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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2008-02-11 19:14:45 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2008-02-11 19:14:45 +0000 |
| commit | e2429619b1093b536f4b8324b7fdc54382f04ba3 (patch) | |
| tree | 7d65704b739d534916f5f764e7de49cda23e53cf /src | |
| parent | 4af5e12b59eee56df0f15a3013077f628da60135 (diff) | |
| download | postgresql-e2429619b1093b536f4b8324b7fdc54382f04ba3.tar.gz postgresql-e2429619b1093b536f4b8324b7fdc54382f04ba3.zip | |
Repair VACUUM FULL bug introduced by HOT patch: the original way of
calculating a page's initial free space was fine, and should not have been
"improved" by letting PageGetHeapFreeSpace do it. VACUUM FULL is going to
reclaim LP_DEAD line pointers later, so there is no need for a guard
against the page being too full of line pointers, and having one risks
rejecting pages that are perfectly good move destinations.
This also exposed a second bug, which is that the empty_end_pages logic
assumed that any page with no live tuples would get entered into the
fraged_pages list automatically (by virtue of having more free space than
the threshold in the do_frag calculation). This assumption certainly
seems risky when a low fillfactor has been chosen, and even without
tunable fillfactor I think it could conceivably fail on a page with many
unused line pointers. So fix the code to force do_frag true when notup
is true, and patch this part of the fix all the way back.
Per report from Tomas Szepe.
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/commands/vacuum.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c index 39d769aaa8a..e9f41eac323 100644 --- a/src/backend/commands/vacuum.c +++ b/src/backend/commands/vacuum.c @@ -13,7 +13,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.317.2.6 2008/01/03 21:24:26 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.317.2.7 2008/02/11 19:14:45 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -1515,12 +1515,18 @@ scan_heap(VRelStats *vacrelstats, Relation onerel, free_space += vacpage->free; /* - * Add the page to fraged_pages if it has a useful amount of free - * space. "Useful" means enough for a minimal-sized tuple. But we - * don't know that accurately near the start of the relation, so add - * pages unconditionally if they have >= BLCKSZ/10 free space. + * Add the page to vacuum_pages if it requires reaping, and add it to + * fraged_pages if it has a useful amount of free space. "Useful" + * means enough for a minimal-sized tuple. But we don't know that + * accurately near the start of the relation, so add pages + * unconditionally if they have >= BLCKSZ/10 free space. Also + * forcibly add pages with no live tuples, to avoid confusing the + * empty_end_pages logic. (In the presence of unreasonably small + * fillfactor, it seems possible that such pages might not pass + * the free-space test, but they had better be in the list anyway.) */ - do_frag = (vacpage->free >= min_tlen || vacpage->free >= BLCKSZ / 10); + do_frag = (vacpage->free >= min_tlen || vacpage->free >= BLCKSZ / 10 || + notup); if (do_reap || do_frag) { @@ -1535,6 +1541,7 @@ scan_heap(VRelStats *vacrelstats, Relation onerel, /* * Include the page in empty_end_pages if it will be empty after * vacuuming; this is to keep us from using it as a move destination. + * Note that such pages are guaranteed to be in fraged_pages. */ if (notup) { |