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Fix two bugs in setting the vm bit of empty pages.

Browse Source 
Use a critical section when setting the all-visible flag on an empty page,
and WAL-logging it. log_newpage_buffer() contains an assertion that it
must be called inside a critical section, and it's the right thing to do
when modifying a buffer anyway.

Also, the page should be marked dirty before calling log_newpage_buffer(),
per the comment in log_newpage_buffer() and src/backend/access/transam/README.

Patch by Andres Freund, in response to my report. Backpatch to 9.2, like
the patch that introduced these bugs (a6370fd9).
This commit is contained in:
Heikki Linnakangas 2013-10-23 14:03:54 +03:00
parent 5f1ab46101
commit 83eb54001c
1 changed files with 6 additions and 1 deletions
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7
src/backend/commands/vacuumlazy.c
View File

@ -663,6 +663,11 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
/* empty pages are always all-visible */
if (!PageIsAllVisible(page))
{
START_CRIT_SECTION();
/* mark buffer dirty before writing a WAL record */
MarkBufferDirty(buf);
/*
* It's possible that another backend has extended the heap,
* initialized the page, and then failed to WAL-log the page
@ -682,9 +687,9 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
log_newpage_buffer(buf);
PageSetAllVisible(page);
MarkBufferDirty(buf);
visibilitymap_set(onerel, blkno, buf, InvalidXLogRecPtr,
vmbuffer, InvalidTransactionId);
END_CRIT_SECTION();
}
UnlockReleaseBuffer(buf);