From 1f2e2aa4fcd3068e38e6e42f4fd2ec40b8b05d27 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Tue, 6 Jan 2009 14:55:44 +0000 Subject: [PATCH] Fix logic in lazy vacuum to decide if it's worth trying to truncate the heap. If the table was smaller than REL_TRUNCATE_FRACTION (= 16) pages, we always tried to acquire AccessExclusiveLock on it even if there was no empty pages at the end. Report by Simon Riggs. Back-patch all the way to 7.4. --- src/backend/commands/vacuumlazy.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c index 967af2c7297..d9224dc28e5 100644 --- a/src/backend/commands/vacuumlazy.c +++ b/src/backend/commands/vacuumlazy.c @@ -38,7 +38,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.103.2.1 2008/03/24 19:12:58 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.103.2.2 2009/01/06 14:55:44 heikki Exp $ * *------------------------------------------------------------------------- */ @@ -200,8 +200,9 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt, * number of pages. Otherwise, the time taken isn't worth it. */ possibly_freeable = vacrelstats->rel_pages - vacrelstats->nonempty_pages; - if (possibly_freeable >= REL_TRUNCATE_MINIMUM || - possibly_freeable >= vacrelstats->rel_pages / REL_TRUNCATE_FRACTION) + if (possibly_freeable > 0 && + (possibly_freeable >= REL_TRUNCATE_MINIMUM || + possibly_freeable >= vacrelstats->rel_pages / REL_TRUNCATE_FRACTION)) lazy_truncate_heap(onerel, vacrelstats); /* Update shared free space map with final free space info */