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Don't clear btpo_cycleid during _bt_vacuum_one_page.

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When "vacuuming" a single btree page by removing LP_DEAD tuples, we are not
actually within a vacuum operation, but rather in an ordinary insertion
process that could well be running concurrently with a vacuum.  So clearing
the cycleid is incorrect, and could cause the concurrent vacuum to miss
removing tuples that it needs to remove.  This is a longstanding bug
introduced by commit e6284649b9e30372b3990107a082bc7520325676 of
2006-07-25.  I believe it explains Maxim Boguk's recent report of index
corruption, and probably some other previously unexplained reports.

In 9.0 and up this is a one-line fix; before that we need to introduce a
flag to tell _bt_delitems what to do.
This commit is contained in:
Tom Lane 2012-02-21 15:03:36 -05:00
parent 9789c99d01
commit 593a9631a7
1 changed files with 3 additions and 4 deletions
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7
src/backend/access/nbtree/nbtpage.c
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@ -841,11 +841,9 @@ _bt_delitems_delete(Relation rel, Buffer buf,
PageIndexMultiDelete(page, itemnos, nitems);
/*
* We can clear the vacuum cycle ID since this page has certainly been
* processed by the current vacuum scan.
* Unlike _bt_delitems_vacuum, we *must not* clear the vacuum cycle ID,
* because this is not called by VACUUM.
*/
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
opaque->btpo_cycleid = 0;
/*
* Mark the page as not containing any LP_DEAD items. This is not
@ -854,6 +852,7 @@ _bt_delitems_delete(Relation rel, Buffer buf,
* true and it doesn't seem worth an additional page scan to check it.
* Remember that BTP_HAS_GARBAGE is only a hint anyway.
*/
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
opaque->btpo_flags &= ~BTP_HAS_GARBAGE;
MarkBufferDirty(buf);