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Overview
Comment: | Update the wal.html document at the bigwal anchor to reflect improvements to large transactions in WAL mode added to version 3.11.0. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | branch-3.11 |
Files: | files | file ages | folders |
SHA1: |
e273b7fdae64222f64196e80a6d4d8c2 |
User & Date: | drh 2016-03-18 14:56:49.802 |
Context
2016-03-21
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20:02 | Fix the description of the case folding performed by the unicode61 tokenizer in FTS3. (check-in: 37a01760c6 user: drh tags: branch-3.11) | |
2016-03-18
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15:46 | Merge wal.html update from the 3.11.0 branch. (check-in: 147aa03544 user: drh tags: trunk) | |
14:56 | Update the wal.html document at the bigwal anchor to reflect improvements to large transactions in WAL mode added to version 3.11.0. (check-in: e273b7fdae user: drh tags: branch-3.11) | |
2016-03-03
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16:20 | Add hashes to the change log. (check-in: 2fdaab5ed5 user: drh tags: branch-3.11) | |
Changes
Changes to pages/wal.in.
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416 417 418 419 420 421 422 | readers might block while the checkpoint is running. <li><p> <b>Very large write transactions.</b> A checkpoint can only complete when no other transactions are running, which means the WAL file cannot be reset in the middle of a write transaction. So a large change to a large database | | < < < < < < < < < < | | | | < < < < | | < < | 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 | readers might block while the checkpoint is running. <li><p> <b>Very large write transactions.</b> A checkpoint can only complete when no other transactions are running, which means the WAL file cannot be reset in the middle of a write transaction. So a large change to a large database might result in a large WAL file. The WAL file will be checkpointed once the write transaction completes (assuming there are no other readers blocking it) but in the meantime, the file can grow very big. <p>As of SQLite version 3.11.0, the WAL file for a single transaction should be proportional in size to the transaction itself. Pages that are changed by the transaction should only be written into the WAL file once. However, with older versions of SQLite, the same page might be written into the WAL file multiple times if the transaction grows larger than the page cache. </ul> <h2>Implementation Of Shared-Memory For The WAL-Index</h2> <p>The [wal-index] is implemented using an ordinary file that is mmapped for robustness. Early (pre-release) implementations of WAL mode stored the wal-index in volatile shared-memory, such as files created in |
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