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Avoid marking buffer dirty when VACUUM has no work to do.

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When wal_level = 'hot_standby' we touched the last page of the
relation during a VACUUM, even if nothing else had happened.
That would alter the LSN of the last block and set the mtime
of the relation file unnecessarily. Noted by Thom Brown.
This commit is contained in:
Simon Riggs 2011-11-18 16:06:53 +00:00
parent f6438f6622
commit c1458cc495
1 changed files with 8 additions and 4 deletions
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12
src/backend/access/nbtree/nbtpage.c
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@ -732,7 +732,7 @@ _bt_page_recyclable(Page page)
* and so must be scanned anyway during replay. We always write a WAL record
* for the last block in the index, whether or not it contained any items
* to be removed. This allows us to scan right up to end of index to
* ensure correct locking.
* ensure correct locking. That is the only time we are called with nitems==0.
*/
void
_bt_delitems_vacuum(Relation rel, Buffer buf,
@ -764,7 +764,8 @@ _bt_delitems_vacuum(Relation rel, Buffer buf,
*/
opaque->btpo_flags &= ~BTP_HAS_GARBAGE;
MarkBufferDirty(buf);
if (nitems > 0)
MarkBufferDirty(buf);
/* XLOG stuff */
if (RelationNeedsWAL(rel))
@ -804,8 +805,11 @@ _bt_delitems_vacuum(Relation rel, Buffer buf,
recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_VACUUM, rdata);
PageSetLSN(page, recptr);
PageSetTLI(page, ThisTimeLineID);
if (nitems > 0)
{
PageSetLSN(page, recptr);
PageSetTLI(page, ThisTimeLineID);
}
}
END_CRIT_SECTION();