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Deduplicate PageIsNew() check in lazy_scan_heap(). 

The recheck isn't needed anymore, as RelationGetBufferForTuple() now
extends the relation with RBM_ZERO_AND_LOCK. Previously we needed to
handle the fact that relation extension extended the relation and then
separately acquired a lock on the page - while expecting that the page
is empty.

Reported-By: Ranier Vilela
Discussion: https://postgr.es/m/CAEudQArA_=J0D5T258xsCY6Xtf6wiH4b=QDPDgVS+WZUN10WDw@mail.gmail.com
This commit is contained in:
Andres Freund 2020-03-30 13:51:12 -07:00
parent 364bdd0b41
commit d4b34f60c5
1 changed files with 11 additions and 21 deletions
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32
src/backend/access/heap/vacuumlazy.c
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@ -1147,8 +1147,6 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
if (PageIsNew(page))
{
bool still_new;
/*
* All-zeroes pages can be left over if either a backend extends
* the relation by a single page, but crashes before the newly
@ -1156,36 +1154,28 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
* the relation (which creates a number of empty pages at the tail
* end of the relation, but enters them into the FSM).
*
* Make sure these pages are in the FSM, to ensure they can be
* reused. Do that by testing if there's any space recorded for
* the page. If not, enter it.
*
* Note we do not enter the page into the visibilitymap. That has
* the downside that we repeatedly visit this page in subsequent
* vacuums, but otherwise we'll never not discover the space on a
* promoted standby. The harm of repeated checking ought to
* normally not be too bad - the space usually should be used at
* some point, otherwise there wouldn't be any regular vacuums.
*
* Make sure these pages are in the FSM, to ensure they can be
* reused. Do that by testing if there's any space recorded for
* the page. If not, enter it. We do so after releasing the lock
* on the heap page, the FSM is approximate, after all.
*/
/*
* Perform checking of FSM after releasing lock, the fsm is
* approximate, after all.
*/
still_new = PageIsNew(page);
UnlockReleaseBuffer(buf);
if (still_new)
empty_pages++;
if (GetRecordedFreeSpace(onerel, blkno) == 0)
{
empty_pages++;
Size freespace;
if (GetRecordedFreeSpace(onerel, blkno) == 0)
{
Size freespace;
freespace = BufferGetPageSize(buf) - SizeOfPageHeaderData;
RecordPageWithFreeSpace(onerel, blkno, freespace);
}
freespace = BufferGetPageSize(buf) - SizeOfPageHeaderData;
RecordPageWithFreeSpace(onerel, blkno, freespace);
}
continue;
}