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Overview
Comment: | Merge changes from the 3.24 branch. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA3-256: |
137b4b6a0fb6f29ad1036a0aca3e4926 |
User & Date: | drh 2018-07-23 11:02:03.745 |
Context
2018-07-23
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11:17 | Merge changes from branch-3.24 (check-in: 777501f7ed user: drh tags: trunk) | |
11:02 | Merge changes from the 3.24 branch. (check-in: 137b4b6a0f user: drh tags: trunk) | |
11:00 | Further changes to the prosupport documentation. (check-in: 00457c34b5 user: drh tags: trunk) | |
10:53 | Changes to information on support packages. (check-in: 5caed7a191 user: drh tags: branch-3.24) | |
Changes
Changes to pages/changes.in.
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60 61 62 63 64 65 66 | <li> Automatically intercepts the raw [EXPLAIN QUERY PLAN] output and reformats it into an ASCII-art graph. <li> Lines that begin with "#" and that are not in the middle of an SQL statement are interpreted as comments. <li> Added the --append option to the ".backup" command. <li> Added the ".dbconfig" command. <p><b>Performance:</b> | > | | | | | > > > | 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 | <li> Automatically intercepts the raw [EXPLAIN QUERY PLAN] output and reformats it into an ASCII-art graph. <li> Lines that begin with "#" and that are not in the middle of an SQL statement are interpreted as comments. <li> Added the --append option to the ".backup" command. <li> Added the ".dbconfig" command. <p><b>Performance:</b> <li> [UPDATE] avoids unnecessary low-level disk writes when the contents of the database file do not actually change. For example, "UPDATE t1 SET x=25 WHERE y=?" generates no extra disk I/O if the value in column x is already 25. Similarly, when doing [UPDATE] on records that span multiple pages, only the subset of pages that actually change are written to disk. This is a low-level performance optimization only and does not affect the behavior of TRIGGERs or other higher level SQL structures. <li> Queries that use ORDER BY and LIMIT now try to avoid computing rows that cannot possibly come in under the LIMIT. This can greatly improve performance of ORDER BY LIMIT queries, especially when the LIMIT is small relative to the number of unrestricted output rows. <li> The [OR optimization] is allowed to proceed even if the OR expression has also been converted into an IN expression. Uses of the OR optimization are now also |
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Changes to pages/compile.in.
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1033 1034 1035 1036 1037 1038 1039 | The default sorting procedure is to gather all information that will ultimately be output into a "record" and pass that complete record to the sorter. But in some cases, for example if some of the output columns consists of large BLOB values, the size of the each record can be large, which means that the sorter has to either use more memory, and/or write more content to temporary storage. <p> | | | | | | 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 1061 1062 1063 1064 | The default sorting procedure is to gather all information that will ultimately be output into a "record" and pass that complete record to the sorter. But in some cases, for example if some of the output columns consists of large BLOB values, the size of the each record can be large, which means that the sorter has to either use more memory, and/or write more content to temporary storage. <p> When SQLITE_ENABLE_SORTER_REFERENCES is enabled, the records passed to the sorter often contain only a [ROWID] value. Such records are much smaller. This means the sorter has much less "payload" to deal with and can run faster. After sorting has occurred, the ROWID is used to look up the output column values in the original table. That requires another search into the table, and could potentially result in a slowdown. Or, it might be a performance win, depending on how large the values are. <p> Even when the SQLITE_ENABLE_SORTER_REFERENCES compile-time option is on, sorter references are still disabled by default. To use sorter references, the application must set a sorter reference size threshold using the [sqlite3_config]([SQLITE_CONFIG_SORTERREF_SIZE]) interface at start-time. <p> Because the SQLite developers do not know whether the SQLITE_ENABLE_SORTER_REFERENCES option will help or hurt performance, it is disabled by default at this time (2018-05-04). It might be enabled by default in some future release, depending on what is learned about its impact on performance. } COMPILE_OPTION {SQLITE_ENABLE_STMT_SCANSTATUS} { This option enables the [sqlite3_stmt_scanstatus()] interface. The [sqlite3_stmt_scanstatus()] interface is normally omitted from the build because it imposes a small performance penalty, even on statements that do not use the feature. |
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Changes to pages/lang.in.
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3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 | <p>In this last example, the phonebook2 entry is only updated if the validDate for the newly inserted value is newer than the entry already in the table. If the table already contains an entry with the same name and a current validDate, then the WHERE clause causes the DO UPDATE to become a no-op. <tcl> ############################################################################## Section {ON CONFLICT clause} conflict {{conflict clause} {ON CONFLICT}} RecursiveBubbleDiagram conflict-clause </tcl> | > > > > | 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 | <p>In this last example, the phonebook2 entry is only updated if the validDate for the newly inserted value is newer than the entry already in the table. If the table already contains an entry with the same name and a current validDate, then the WHERE clause causes the DO UPDATE to become a no-op. <h3>Limitations</h3> <p>UPSERT does not currently work for [virtual tables]. <tcl> ############################################################################## Section {ON CONFLICT clause} conflict {{conflict clause} {ON CONFLICT}} RecursiveBubbleDiagram conflict-clause </tcl> |
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Changes to pages/vtab.in.
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261 262 263 264 265 266 267 | destructor for client data pointer. The module structure is what defines the behavior of a virtual table. The module structure looks like this: <codeblock> struct sqlite3_module { int iVersion; int (*xCreate)(sqlite3*, void *pAux, | | | | 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 | destructor for client data pointer. The module structure is what defines the behavior of a virtual table. The module structure looks like this: <codeblock> struct sqlite3_module { int iVersion; int (*xCreate)(sqlite3*, void *pAux, int argc, char *const*argv, sqlite3_vtab **ppVTab, char **pzErr); int (*xConnect)(sqlite3*, void *pAux, int argc, char *const*argv, sqlite3_vtab **ppVTab, char **pzErr); int (*xBestIndex)(sqlite3_vtab *pVTab, sqlite3_index_info*); int (*xDisconnect)(sqlite3_vtab *pVTab); int (*xDestroy)(sqlite3_vtab *pVTab); int (*xOpen)(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor); int (*xClose)(sqlite3_vtab_cursor*); |
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350 351 352 353 354 355 356 | <h1>Virtual Table Methods</h1> <tcl>hd_fragment xcreate {sqlite3_module.xCreate} {xCreate}</tcl> <h2>The xCreate Method</h2> <codeblock> int (*xCreate)(sqlite3 *db, void *pAux, | | | 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 | <h1>Virtual Table Methods</h1> <tcl>hd_fragment xcreate {sqlite3_module.xCreate} {xCreate}</tcl> <h2>The xCreate Method</h2> <codeblock> int (*xCreate)(sqlite3 *db, void *pAux, int argc, char *const*argv, sqlite3_vtab **ppVTab, char **pzErr); </codeblock> <p>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 |
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549 550 551 552 553 554 555 | <tcl>############################################################# xConnect hd_fragment xconnect {sqlite3_module.xConnect} {xConnect}</tcl> <h2>The xConnect Method</h2> <codeblock> int (*xConnect)(sqlite3*, void *pAux, | | | 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 | <tcl>############################################################# xConnect hd_fragment xconnect {sqlite3_module.xConnect} {xConnect}</tcl> <h2>The xConnect Method</h2> <codeblock> int (*xConnect)(sqlite3*, void *pAux, int argc, char *const*argv, sqlite3_vtab **ppVTab, char **pzErr); </codeblock> <p>The xConnect method is very similar to [xCreate]. It has the same parameters and constructs a new [sqlite3_vtab] structure just like xCreate. |
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