Re: pg_clog questions

"Benjamin Krajmalnik" <kraj(at)illumen(dot)com> writes:
>>> While checking our server, I noticed quite a few files in the pg_clog
>>> directory.
>>> Is there a maintenance task which can be run to purge the files which
>>> are no longer needed?

>> VACUUM. If they're not disappearing, you aren't running an adequate
>> vacuum regime --- missing out some databases, perhaps?

> I have autovacuum turned on with the default settings.

Hm. I believe that autovac only does database-wide vacuums when it
thinks they're necessary to prevent transaction wraparound failures.
Which would mean that it'd let pg_clog grow to something on the order
of half a gig before any truncation would happen. That's probably
insufficiently aggressive :-(

Alvaro, Matthew, any thoughts about improving that? It strikes me that
Alvaro's work-in-progress on maintaining per-table xmin info would allow
truncation of clog without actually insisting on a database-wide VACUUM,
but that's not going to be any help for existing releases.

regards, tom lane