Re: Unexplained Major Vacuum Archive Activity During Vacuum

On 11/01/2012 09:18 AM, Kevin Grittner wrote:

> Did you bulk load this data (possibly through restoring pg_dump
> output)? If so, and you have not explicitly run VACUUM FREEZE
> afterward, the vacuum noticed that it was time to freeze all of these
> tuples.

Ok, that might explain it, then. We did in fact just upgrade from 8.2 to
9.1 about 2 weeks ago. And no, I didn't do a VACUUM FREEZE, just a
VACUUM ANALYZE to make sure stats were ready. I'm still a little
uncertain what the tangible difference is between a FREEZE and a regular
VACUUM. I get that it sets freeze_min_age to 0, but why does that even
matter? Is 50M out of 2B not good enough? Every VACUUM knocks the
counter back to the minimum, so I guess I don't get the justification
for magically forcing the minimum to be lower.

Of course, all that page marking would definitely produce a butt-ton of
transaction logs. So at least that makes sense. :)

Thanks, Keven!

> You haven't mentioned anything that should be taken as evidence of
> corruption or any unusual behavior on the part of PostgreSQL.

No, but I was a little freaked out by the unexplained activity.

--
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604
312-444-8534
sthomas(at)optionshouse(dot)com

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