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PD_ALL_VISIBLE flag set - autovacuum ignoring dead tuples 2+ messages / 2 participants [nested] [flat]
* PD_ALL_VISIBLE flag set - autovacuum ignoring dead tuples @ 2011-08-03 14:23 Tom Lanyon <tom+pgsql-admin@oneshoeco.com> 0 siblings, 1 reply; 2+ messages in thread From: Tom Lanyon @ 2011-08-03 14:23 UTC (permalink / raw) To: pgsql-admin I'm seeing a heavy-update TOAST table which is not being effectively autovacuum'd on 8.4.5. The stats collector shows n_dead_tup growing very quickly, and autovacuum runs frequently, but never removes any dead tuples. A manual vacuum does find many dead tuples (90+ % of the table) to remove, and removes them properly. Whilst debugging, I found that there seems to be a large amount of the old 'PD_ALL_VISIBLE incorrectly set...' warnings emitted during the autovacuum run. My immediate assumption was that PD_ALL_VISIBLE is set on the page, and so autovacuum skips it. However, from what I can see in lazy_scan_heap(), all of the clean-up actually happens before we even check the PD_ALL_VISIBLE flag and emit this warning. Can anyone confirm that this is a warning message only, and shouldn't actually cause autovacuum to skip pruning dead tuples? Am I seeing two different or related issues here? Thanks, Tom p.s. I'm aware there was a change to PD_ALL_VISIBLE in 8.4.8 but that was to stop warning on a non-issue, so I don't believe it's the same. ^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: PD_ALL_VISIBLE flag set - autovacuum ignoring dead tuples @ 2011-08-09 15:03 Tom Lane <tgl@sss.pgh.pa.us> parent: Tom Lanyon <tom+pgsql-admin@oneshoeco.com> 0 siblings, 0 replies; 2+ messages in thread From: Tom Lane @ 2011-08-09 15:03 UTC (permalink / raw) To: Tom Lanyon <tom+pgsql-admin@oneshoeco.com>; +Cc: pgsql-admin Tom Lanyon <tom+pgsql-admin@oneshoeco.com> writes: > I'm seeing a heavy-update TOAST table which is not being effectively autovacuum'd on 8.4.5. The stats collector shows n_dead_tup growing very quickly, and autovacuum runs frequently, but never removes any dead tuples. A manual vacuum does find many dead tuples (90+ % of the table) to remove, and removes them properly. Is autovacuum actually running against the toast table? Check the last_autovacuum column in pg_stat_all_tables. If not, and if pg_class' relpages/reltuples columns seem pretty out of date for the toast table, this might be a variant of the problem reported here: http://archives.postgresql.org/pgsql-admin/2011-05/msg00101.php which was patched here: http://git.postgresql.org/gitweb/?p=postgresql.git&a=commitdiff&h=b503da135ab0bdd97ac3d3f720... although that patch hasn't actually made it into any shipping release yet :-( I'm not entirely convinced that you're seeing a related issue, because Florian was complaining of too many autovacuums not too few, but if you cross your eyes a bit and assume the symptom is "poor autovacuum scheduling" then maybe the same problem explains both. Another post-8.4.5 bug fix that could affect autovacuum's promptness is http://git.postgresql.org/gitweb/?p=postgresql.git&a=commitdiff&h=fab2af30d6bb4ca893e2e9bf96... > Whilst debugging, I found that there seems to be a large amount of the old 'PD_ALL_VISIBLE incorrectly set...' warnings emitted during the autovacuum run. If that were the issue, manual vacuums would be subject to it too. regards, tom lane ^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2011-08-09 15:03 UTC | newest] Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2011-08-03 14:23 PD_ALL_VISIBLE flag set - autovacuum ignoring dead tuples Tom Lanyon <tom+pgsql-admin@oneshoeco.com> 2011-08-09 15:03 ` Tom Lane <tgl@sss.pgh.pa.us>
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