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Overview
Comment: | Add details to the page_size pragma, including specification of the page size selection algorithm. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
bc47f60abdfb2e86b7c8b7f40231833e |
User & Date: | drh 2008-04-29 13:10:56.000 |
Context
2008-04-29
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13:18 | Use SQLITE_DEFAULT_PAGE_SIZE instead of 1024 in the page size algorithm. (check-in: c4bd8f4f26 user: drh tags: trunk) | |
13:10 | Add details to the page_size pragma, including specification of the page size selection algorithm. (check-in: bc47f60abd user: drh tags: trunk) | |
2008-04-27
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17:51 | Updates to the SQL language documentation with many added hyperlink targets. (check-in: f060763119 user: drh tags: trunk) | |
Changes
Changes to pages/pragma.in.
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371 372 373 374 375 376 377 | be changed. All other databases use the normal locking mode by default and are affected by this pragma.</p> </li> <tcl>Subsection page_size</tcl> <li><p><b>PRAGMA page_size; <br>PRAGMA page_size = </b><i>bytes</i><b>;</b></p> | | | | < > > > > > > > > > > > > > > > > > > > > > > > > > > > > > | 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 | be changed. All other databases use the normal locking mode by default and are affected by this pragma.</p> </li> <tcl>Subsection page_size</tcl> <li><p><b>PRAGMA page_size; <br>PRAGMA page_size = </b><i>bytes</i><b>;</b></p> <p>Query or set the page size of the database. The page size may only be set if the database has not yet been created. The page size must be a power of two greater than or equal to 512 and less than or equal to [SQLITE_MAX_PAGE_SIZE]. The maximum value for [SQLITE_MAX_PAGE_SIZE] is 32768. </p> <p>When a new database is created, SQLite assigned a default page size based on information received from the xSectorSize and xDeviceCharacteristics methods of the [sqlite3_io_methods] object of the newly created database file. The page_size pragma will only cause an immediate change in the page size if it is issued while the database is still empty, prior to the first CREATE TABLE statement. As of [version 3.5.8], if the page_size pragma is used to specify a new page size just prior to running the [VACUUM] command then [VACUUM] will change the page size to the new value.</p> <p>If SQLite is compiled with the SQLITE_ENABLE_ATOMIC_WRITE option, then the default page size is chosen to be the largest page size less than or equal to SQLITE_MAX_DEFAULT_PAGE_SIZE for which atomic write is enabled according to the xDeviceCharacteristics method of the [sqlite3_io_methods] object for the database file. If the SQLITE_ENABLE_ATOMIC_WRITE option is disabled or if xDeviceCharacteristics reports no suitable atomic write page sizes, then the default page size is the larger of 1024 and the sector size as reported by the xSectorSize method of the [sqlite3_io_methods] object, but not more than SQLITE_MAX_DEFAULT_PAGE_SIZE. The default configuration for SQLite running on workstations is for atomic write to be disabled, for the maximum page size to be set to 32768, and for the maximum default page size to be set to 8192. The default xSectorSize method on workstation implementations always reports a sector size of 512 bytes. Hence, the default page size chosen by SQLite is usually 1024 bytes.</p> </li> <tcl>Subsection max_page_count</tcl> <li><p><b>PRAGMA max_page_count; <br>PRAGMA max_page_count = </b><i>N</i><b>;</b></p> <p>Query or set the maximum number of pages in the database file. Both forms of the pragma return the maximum page count. The second |
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