It appears to me that in my 8.4.0 system, autovacuum is running to prevent
wraparound contrary to the documentation. I have it set to a tables'
relfrozenxid has to get to 1.5 billion before that kicks in:
> show autovacuum_freeze_max_age;
1500000000
> show vacuum_freeze_table_age;
1300000000
> show vacuum_freeze_min_age;
1000000000
Table foo has an age just over 1 billion, still well under the
freeze_table_age:
> select age(relfrozenxid) from pg_class where relname='foo';
age
------------
1055823634
yet, I see this in pg_stat_activity:
autovacuum: VACUUM public.foo (to prevent wraparound)
One possibly interesting thing is that this seems to have started just after
I set foo's autovacuum_analyze_scale_factor to 0.01, since I wanted more
frequent analyze runs. I wonder if that could be related.
Any ideas? These wraparound autovacuums are taking up my vacuum workers so
no analyze workers can run.
Thanks!
Gordon
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