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Overview
Comment: | Pickup the SQLite core library 3.14 doc changes from upstream. |
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Downloads: | Tarball | ZIP archive |
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70455e449be2e7811ede5d1e54eff001 |
User & Date: | mistachkin 2016-08-09 00:02:18.409 |
Context
2016-08-09
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00:20 | Pickup the 'vtab.html' doc fix from upstream. check-in: 006a35fb5e user: mistachkin tags: trunk | |
00:02 | Pickup the SQLite core library 3.14 doc changes from upstream. check-in: 70455e449b user: mistachkin tags: trunk | |
2016-08-08
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22:47 | Update SQLite core library to the 3.14 release. check-in: e7806a71e7 user: mistachkin tags: trunk | |
Changes
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544 545 546 547 548 549 550 551 552 553 | <h3>The IN and NOT IN operators</h3> <p>The IN and NOT IN operators take a single scalar operand on the left and a vector operand on the right formed by an explicit list of zero or more scalars or by a single subquery. When the right operand of an IN or NOT IN operator is a subquery, the subquery must have a single result column. When the right operand is an empty set, the result of IN is false and the result of NOT IN is true, regardless of the left operand and even if the left operand is NULL. | > > > | | 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 | <h3>The IN and NOT IN operators</h3> <p>The IN and NOT IN operators take a single scalar operand on the left and a vector operand on the right formed by an explicit list of zero or more scalars or by a single subquery. When the right operand of an IN or NOT IN operator is a subquery, the subquery must have a single result column. The "subquery" on the right-hand side of an IN operator can be a table name or <a href="vtab.html#tabfunc2">table-valued function</a> name in which case the subquery is understood to be "(SELECT * FROM <i>name</i>)". When the right operand is an empty set, the result of IN is false and the result of NOT IN is true, regardless of the left operand and even if the left operand is NULL. <p>The result of an IN or NOT IN operator is determined by the following matrix: <center> <table border=1> <tr> <th>Left operand <br>is NULL <th>Right operand <br>contains NULL |
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Changes to Doc/Special/Core/vtab.html.
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133 134 135 136 137 138 139 | </div> </table> <div class=startsearch></div> | > > > > > | > > > > > | | | 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 | </div> </table> <div class=startsearch></div> <div class=fancy> <div style="font-size:2em;text-align:center;color:#044a64"> The Virtual Table Mechanism Of SQLite </div> <div style="font-size:1.5em;margin:1em;color:#044a64"> Table Of Contents</div> <div id=toc> <div style="margin-left:6ex"><a href="#section_1">1. Introduction</a></div><div style="margin-left:12ex"><a href="#section_1_1">1.1. Usage</a></div><div style="margin-left:18ex"><a href="#section_1_1_1">1.1.1. Temporary virtual tables</a></div><div style="margin-left:18ex"><a href="#section_1_1_2">1.1.2. Eponymous virtual tables</a></div><div style="margin-left:18ex"><a href="#section_1_1_3">1.1.3. Eponymous-only virtual tables</a></div><div style="margin-left:12ex"><a href="#section_1_2">1.2. Implementation</a></div><div style="margin-left:12ex"><a href="#section_1_3">1.3. Virtual Tables And Shared Cache</a></div><div style="margin-left:12ex"><a href="#section_1_4">1.4. Creating New Virtual Table Implementations</a></div><div style="margin-left:6ex"><a href="#section_2">2. Virtual Table Methods</a></div><div style="margin-left:12ex"><a href="#section_2_1">2.1. The xCreate Method</a></div><div style="margin-left:18ex"><a href="#section_2_1_1">2.1.1. Hidden columns in virtual tables</a></div><div style="margin-left:18ex"><a href="#section_2_1_2">2.1.2. Table-valued functions</a></div><div style="margin-left:18ex"><a href="#section_2_1_3">2.1.3. WITHOUT ROWID Virtual Tables </a></div><div style="margin-left:12ex"><a href="#section_2_2">2.2. The xConnect Method</a></div><div style="margin-left:12ex"><a href="#section_2_3">2.3. The xBestIndex Method</a></div><div style="margin-left:18ex"><a href="#section_2_3_1">2.3.1. Inputs</a></div><div style="margin-left:18ex"><a href="#section_2_3_2">2.3.2. Outputs</a></div><div style="margin-left:12ex"><a href="#section_2_4">2.4. The xDisconnect Method</a></div><div style="margin-left:12ex"><a href="#section_2_5">2.5. The xDestroy Method</a></div><div style="margin-left:12ex"><a href="#section_2_6">2.6. The xOpen Method</a></div><div style="margin-left:12ex"><a href="#section_2_7">2.7. The xClose Method</a></div><div style="margin-left:12ex"><a href="#section_2_8">2.8. The xEof Method</a></div><div style="margin-left:12ex"><a href="#section_2_9">2.9. The xFilter Method</a></div><div style="margin-left:12ex"><a href="#section_2_10">2.10. The xNext Method</a></div><div style="margin-left:12ex"><a href="#section_2_11">2.11. The xColumn Method</a></div><div style="margin-left:12ex"><a href="#section_2_12">2.12. The xRowid Method</a></div><div style="margin-left:12ex"><a href="#section_2_13">2.13. The xUpdate Method</a></div><div style="margin-left:12ex"><a href="#section_2_14">2.14. The xFindFunction Method</a></div><div style="margin-left:12ex"><a href="#section_2_15">2.15. The xBegin Method</a></div><div style="margin-left:12ex"><a href="#section_2_16">2.16. The xSync Method</a></div><div style="margin-left:12ex"><a href="#section_2_17">2.17. The xCommit Method</a></div><div style="margin-left:12ex"><a href="#section_2_18">2.18. The xRollback Method</a></div><div style="margin-left:12ex"><a href="#section_2_19">2.19. The xRename Method</a></div><div style="margin-left:12ex"><a href="#section_2_20">2.20. The xSavepoint, xRelease, and xRollbackTo Methods</a></div> </div> <div class=startsearch></div> <h1 id="section_1">1. Introduction</h1> <p>A virtual table is an object that is registered with an open SQLite <a href="c3ref/sqlite3.html">database connection</a>. From the perspective of an SQL statement, the virtual table object looks like any other table or view. But behind the scenes, queries and updates on a virtual table invoke callback methods of the virtual table object instead of reading and writing on the database file. <p>The virtual table mechanism allows an application to publish interfaces that are accessible from SQL statements as if they were tables. SQL statements can do almost anything to a virtual table that they can do to a real table, with the following exceptions: |
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186 187 188 189 190 191 192 | (the <a href="dbstat.html">dbstat virtual table</a>) <li> Read and/or write the content of a comma-separated value (CSV) file <li> Access the filesystem of the host computer as if it were a database table <li> Enabling SQL manipulation of data in statistics packages like R </ul> | | > | 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 | (the <a href="dbstat.html">dbstat virtual table</a>) <li> Read and/or write the content of a comma-separated value (CSV) file <li> Access the filesystem of the host computer as if it were a database table <li> Enabling SQL manipulation of data in statistics packages like R </ul> <h2 id="section_1_1">1.1. Usage</h2> <p>A virtual table is created using a <a href="lang_createvtab.html">CREATE VIRTUAL TABLE</a> statement. <p><b><a href="syntax/create-virtual-table-stmt.html">create-virtual-table-stmt:</a></b> <button id='x1475' onclick='hideorshow("x1475","x1476")'>hide</button></p> <blockquote id='x1476'> <img alt="syntax diagram create-virtual-table-stmt" src="images/syntax/create-virtual-table-stmt.gif" /> |
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233 234 235 236 237 238 239 | arguments. <p>Once a virtual table has been created, it can be used like any other table with the exceptions noted above and imposed by specific virtual table implementations. A virtual table is destroyed using the ordinary <a href="lang_droptable.html">DROP TABLE</a> syntax. | | | | 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 | arguments. <p>Once a virtual table has been created, it can be used like any other table with the exceptions noted above and imposed by specific virtual table implementations. A virtual table is destroyed using the ordinary <a href="lang_droptable.html">DROP TABLE</a> syntax. <h3 id="section_1_1_1">1.1.1. Temporary virtual tables</h3> <p>There is no "CREATE TEMP VIRTUAL TABLE" statement. To create a temporary virtual table, add the "temp" schema before the virtual table name. <blockcuqote><pre> CREATE VIRTUAL TABLE <b>temp.</b>tablename USING module(arg1, ...); </pre></blockquote> <a name="epovtab"></a> <h3 id="section_1_1_2">1.1.2. Eponymous virtual tables</h3> <p>Some virtual tables exist automatically in the "main" schema of every database connection in which their module is registered, even without a <a href="lang_createvtab.html">CREATE VIRTUAL TABLE</a> statement. Such virtual tables are called "eponymous virtual tables". To use an eponymous virtual table, simply use the module name as if it were a table. |
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277 278 279 280 281 282 283 | using the <a href="lang_createvtab.html">CREATE VIRTUAL TABLE</a> statement. The <a href="vtab.html#xconnect">xConnect</a> method whenever a database connection attaches to or reparses a schema. When these two methods are the same, that indicates that the virtual table has no persistent state that needs to be created and destroyed. <a name="epoonlyvtab"></a> | | | | 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 | using the <a href="lang_createvtab.html">CREATE VIRTUAL TABLE</a> statement. The <a href="vtab.html#xconnect">xConnect</a> method whenever a database connection attaches to or reparses a schema. When these two methods are the same, that indicates that the virtual table has no persistent state that needs to be created and destroyed. <a name="epoonlyvtab"></a> <h3 id="section_1_1_3">1.1.3. Eponymous-only virtual tables</h3> <p>If the <a href="vtab.html#xcreate">xCreate</a> method is NULL, then <a href="lang_createvtab.html">CREATE VIRTUAL TABLE</a> statements are prohibited for that virtual table, and the virtual table is an "eponymous-only virtual table". Eponymous-only virtual tables are useful as <a href="vtab.html#tabfunc2">table-valued functions</a>. <p> Note that SQLite versions prior to 3.9.0 did not check the xCreate method for NULL before invoking it. So if an eponymous-only virtual table is registered with SQLite version 3.8.11.1 or earlier and a <a href="lang_createvtab.html">CREATE VIRTUAL TABLE</a> command is attempted against that virtual table module, a jump to a NULL pointer will occur, resulting in a crash. <h2 id="section_1_2">1.2. Implementation</h2> <p>Several new C-level objects are used by the virtual table implementation: <blockquote><pre> typedef struct sqlite3_vtab sqlite3_vtab; typedef struct sqlite3_index_info sqlite3_index_info; typedef struct sqlite3_vtab_cursor sqlite3_vtab_cursor; |
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440 441 442 443 444 445 446 | definition might be extended with additional methods and in that case the iVersion value will be increased. <p>The rest of the module structure consists of methods used to implement various features of the virtual table. Details on what each of these methods do are provided in the sequel. | | | | 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 | definition might be extended with additional methods and in that case the iVersion value will be increased. <p>The rest of the module structure consists of methods used to implement various features of the virtual table. Details on what each of these methods do are provided in the sequel. <h2 id="section_1_3">1.3. Virtual Tables And Shared Cache</h2> <p>Prior to SQLite <a href="releaselog/3_6_17.html">version 3.6.17</a>, the virtual table mechanism assumes that each <a href="c3ref/sqlite3.html">database connection</a> kept its own copy of the database schema. Hence, the virtual table mechanism could not be used in a database that has <a href="sharedcache.html">shared cache mode</a> enabled. The <a href="c3ref/create_module.html">sqlite3_create_module()</a> interface would return an error if <a href="sharedcache.html">shared cache mode</a> is enabled. That restriction was relaxed beginning with SQLite <a href="releaselog/3_6_17.html">version 3.6.17</a>. <h2 id="section_1_4">1.4. Creating New Virtual Table Implementations</h2> <p>Follow these steps to create your own virtual table: <p> <ol> <li> Write all necessary methods. <li> Create an instance of the <a href="c3ref/module.html">sqlite3_module</a> structure containing pointers |
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475 476 477 478 479 480 481 | (for testing purposes). You might use one of those as a guide. Locate these test virtual table implementations by searching for "sqlite3_create_module". <p>You might also want to implement your new virtual table as a <a href="c3ref/load_extension.html">loadable extension</a>. | | | | > > > > > > | | 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 | (for testing purposes). You might use one of those as a guide. Locate these test virtual table implementations by searching for "sqlite3_create_module". <p>You might also want to implement your new virtual table as a <a href="c3ref/load_extension.html">loadable extension</a>. <h1 id="section_2">2. Virtual Table Methods</h1> <a name="xcreate"></a> <h2 id="section_2_1">2.1. The xCreate Method</h2> <blockquote><pre> int (*xCreate)(sqlite3 *db, void *pAux, int argc, char **argv, sqlite3_vtab **ppVTab, char **pzErr); </pre></blockquote> <p>The xCreate method is called to create a new instance of a virtual table in response to a <a href="lang_createvtab.html">CREATE VIRTUAL TABLE</a> statement. If the xCreate method is the same pointer as the <a href="vtab.html#xconnect">xConnect</a> method, then the virtual table is an <a href="vtab.html#epovtab">eponymous virtual table</a>. If the xCreate method is omitted (if it is a NULL pointer) then the virtual table is an <a href="vtab.html#epoonlyvtab">eponymous-only virtual table</a>. <p>The db parameter is a pointer to the SQLite <a href="c3ref/sqlite3.html">database connection</a> that is executing the <a href="lang_createvtab.html">CREATE VIRTUAL TABLE</a> statement. The pAux argument is the copy of the client data pointer that was the fourth argument to the <a href="c3ref/create_module.html">sqlite3_create_module()</a> or <a href="c3ref/create_module.html">sqlite3_create_module_v2()</a> call that registered the <a href="c3ref/module.html">virtual table module</a>. 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 |
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565 566 567 568 569 570 571 | If the xCreate method is the exact same pointer as the <a href="vtab.html#xconnect">xConnect</a> method, that indicates that the virtual table does not need to initialize backing store. Such a virtual table can be used as an <a href="vtab.html#epovtab">eponymous virtual table</a> or as a named virtual table using <a href="lang_createvtab.html">CREATE VIRTUAL TABLE</a> or both. <a name="hiddencol"></a> | | | 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 | If the xCreate method is the exact same pointer as the <a href="vtab.html#xconnect">xConnect</a> method, that indicates that the virtual table does not need to initialize backing store. Such a virtual table can be used as an <a href="vtab.html#epovtab">eponymous virtual table</a> or as a named virtual table using <a href="lang_createvtab.html">CREATE VIRTUAL TABLE</a> or both. <a name="hiddencol"></a> <h3 id="section_2_1_1">2.1.1. Hidden columns in virtual tables</h3> <p>If a column datatype contains the special keyword "HIDDEN" (in any combination of upper and lower case letters) then that keyword it is omitted from the column datatype name and the column is marked as a hidden column internally. A hidden column differs from a normal column in three respects: <p> |
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598 599 600 601 602 603 604 | <p>An example use of hidden columns can be seen in the <a href="fts3.html">FTS3</a> virtual table implementation, where every FTS virtual table contains an <a href="fts3.html#hiddencol">FTS hidden column</a> that is used to pass information from the virtual table into <a href="fts3.html#snippet">FTS auxiliary functions</a> and to the <a href="fts3.html#section_3">FTS MATCH</a> operator. <a name="tabfunc2"></a> | | | 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 | <p>An example use of hidden columns can be seen in the <a href="fts3.html">FTS3</a> virtual table implementation, where every FTS virtual table contains an <a href="fts3.html#hiddencol">FTS hidden column</a> that is used to pass information from the virtual table into <a href="fts3.html#snippet">FTS auxiliary functions</a> and to the <a href="fts3.html#section_3">FTS MATCH</a> operator. <a name="tabfunc2"></a> <h3 id="section_2_1_2">2.1.2. Table-valued functions</h3> <p>A <a href="vtab.html">virtual table</a> that contains <a href="vtab.html#hiddencol">hidden columns</a> can be used like a table-valued function in the FROM clause of a <a href="lang_select.html">SELECT</a> statement. The arguments to the table-valued function become constraints on the HIDDEN columns of the virtual table. <p>For example, the "generate_series" extension (located in the |
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641 642 643 644 645 646 647 648 649 650 | <p>Arguments on the virtual table name are matched to <a href="vtab.html#hiddencol">hidden columns</a> in order. The number of arguments can be less than the number of hidden columns, in which case the latter hidden columns are unconstrained. However, an error results if there are more arguments than there are hidden columns in the virtual table. <a name="xconnect"></a> | > > > > > > > > > > > > > > > > > > > > > > > > > | | 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 | <p>Arguments on the virtual table name are matched to <a href="vtab.html#hiddencol">hidden columns</a> in order. The number of arguments can be less than the number of hidden columns, in which case the latter hidden columns are unconstrained. However, an error results if there are more arguments than there are hidden columns in the virtual table. <a name="worid"></a> <h3 id="section_2_1_3">2.1.3. WITHOUT ROWID Virtual Tables </h3> <p>Beginning with SQLite <a href="releaselog/3_14.html">version 3.14.0</a>, the CREATE TABLE statement that is passed into <a href="c3ref/declare_vtab.html">sqlite3_declare_vtab()</a> may contain a <a href="withoutrowid.html">WITHOUT ROWID</a> clause. This is useful for cases where the virtual table rows cannot easily be mapped into unique integers. A CREATE TABLE statement that includes WITHOUT ROWID must define one or more columns as the PRIMARY KEY. Every column of the PRIMARY KEY must individually be NOT NULL and all columns for each row must be collectively unique. <p>Note that SQLite does not enforce the PRIMARY KEY for a WITHOUT ROWID virtual table. Enforcement is the responsibility of the underlying virtual table implementation. But SQLite does assume that the PRIMARY KEY constraint is valid - that the identified columns really are UNIQUE and NOT NULL - and it uses that assumption to optimize queries against the virtual table. <p>The rowid column is not accessible on a WITHOUT ROWID virtual table (of course). Furthermore, since the <a href="vtab.html#xupdate">xUpdate</a> method depends on having a valid rowid, the <a href="vtab.html#xupdate">xUpdate</a> method must be NULL for a WITHOUT ROWID virtual table. That in turn means that WITHOUT ROWID virtual tables must be read-only. <a name="xconnect"></a> <h2 id="section_2_2">2.2. The xConnect Method</h2> <blockquote><pre> int (*xConnect)(sqlite3*, void *pAux, int argc, char **argv, sqlite3_vtab **ppVTab, char **pzErr); </pre></blockquote> |
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700 701 702 703 704 705 706 | <p>The xConnect method is required for every virtual table implementation, though the <a href="vtab.html#xcreate">xCreate</a> and xConnect pointers of the <a href="c3ref/module.html">sqlite3_module</a> object may point to the same function if the virtual table does not need to initialize backing store. <a name="xbestindex"></a> | | | 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 | <p>The xConnect method is required for every virtual table implementation, though the <a href="vtab.html#xcreate">xCreate</a> and xConnect pointers of the <a href="c3ref/module.html">sqlite3_module</a> object may point to the same function if the virtual table does not need to initialize backing store. <a name="xbestindex"></a> <h2 id="section_2_3">2.3. The xBestIndex Method</h2> <p>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: <blockquote><pre> int (*xBestIndex)(sqlite3_vtab *pVTab, sqlite3_index_info*); |
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813 814 815 816 817 818 819 | <p>Note that xBestIndex will always be called before <a href="vtab.html#xfilter">xFilter</a>, 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. <p>The xBestIndex method is required for every virtual table implementation. | | | 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 | <p>Note that xBestIndex will always be called before <a href="vtab.html#xfilter">xFilter</a>, 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. <p>The xBestIndex method is required for every virtual table implementation. <h3 id="section_2_3_1">2.3.1. Inputs</h3> <p>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. |
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895 896 897 898 899 900 901 | means that the first column is used. The second lowest bit corresponds to the second column. And so forth. If the most significant bit of colUsed is set, that means that one or more columns other than the first 63 columns are used. If column usage information is needed by the <a href="vtab.html#xfilter">xFilter</a> method, then the required bits must be encoded into either the idxNum or idxStr output fields. | | | 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 | means that the first column is used. The second lowest bit corresponds to the second column. And so forth. If the most significant bit of colUsed is set, that means that one or more columns other than the first 63 columns are used. If column usage information is needed by the <a href="vtab.html#xfilter">xFilter</a> method, then the required bits must be encoded into either the idxNum or idxStr output fields. <h3 id="section_2_3_2">2.3.2. Outputs</h3> <p>Given all of the information above, the job of the xBestIndex method it to figure out the best way to search the virtual table. <p>The xBestIndex method fills the idxNum and idxStr fields with information that communicates an indexing strategy to the <a href="vtab.html#xfilter">xFilter</a> method. The information in idxNum and idxStr is arbitrary as far |
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961 962 963 964 965 966 967 | <p>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. <a name="xdisconnect"></a> | | | 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 | <p>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. <a name="xdisconnect"></a> <h2 id="section_2_4">2.4. The xDisconnect Method</h2> <blockquote><pre> int (*xDisconnect)(sqlite3_vtab *pVTab); </pre></blockquote> <p>This method releases a connection to a virtual table. Only the <a href="c3ref/vtab.html">sqlite3_vtab</a> object is destroyed. |
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984 985 986 987 988 989 990 | <p>The xDisconnect method is required for every virtual table implementation, though it is acceptable for the xDisconnect and <a href="vtab.html#sqlite3_module.xDestroy">xDestroy</a> methods to be the same function if that makes sense for the particular virtual table. <a name="sqlite3_module.xDestroy"></a> | | | | 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 | <p>The xDisconnect method is required for every virtual table implementation, though it is acceptable for the xDisconnect and <a href="vtab.html#sqlite3_module.xDestroy">xDestroy</a> methods to be the same function if that makes sense for the particular virtual table. <a name="sqlite3_module.xDestroy"></a> <h2 id="section_2_5">2.5. The xDestroy Method</h2> <blockquote><pre> int (*xDestroy)(sqlite3_vtab *pVTab); </pre></blockquote> <p>This method releases a connection to a virtual table, just like the <a href="vtab.html#xdisconnect">xDisconnect</a> method, and it also destroys the underlying table implementation. This method undoes the work of <a href="vtab.html#xcreate">xCreate</a>. <p>The <a href="vtab.html#xdisconnect">xDisconnect</a> method is called whenever a database connection that uses a virtual table is closed. The xDestroy method is only called when a <a href="lang_droptable.html">DROP TABLE</a> statement is executed against the virtual table. <p>The xDestroy method is required for every virtual table implementation, though it is acceptable for the <a href="vtab.html#xdisconnect">xDisconnect</a> and xDestroy methods to be the same function if that makes sense for the particular virtual table. <a name="xopen"></a> <h2 id="section_2_6">2.6. The xOpen Method</h2> <blockquote><pre> int (*xOpen)(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor); </pre></blockquote> <p>The xOpen method creates a new cursor used for accessing (read and/or writing) a virtual table. A successful invocation of this method |
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1035 1036 1037 1038 1039 1040 1041 | The SQLite core will invoke the <a href="vtab.html#xfilter">xFilter</a> method on the cursor prior to any attempt to position or read from the cursor. <p>The xOpen method is required for every virtual table implementation. <a name="xclose"></a> | | | | | 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 | The SQLite core will invoke the <a href="vtab.html#xfilter">xFilter</a> method on the cursor prior to any attempt to position or read from the cursor. <p>The xOpen method is required for every virtual table implementation. <a name="xclose"></a> <h2 id="section_2_7">2.7. The xClose Method</h2> <blockquote><pre> int (*xClose)(sqlite3_vtab_cursor*); </pre></blockquote> <p>The xClose method closes a cursor previously opened by <a href="vtab.html#xopen">xOpen</a>. The SQLite core will always call xClose once for each cursor opened using xOpen. <p>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 <a href="c3ref/vtab_cursor.html">sqlite3_vtab_cursor</a> again after it has been closed. <p>The xClose method is required for every virtual table implementation. <a name="xeof"></a> <h2 id="section_2_8">2.8. The xEof Method</h2> <blockquote><pre> int (*xEof)(sqlite3_vtab_cursor*); </pre></blockquote> <p>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 <a href="vtab.html#xfilter">xFilter</a> and <a href="vtab.html#xnext">xNext</a> invocation. <p>The xEof method is required for every virtual table implementation. <a name="xfilter"></a> <h2 id="section_2_9">2.9. The xFilter Method</h2> <blockquote><pre> int (*xFilter)(sqlite3_vtab_cursor*, int idxNum, const char *idxStr, int argc, sqlite3_value **argv); </pre></blockquote> <p>This method begins a search of a virtual table. |
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1105 1106 1107 1108 1109 1110 1111 | <p>This method must return <a href="rescode.html#ok">SQLITE_OK</a> if successful, or an sqlite <a href="rescode.html">error code</a> if an error occurs. <p>The xFilter method is required for every virtual table implementation. <a name="xnext"></a> | | | | 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 | <p>This method must return <a href="rescode.html#ok">SQLITE_OK</a> if successful, or an sqlite <a href="rescode.html">error code</a> if an error occurs. <p>The xFilter method is required for every virtual table implementation. <a name="xnext"></a> <h2 id="section_2_10">2.10. The xNext Method</h2> <blockquote><pre> int (*xNext)(sqlite3_vtab_cursor*); </pre></blockquote> <p>The xNext method advances a <a href="c3ref/vtab_cursor.html">virtual table cursor</a> to the next row of a result set initiated by <a href="vtab.html#xfilter">xFilter</a>. 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 <a href="vtab.html#xeof">xEof</a> method must return true (non-zero). If the cursor is successfully advanced to another row of content, then subsequent calls to <a href="vtab.html#xeof">xEof</a> must return false (zero). <p>This method must return <a href="rescode.html#ok">SQLITE_OK</a> if successful, or an sqlite <a href="rescode.html">error code</a> if an error occurs. <p>The xNext method is required for every virtual table implementation. <a name="xcolumn"></a> <h2 id="section_2_11">2.11. The xColumn Method</h2> <blockquote><pre> int (*xColumn)(sqlite3_vtab_cursor*, sqlite3_context*, int N); </pre></blockquote> <p>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 |
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1164 1165 1166 1167 1168 1169 1170 | methods to set the error message text, then return an appropriate <a href="rescode.html">error code</a>. The xColumn method must return <a href="rescode.html#ok">SQLITE_OK</a> on success. <p>The xColumn method is required for every virtual table implementation. <a name="xrowid"></a> | | | | 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 | methods to set the error message text, then return an appropriate <a href="rescode.html">error code</a>. The xColumn method must return <a href="rescode.html#ok">SQLITE_OK</a> on success. <p>The xColumn method is required for every virtual table implementation. <a name="xrowid"></a> <h2 id="section_2_12">2.12. The xRowid Method</h2> <blockquote><pre> int (*xRowid)(sqlite3_vtab_cursor *pCur, sqlite_int64 *pRowid); </pre></blockquote> <p>A successful invocation of this method will cause *pRowid to be filled with the <a href="lang_createtable.html#rowid">rowid</a> of row that the <a href="c3ref/vtab_cursor.html">virtual table cursor</a> pCur is currently pointing at. This method returns <a href="rescode.html#ok">SQLITE_OK</a> on success. It returns an appropriate <a href="rescode.html">error code</a> on failure.</p> <p>The xRowid method is required for every virtual table implementation. <a name="xupdate"></a> <h2 id="section_2_13">2.13. The xUpdate Method</h2> <blockquote><pre> int (*xUpdate)( sqlite3_vtab *pVTab, int argc, sqlite3_value **argv, sqlite_int64 *pRowid |
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1278 1279 1280 1281 1282 1283 1284 | <p>The xUpdate method is optional. If the xUpdate pointer in the <a href="c3ref/module.html">sqlite3_module</a> for a virtual table is a NULL pointer, then the virtual table is read-only. <a name="xfindfunction"></a> | | | 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 | <p>The xUpdate method is optional. If the xUpdate pointer in the <a href="c3ref/module.html">sqlite3_module</a> for a virtual table is a NULL pointer, then the virtual table is read-only. <a name="xfindfunction"></a> <h2 id="section_2_14">2.14. The xFindFunction Method</h2> <blockquote><pre> int (*xFindFunction)( sqlite3_vtab *pVtab, int nArg, const char *zName, void (**pxFunc)(sqlite3_context*,int,sqlite3_value**), |
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1314 1315 1316 1317 1318 1319 1320 | first argument. <p>The function pointer returned by this routine must be valid for the lifetime of the <a href="c3ref/vtab.html">sqlite3_vtab</a> object given in the first parameter. <a name="xBegin"></a> | | | | | | | | 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 | first argument. <p>The function pointer returned by this routine must be valid for the lifetime of the <a href="c3ref/vtab.html">sqlite3_vtab</a> object given in the first parameter. <a name="xBegin"></a> <h2 id="section_2_15">2.15. The xBegin Method</h2> <blockquote><pre> int (*xBegin)(sqlite3_vtab *pVTab); </pre></blockquote> <p>This method begins a transaction on a virtual table. This is method is optional. The xBegin pointer of <a href="c3ref/module.html">sqlite3_module</a> may be NULL. <p>This method is always followed by one call to either the <a href="vtab.html#xcommit">xCommit</a> or <a href="vtab.html#xrollback">xRollback</a> 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 <a href="vtab.html#xcommit">xCommit</a> or <a href="vtab.html#xrollback">xRollback</a>. Multiple calls to other methods can and likely will occur in between the xBegin and the corresponding <a href="vtab.html#xcommit">xCommit</a> or <a href="vtab.html#xrollback">xRollback</a>. <a name="xsync"></a> <h2 id="section_2_16">2.16. The xSync Method</h2> <blockquote><pre> int (*xSync)(sqlite3_vtab *pVTab); </pre></blockquote> <p>This method signals the start of a two-phase commit on a virtual table. This is method is optional. The xSync pointer of <a href="c3ref/module.html">sqlite3_module</a> may be NULL. <p>This method is only invoked after call to the <a href="vtab.html#xBegin">xBegin</a> method and prior to an <a href="vtab.html#xcommit">xCommit</a> or <a href="vtab.html#xrollback">xRollback</a>. In order to implement two-phase commit, the xSync method on all virtual tables is invoked prior to invoking the <a href="vtab.html#xcommit">xCommit</a> method on any virtual table. If any of the xSync methods fail, the entire transaction is rolled back. <a name="xcommit"></a> <h2 id="section_2_17">2.17. The xCommit Method</h2> <blockquote><pre> int (*xCommit)(sqlite3_vtab *pVTab); </pre></blockquote> <p>This method causes a virtual table transaction to commit. This is method is optional. The xCommit pointer of <a href="c3ref/module.html">sqlite3_module</a> may be NULL. <p>A call to this method always follows a prior call to <a href="vtab.html#xBegin">xBegin</a> and <a href="vtab.html#xsync">xSync</a>. <a name="xrollback"></a> <h2 id="section_2_18">2.18. The xRollback Method</h2> <blockquote><pre> int (*xRollback)(sqlite3_vtab *pVTab); </pre></blockquote> <p>This method causes a virtual table transaction to rollback. This is method is optional. The xRollback pointer of <a href="c3ref/module.html">sqlite3_module</a> may be NULL. <p>A call to this method always follows a prior call to <a href="vtab.html#xBegin">xBegin</a>. <a name="xrename"></a> <h2 id="section_2_19">2.19. The xRename Method</h2> <blockquote><pre> int (*xRename)(sqlite3_vtab *pVtab, const char *zNew); </pre></blockquote> <p>This method provides notification that the virtual table implementation that the virtual table will be given a new name. If this method returns <a href="rescode.html#ok">SQLITE_OK</a> then SQLite renames the table. If this method returns an <a href="rescode.html">error code</a> then the renaming is prevented. <p>The xRename method is required for every virtual table implementation. <a name="xsavepoint"></a> <h2 id="section_2_20">2.20. The xSavepoint, xRelease, and xRollbackTo Methods</h2> <blockquote><pre> int (*xSavepoint)(sqlite3_vtab *pVtab, int); int (*xRelease)(sqlite3_vtab *pVtab, int); int (*xRollbackTo)(sqlite3_vtab *pVtab, int); </pre></blockquote> |
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Changes to Doc/vtab.tcl.
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24 25 26 27 28 29 30 31 32 33 34 35 36 37 | } proc escapeSubSpec { data } { regsub -all -- {&} $data {\\\&} data regsub -all -- {\\(\d+)} $data {\\\\\1} data return $data } proc englishToList { value } { set result [list] foreach element [split $value "\t\n ,"] { if {[string tolower $element] ni [list "" and or]} then { lappend result $element | > > > > > | 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 | } proc escapeSubSpec { data } { regsub -all -- {&} $data {\\\&} data regsub -all -- {\\(\d+)} $data {\\\\\1} data return $data } proc removeSectionId { value } { regsub -- { id="section(?:_\d+)+"} $value "" value return $value } proc englishToList { value } { set result [list] foreach element [split $value "\t\n ,"] { if {[string tolower $element] ni [list "" and or]} then { lappend result $element |
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82 83 84 85 86 87 88 | upvar 1 $indexVarName index upvar 1 $methodsVarName methods array set levels {p 0} set length [llength $lines] while {$index < $length} { | | | 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 | upvar 1 $indexVarName index upvar 1 $methodsVarName methods array set levels {p 0} set length [llength $lines] while {$index < $length} { set line [removeSectionId [lindex $lines $index]] if {[regexp -- $pattern $line]} then { break; # stop on this line for outer loop. } else { set trimLine [string trim $line]; set data "" if {$levels(p) > 0 && [string length $trimLine] == 0} then { |
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187 188 189 190 191 192 193 | set inputData [string map [list \ {<font size="6" color="red">*** DRAFT ***</font>} ""] $inputData] set inputData [string map [list {<p align="center"></p>} ""] $inputData] set lines [split [string map [list \r\n \n] $inputData] \n] | > | | | | 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 | set inputData [string map [list \ {<font size="6" color="red">*** DRAFT ***</font>} ""] $inputData] set inputData [string map [list {<p align="center"></p>} ""] $inputData] set lines [split [string map [list \r\n \n] $inputData] \n] set patterns(method) {^<h2>2\.\d+\. The (.*) Method(?:s)?</h2>$} set prefix " /// " unset -nocomplain methods; set start false for {set index 0} {$index < [llength $lines]} {} { set line [removeSectionId [lindex $lines $index]] if {$start} then { if {[regexp -- $patterns(method) $line dummy capture]} then { foreach method [englishToList $capture] { set methodIndex [expr {$index + 1}] extractMethod \ $method $lines $patterns(method) $prefix methodIndex methods } set index $methodIndex } else { incr index } } elseif {[regexp -- {^<h1>2\. Virtual Table Methods</h1>$} $line]} then { set start true; incr index } else { incr index } } set outputData [string map [list \r\n \n] [readFile $outputFileName]] |
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Changes to System.Data.SQLite/ISQLiteNativeModule.cs.
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18 19 20 21 22 23 24 | /// <para><code> /// int (*xCreate)(sqlite3 *db, void *pAux, /// int argc, char **argv, /// sqlite3_vtab **ppVTab, /// char **pzErr); /// </code></para> /// <para> | | > > > > > > | 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 | /// <para><code> /// int (*xCreate)(sqlite3 *db, void *pAux, /// int argc, char **argv, /// sqlite3_vtab **ppVTab, /// char **pzErr); /// </code></para> /// <para> /// The xCreate method is called to create a new instance of a virtual table /// in response to a CREATE VIRTUAL TABLE statement. /// If the xCreate method is the same pointer as the xConnect method, then the /// virtual table is an eponymous virtual table. /// If the xCreate method is omitted (if it is a NULL pointer) then the virtual /// table is an eponymous-only virtual table. /// </para> /// <para> /// 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. |
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173 174 175 176 177 178 179 180 181 182 183 184 185 186 | /// <para> /// Arguments on the virtual table name are matched to hidden columns /// in order. The number of arguments can be less than the /// number of hidden columns, in which case the latter hidden columns are /// unconstrained. However, an error results if there are more arguments /// than there are hidden columns in the virtual table. /// </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 | > > > > > > > > > > > > > > > > > > > > > > > > | 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 | /// <para> /// Arguments on the virtual table name are matched to hidden columns /// in order. The number of arguments can be less than the /// number of hidden columns, in which case the latter hidden columns are /// unconstrained. However, an error results if there are more arguments /// than there are hidden columns in the virtual table. /// </para> /// <para> /// Beginning with SQLite version 3.14.0, the CREATE TABLE statement that /// is passed into sqlite3_declare_vtab() may contain a WITHOUT ROWID clause. /// This is useful for cases where the virtual table rows /// cannot easily be mapped into unique integers. A CREATE TABLE /// statement that includes WITHOUT ROWID must define one or more columns as /// the PRIMARY KEY. Every column of the PRIMARY KEY must individually be /// NOT NULL and all columns for each row must be collectively unique. /// </para> /// <para> /// Note that SQLite does not enforce the PRIMARY KEY for a WITHOUT ROWID /// virtual table. Enforcement is the responsibility of the underlying /// virtual table implementation. But SQLite does assume that the PRIMARY KEY /// constraint is valid - that the identified columns really are UNIQUE and /// NOT NULL - and it uses that assumption to optimize queries against the /// virtual table. /// </para> /// <para> /// The rowid column is not accessible on a /// WITHOUT ROWID virtual table (of course). Furthermore, since the /// xUpdate method depends on having a valid rowid, the xUpdate method /// must be NULL for a WITHOUT ROWID virtual table. That in turn means that /// WITHOUT ROWID virtual tables must be read-only. /// </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 |
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