From 593a9631a7947ab95903e87e24786d7e469cc988 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Tue, 21 Feb 2012 15:03:36 -0500 Subject: [PATCH] Don't clear btpo_cycleid during _bt_vacuum_one_page. 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. --- src/backend/access/nbtree/nbtpage.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/src/backend/access/nbtree/nbtpage.c b/src/backend/access/nbtree/nbtpage.c index 29a9df027b..c5e147ff43 100644 --- a/src/backend/access/nbtree/nbtpage.c +++ b/src/backend/access/nbtree/nbtpage.c @@ -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);