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| author | Jeff Davis <jdavis@postgresql.org> | 2022-11-10 14:46:30 -0800 |
|---|---|---|
| committer | Jeff Davis <jdavis@postgresql.org> | 2022-11-11 12:46:11 -0800 |
| commit | 7bf713dd2d0739fbcd4103971ed69c17ebe677ea (patch) | |
| tree | ad26400f8157b25cbe7a1392f0dc7d17451a16e7 | |
| parent | 9c1a4fc891646110fe9b306fe4103f052504d6d9 (diff) | |
| download | postgresql-7bf713dd2d0739fbcd4103971ed69c17ebe677ea.tar.gz postgresql-7bf713dd2d0739fbcd4103971ed69c17ebe677ea.zip | |
Fix theoretical torn page hazard.
The original report was concerned with a possible inconsistency
between the heap and the visibility map, which I was unable to
confirm. The concern has been retracted.
However, there did seem to be a torn page hazard when using
checksums. By not setting the heap page LSN during redo, the
protections of minRecoveryPoint were bypassed. Fixed, along with a
misleading comment.
It may have been impossible to hit this problem in practice, because
it would require a page tear between the checksum and the flags, so I
am marking this as a theoretical risk. But, as discussed, it did
violate expectations about the page LSN, so it may have other
consequences.
Backpatch to all supported versions.
Reported-by: Konstantin Knizhnik
Reviewed-by: Konstantin Knizhnik
Discussion: https://postgr.es/m/fed17dac-8cb8-4f5b-d462-1bb4908c029e@garret.ru
Backpatch-through: 11
| -rw-r--r-- | src/backend/access/heap/heapam.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index 23c4b4f9011..c74fbd01049 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -8823,8 +8823,7 @@ heap_xlog_visible(XLogReaderState *record) /* * We don't bump the LSN of the heap page when setting the visibility * map bit (unless checksums or wal_hint_bits is enabled, in which - * case we must), because that would generate an unworkable volume of - * full-page writes. This exposes us to torn page hazards, but since + * case we must). This exposes us to torn page hazards, but since * we're not inspecting the existing page contents in any way, we * don't care. * @@ -8838,6 +8837,9 @@ heap_xlog_visible(XLogReaderState *record) PageSetAllVisible(page); + if (XLogHintBitIsNeeded()) + PageSetLSN(page, lsn); + MarkBufferDirty(buffer); } else if (action == BLK_RESTORED) |