Snapshot checkpointing #710
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Codecov ReportAttention: Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## master #710 +/- ##
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- Coverage 85.74% 81.10% -4.65%
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Files 197 197
Lines 29040 29048 +8
Branches 4084 4059 -25
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- Hits 24901 23558 -1343
+ Misses 3915 3844 -71
- Partials 224 1646 +1422 ☔ View full report in Codecov by Sentry. |
cole-miller
approved these changes
Oct 7, 2024
src/vfs.c
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| } else if (sqlite3_stricmp(left, "wal_checkpoint") == 0 | ||
| || (sqlite3_stricmp(left, "wal_autocheckpoint") == 0 && right)) { | ||
| fnctl[0] = sqlite3_mprintf("custom checkpoint not allowed"); | ||
| return SQLITE_IOERR; |
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+1, thanks for thinking of this and adding it.
Signed-off-by: Cole Miller <[email protected]>
Signed-off-by: Cole Miller <[email protected]>
Signed-off-by: Cole Miller <[email protected]>
Signed-off-by: Cole Miller <[email protected]>
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This PR aims at reducing the amount of memory required for a snapshot and removing entirely page allocation from it.
The main idea is not to save the WAL during a snapshot as it is not necessary to do so. Instead, we can apply pages in the WAL to the database being saved. This means that the snapshotting logic will not allocate memory for pages, but just for the buffer list and the headers.
The saving in terms of memory and write size is in the order of
0 - 4MiB(unless a very big transaction happened) as the current implementation has a threshold of 1000 pages in the WAL before trying to checkpoint.While the gain is quite small in absolute terms, it can become important when the size of the database is small, which seems to be likely.