// </para>
        /// <para>
        /// For every successful call to this method, the SQLite core will
        /// later invoke the xClose method to destroy the allocated cursor.
        /// </para>
        /// <para>
        /// The xOpen method need not initialize the pVtab field of the
        /// sqlite3_vtab_cursor structure. The SQLite core will take care of
        /// that chore automatically.
        /// </para>
        /// <para>
        /// A virtual table implementation must be able to support an arbitrary
        /// number of simultaneously open cursors.
        /// </para>
        /// <para>
        /// When initially opened, the cursor is in an undefined state. The
        /// SQLite core will invoke the xFilter method on the cursor prior to
        /// any attempt to position or read from the cursor.
        /// </para>
        /// <para>
        /// The xOpen method is required for every virtual table
        /// implementation.
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="pCursor">
        /// Upon success, this parameter must be modified to point to the newly
        /// created native sqlite3_vtab_cursor derived structure.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xOpen(
            IntPtr pVtab,
            ref IntPtr pCursor
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// The xClose method closes a cursor previously opened by xOpen. The
        /// SQLite core will always call xClose once for each cursor opened
        /// using xOpen.
        /// </para>
        /// <para>
        /// This method must release all resources allocated by the
        /// corresponding xOpen call. The routine will not be called again even
        /// if it returns an error. The SQLite core will not use the
        /// sqlite3_vtab_cursor again after it has been closed.
        /// </para>
        /// <para>
        /// The xClose method is required for every virtual table
        /// implementation.
        /// </para>
        /// </summary>
        /// <param name="pCursor">
        /// The native pointer to the sqlite3_vtab_cursor derived structure.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xClose(
            IntPtr pCursor
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// This method begins a search of a virtual table. The first argument
        /// is a cursor opened by xOpen. The next two argument define a
        /// particular search index previously chosen by xBestIndex. The
        /// specific meanings of idxNum and idxStr are unimportant as long as
        /// xFilter and xBestIndex agree on what that meaning is.
        /// </para>
        /// <para>
        /// The xBestIndex function may have requested the values of certain
        /// expressions using the aConstraintUsage[].argvIndex values of the
        /// sqlite3_index_info structure. Those values are passed to xFilter
        /// using the argc and argv parameters.
        /// </para>
        /// <para>
        /// If the virtual table contains one or more rows that match the
        /// search criteria, then the cursor must be left point at the first
        /// row. Subsequent calls to xEof must return false (zero). If there
        /// are no rows match, then the cursor must be left in a state that
        /// will cause the xEof to return true (non-zero). The SQLite engine
        /// will use the xColumn and xRowid methods to access that row content.
        /// The xNext method will be used to advance to the next row.
        /// </para>
        /// <para>
        /// This method must return SQLITE_OK if successful, or an sqlite error
        /// code if an error occurs.
        /// </para>
        /// <para>
        /// The xFilter method is required for every virtual table
        /// implementation.
        /// </para>
        /// </summary>
        /// <param name="pCursor">
        /// The native pointer to the sqlite3_vtab_cursor derived structure.
        /// </param>
        /// <param name="idxNum">
        /// Number used to help identify the selected index.
        /// </param>
        /// <param name="idxStr">
        /// The native pointer to the UTF-8 encoded string containing the
        /// string used to help identify the selected index.
        /// </param>
        /// <param name="argc">
        /// The number of native pointers to sqlite3_value structures specified
        /// in <paramref name="argv" />.
        /// </param>
        /// <param name="argv">
        /// An array of native pointers to sqlite3_value structures containing
        /// filtering criteria for the selected index.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xFilter(
            IntPtr pCursor,
            int idxNum,
            IntPtr idxStr,
            int argc,
            IntPtr argv
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// The xNext method advances a virtual table cursor to the next row of
        /// a result set initiated by xFilter. If the cursor is already
        /// pointing at the last row when this routine is called, then the
        /// cursor no longer points to valid data and a subsequent call to the
        /// xEof method must return true (non-zero). If the cursor is
        /// successfully advanced to another row of content, then subsequent
        /// calls to xEof must return false (zero).
        /// </para>
        /// <para>
        /// This method must return SQLITE_OK if successful, or an sqlite error
        /// code if an error occurs.
        /// </para>
        /// <para>
        /// The xNext method is required for every virtual table
        /// implementation.
        /// </para>
        /// </summary>
        /// <param name="pCursor">
        /// The native pointer to the sqlite3_vtab_cursor derived structure.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xNext(
            IntPtr pCursor
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// The xEof method must return false (zero) if the specified cursor
        /// currently points to a valid row of data, or true (non-zero)
        /// otherwise. This method is called by the SQL engine immediately
        /// after each xFilter and xNext invocation.
        /// </para>
        /// <para>
        /// The xEof method is required for every virtual table implementation.
        /// </para>
        /// </summary>
        /// <param name="pCursor">
        /// The native pointer to the sqlite3_vtab_cursor derived structure.
        /// </param>
        /// <returns>
        /// Non-zero if no more rows are available; zero otherwise.
        /// </returns>
        int xEof(
            IntPtr pCursor
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// The SQLite core invokes this method in order to find the value for
        /// the N-th column of the current row. N is zero-based so the first
        /// column is numbered 0. The xColumn method may return its result back
        /// to SQLite using one of the following interface:
        /// </para>
        /// <code>
        ///     sqlite3_result_blob()
        ///     sqlite3_result_double()
        ///     sqlite3_result_int()
        ///     sqlite3_result_int64()
        ///     sqlite3_result_null()
        ///     sqlite3_result_text()
        ///     sqlite3_result_text16()
        ///     sqlite3_result_text16le()
        ///     sqlite3_result_text16be()
        ///     sqlite3_result_zeroblob()
        /// </code>
        /// <para>
        /// If the xColumn method implementation calls none of the functions
        /// above, then the value of the column defaults to an SQL NULL.
        /// </para>
        /// <para>
        /// To raise an error, the xColumn method should use one of the
        /// result_text() methods to set the error message text, then return an
        /// appropriate error code. The xColumn method must return SQLITE_OK on
        /// success.
        /// </para>
        /// <para>
        /// The xColumn method is required for every virtual table
        /// implementation.
        /// </para>
        /// </summary>
        /// <param name="pCursor">
        /// The native pointer to the sqlite3_vtab_cursor derived structure.
        /// </param>
        /// <param name="pContext">
        /// The native pointer to the sqlite3_context structure to be used
        /// for returning the specified column value to the SQLite core
        /// library.
        /// </param>
        /// <param name="index">
        /// The zero-based index corresponding to the column containing the
        /// value to be returned.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xColumn(
            IntPtr pCursor,
            IntPtr pContext,
            int index
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// A successful invocation of this method will cause *pRowid to be
        /// filled with the rowid of row that the virtual table cursor pCur is
        /// currently pointing at. This method returns SQLITE_OK on success. It
        /// returns an appropriate error code on failure.
        /// </para>
        /// <para>
        /// The xRowid method is required for every virtual table
        /// implementation.
        /// </para>
        /// </summary>
        /// <param name="pCursor">
        /// The native pointer to the sqlite3_vtab_cursor derived structure.
        /// </param>
        /// <param name="rowId">
        /// Upon success, this parameter must be modified to contain the unique
        /// integer row identifier for the current row for the specified cursor.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xRowId(
            IntPtr pCursor,
            ref long rowId
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// All changes to a virtual table are made using the xUpdate method.
        /// This one method can be used to insert, delete, or update.
        /// </para>
        /// <para>
        /// The argc parameter specifies the number of entries in the argv
        /// array. The value of argc will be 1 for a pure delete operation or
        /// N+2 for an insert or replace or update where N is the number of
        /// columns in the table. In the previous sentence, N includes any
        /// hidden columns.
        /// </para>
        /// <para>
        /// Every argv entry will have a non-NULL value in C but may contain
        /// the SQL value NULL. In other words, it is always true that
        /// argv[i]!=0 for i between 0 and argc-1. However, it might be the
        /// case that sqlite3_value_type(argv[i])==SQLITE_NULL.
        /// </para>
        /// <para>
        /// The argv[0] parameter is the rowid of a row in the virtual table
        /// to be deleted. If argv[0] is an SQL NULL, then no deletion occurs.
        /// </para>
        /// <para>
        /// The argv[1] parameter is the rowid of a new row to be inserted into
        /// the virtual table. If argv[1] is an SQL NULL, then the
        /// implementation must choose a rowid for the newly inserted row.
        /// Subsequent argv[] entries contain values of the columns of the
        /// virtual table, in the order that the columns were declared. The
        /// number of columns will match the table declaration that the
        /// xConnect or xCreate method made using the sqlite3_declare_vtab()
        /// call. All hidden columns are included.
        /// </para>
        /// <para>
        /// When doing an insert without a rowid (argc>1, argv[1] is an SQL
        /// NULL), the implementation must set *pRowid to the rowid of the
        /// newly inserted row; this will become the value returned by the
        /// sqlite3_last_insert_rowid() function. Setting this value in all the
        /// other cases is a harmless no-op; the SQLite engine ignores the
        /// *pRowid return value if argc==1 or argv[1] is not an SQL NULL.
        /// </para>
        /// <para>
        /// Each call to xUpdate will fall into one of cases shown below. Note
        /// that references to argv[i] mean the SQL value held within the
        /// argv[i] object, not the argv[i] object itself.
        /// </para>
        /// <code>
        ///     argc = 1
        /// </code>
        /// <para>
        ///         The single row with rowid equal to argv[0] is deleted. No
        ///         insert occurs.
        /// </para>
        /// <code>
        ///     argc > 1
        ///     argv[0] = NULL
        /// </code>
        /// <para>
        ///         A new row is inserted with a rowid argv[1] and column
        ///         values in argv[2] and following. If argv[1] is an SQL NULL,
        ///         the a new unique rowid is generated automatically.
        /// </para>
        /// <code>
        ///     argc > 1
        ///     argv[0] ? NULL
        ///     argv[0] = argv[1]
        /// </code>
        /// <para>
        ///         The row with rowid argv[0] is updated with new values in
        ///         argv[2] and following parameters.
        /// </para>
        /// <code>
        ///     argc > 1
        ///     argv[0] ? NULL
        ///     argv[0] ? argv[1]
        /// </code>
        /// <para>
        ///         The row with rowid argv[0] is updated with rowid argv[1]
        ///         and new values in argv[2] and following parameters. This
        ///         will occur when an SQL statement updates a rowid, as in
        ///         the statement:
        /// </para>
        /// <code>
        ///             UPDATE table SET rowid=rowid+1 WHERE ...;
        /// </code>
        /// <para>
        /// The xUpdate method must return SQLITE_OK if and only if it is
        /// successful. If a failure occurs, the xUpdate must return an
        /// appropriate error code. On a failure, the pVTab->zErrMsg element
        /// may optionally be replaced with error message text stored in memory
        /// allocated from SQLite using functions such as sqlite3_mprintf() or
        /// sqlite3_malloc().
        /// </para>
        /// <para>
        /// If the xUpdate method violates some constraint of the virtual table
        /// (including, but not limited to, attempting to store a value of the
        /// wrong datatype, attempting to store a value that is too large or
        /// too small, or attempting to change a read-only value) then the
        /// xUpdate must fail with an appropriate error code.
        /// </para>
        /// <para>
        /// There might be one or more sqlite3_vtab_cursor objects open and in
        /// use on the virtual table instance and perhaps even on the row of
        /// the virtual table when the xUpdate method is invoked. The
        /// implementation of xUpdate must be prepared for attempts to delete
        /// or modify rows of the table out from other existing cursors. If the
        /// virtual table cannot accommodate such changes, the xUpdate method
        /// must return an error code.
        /// </para>
        /// <para>
        /// The xUpdate method is optional. If the xUpdate pointer in the
        /// sqlite3_module for a virtual table is a NULL pointer, then the
        /// virtual table is read-only.
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="argc">
        /// The number of new or modified column values contained in
        /// <paramref name="argv" />.
        /// </param>
        /// <param name="argv">
        /// The array of native pointers to sqlite3_value structures containing
        /// the new or modified column values, if any.
        /// </param>
        /// <param name="rowId">
        /// Upon success, this parameter must be modified to contain the unique
        /// integer row identifier for the row that was inserted, if any.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xUpdate(
            IntPtr pVtab,
            int argc,
            IntPtr argv,
            ref long rowId
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// This method begins a transaction on a virtual table. This is method
        /// is optional. The xBegin pointer of sqlite3_module may be NULL.
        /// </para>
        /// <para>
        /// This method is always followed by one call to either the xCommit or
        /// xRollback method. Virtual table transactions do not nest, so the
        /// xBegin method will not be invoked more than once on a single
        /// virtual table without an intervening call to either xCommit or
        /// xRollback. Multiple calls to other methods can and likely will
        /// occur in between the xBegin and the corresponding xCommit or
        /// xRollback.
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xBegin(
            IntPtr pVtab
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// This method signals the start of a two-phase commit on a virtual
        /// table. This is method is optional. The xSync pointer of
        /// sqlite3_module may be NULL.
        /// </para>
        /// <para>
        /// This method is only invoked after call to the xBegin method and
        /// prior to an xCommit or xRollback. In order to implement two-phase
        /// commit, the xSync method on all virtual tables is invoked prior to
        /// invoking the xCommit method on any virtual table. If any of the
        /// xSync methods fail, the entire transaction is rolled back.
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xSync(
            IntPtr pVtab
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// This method causes a virtual table transaction to commit. This is
        /// method is optional. The xCommit pointer of sqlite3_module may be
        /// NULL.
        /// </para>
        /// <para>
        /// A call to this method always follows a prior call to xBegin and
        /// xSync.
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xCommit(
            IntPtr pVtab
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// This method causes a virtual table transaction to rollback. This is
        /// method is optional. The xRollback pointer of sqlite3_module may be
        /// NULL.
        /// </para>
        /// <para>
        /// A call to this method always follows a prior call to xBegin.
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xRollback(
            IntPtr pVtab
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// This method provides notification that the virtual table
        /// implementation that the virtual table will be given a new name. If
        /// this method returns SQLITE_OK then SQLite renames the table. If
        /// this method returns an error code then the renaming is prevented.
        /// </para>
        /// <para>
        /// The xRename method is required for every virtual table
        /// implementation.
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="nArg">
        /// The number of arguments to the function being sought.
        /// </param>
        /// <param name="zName">
        /// The name of the function being sought.
        /// </param>
        /// <param name="callback">
        /// Upon success, this parameter must be modified to contain the
        /// delegate responsible for implementing the specified function.
        /// </param>
        /// <param name="pClientData">
        /// Upon success, this parameter must be modified to contain the
        /// native user-data pointer associated with
        /// <paramref name="callback" />.
        /// </param>
        /// <returns>
        /// Non-zero if the specified function was found; zero otherwise.
        /// </returns>
        int xFindFunction(
            IntPtr pVtab,
            int nArg,
            IntPtr zName,
            ref SQLiteCallback callback,
            ref IntPtr pClientData
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// This method provides notification that the virtual table
        /// implementation that the virtual table will be given a new name. If
        /// this method returns SQLITE_OK then SQLite renames the table. If
        /// this method returns an error code then the renaming is prevented.
        /// </para>
        /// <para>
        /// The xRename method is required for every virtual table
        /// implementation.
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="zNew">
        /// The native pointer to the UTF-8 encoded string containing the new
        /// name for the virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xRename(
            IntPtr pVtab,
            IntPtr zNew
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// These methods provide the virtual table implementation an
        /// opportunity to implement nested transactions. They are always
        /// optional and will only be called in SQLite version 3.7.7 and later.
        /// </para>
        /// <para>
        /// When xSavepoint(X,N) is invoked, that is a signal to the virtual
        /// table X that it should save its current state as savepoint N. A
        /// subsequent call to xRollbackTo(X,R) means that the state of the
        /// virtual table should return to what it was when xSavepoint(X,R) was
        /// last called. The call to xRollbackTo(X,R) will invalidate all
        /// savepoints with N>R; none of the invalided savepoints will be
        /// rolled back or released without first being reinitialized by a call
        /// to xSavepoint(). A call to xRelease(X,M) invalidates all savepoints
        /// where N>=M.
        /// </para>
        /// <para>
        /// None of the xSavepoint(), xRelease(), or xRollbackTo() methods will
        /// ever be called except in between calls to xBegin() and either
        /// xCommit() or xRollback().
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="iSavepoint">
        /// This is an integer identifier under which the the current state of
        /// the virtual table should be saved.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xSavepoint(
            IntPtr pVtab,
            int iSavepoint
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// These methods provide the virtual table implementation an
        /// opportunity to implement nested transactions. They are always
        /// optional and will only be called in SQLite version 3.7.7 and later.
        /// </para>
        /// <para>
        /// When xSavepoint(X,N) is invoked, that is a signal to the virtual
        /// table X that it should save its current state as savepoint N. A
        /// subsequent call to xRollbackTo(X,R) means that the state of the
        /// virtual table should return to what it was when xSavepoint(X,R) was
        /// last called. The call to xRollbackTo(X,R) will invalidate all
        /// savepoints with N>R; none of the invalided savepoints will be
        /// rolled back or released without first being reinitialized by a call
        /// to xSavepoint(). A call to xRelease(X,M) invalidates all savepoints
        /// where N>=M.
        /// </para>
        /// <para>
        /// None of the xSavepoint(), xRelease(), or xRollbackTo() methods will
        /// ever be called except in between calls to xBegin() and either
        /// xCommit() or xRollback().
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="iSavepoint">
        /// This is an integer used to indicate that any saved states with an
        /// identifier greater than or equal to this should be deleted by the
        /// virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xRelease(
            IntPtr pVtab,
            int iSavepoint
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// <para>
        /// These methods provide the virtual table implementation an
        /// opportunity to implement nested transactions. They are always
        /// optional and will only be called in SQLite version 3.7.7 and later.
        /// </para>
        /// <para>
        /// When xSavepoint(X,N) is invoked, that is a signal to the virtual
        /// table X that it should save its current state as savepoint N. A
        /// subsequent call to xRollbackTo(X,R) means that the state of the
        /// virtual table should return to what it was when xSavepoint(X,R) was
        /// last called. The call to xRollbackTo(X,R) will invalidate all
        /// savepoints with N>R; none of the invalided savepoints will be
        /// rolled back or released without first being reinitialized by a call
        /// to xSavepoint(). A call to xRelease(X,M) invalidates all savepoints
        /// where N>=M.
        /// </para>
        /// <para>
        /// None of the xSavepoint(), xRelease(), or xRollbackTo() methods will
        /// ever be called except in between calls to xBegin() and either
        /// xCommit() or xRollback().
        /// </para>
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="iSavepoint">
        /// This is an integer identifier used to specify a specific saved
        /// state for the virtual table for it to restore itself back to, which
        /// should also have the effect of deleting all saved states with an
        /// integer identifier greater than this one.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode xRollbackTo(
            IntPtr pVtab,
            int iSavepoint
            );
    }
    #endregion
}