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Fix a couple of bugs with wal_log_hints.

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1. Replay of the WAL record for setting a bit in the visibility map
contained an assertion that a full-page image of that record type can only
occur with checksums enabled. But it can also happen with wal_log_hints, so
remove the assertion. Unlike checksums, wal_log_hints can be changed on the
fly, so it would be complicated to figure out if it was enabled at the time
that the WAL record was generated.

2. wal_log_hints has the same effect on the locking needed to read the LSN
of a page as data checksums. BufferGetLSNAtomic() didn't get the memo.

Backpatch to 9.4, where wal_log_hints was added.
This commit is contained in:
Heikki Linnakangas
2015-06-26 12:38:24 +03:00
parent 8364510a46
commit b6c4b58ac5
2 changed files with 8 additions and 9 deletions
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15
src/backend/access/heap/heapam.c
View File

@ -7413,12 +7413,11 @@ heap_xlog_visible(XLogRecPtr lsn, XLogRecord *record)
ResolveRecoveryConflictWithSnapshot(xlrec->cutoff_xid, xlrec->node);
/*
* If heap block was backed up, restore it. This can only happen with
* checksums enabled.
* If heap block was backed up, restore it. (This can only happen with
* checksums or wal_log_hints enabled).
*/
if (record->xl_info & XLR_BKP_BLOCK(1))
{
Assert(DataChecksumsEnabled());
(void) RestoreBackupBlock(lsn, record, 1, false, false);
}
else
@ -7441,11 +7440,11 @@ heap_xlog_visible(XLogRecPtr lsn, XLogRecord *record)
/*
* We don't bump the LSN of the heap page when setting the
* visibility map bit (unless checksums are 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 we're not inspecting the existing page contents in any
* way, we don't care.
* visibility map bit (unless checksums or wal_log_hints 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 we're not inspecting the existing page
* contents in any way, we don't care.
*
* However, all operations that clear the visibility map bit *do*
* bump the LSN, and those operations will only be replayed if the

2
src/backend/storage/buffer/bufmgr.c
View File

@ -2125,7 +2125,7 @@ BufferGetLSNAtomic(Buffer buffer)
/*
* If we don't need locking for correctness, fastpath out.
*/
if (!DataChecksumsEnabled() || BufferIsLocal(buffer))
if (!XLogHintBitIsNeeded() || BufferIsLocal(buffer))
return PageGetLSN(page);
/* Make sure we've got a real buffer, and that we hold a pin on it. */