Re: Why is vacuum_freeze_min_age 100m?

Robert,

> Ah.  Yeah, I agree with Tom: how would it help to make this smaller?
> It seems like that could possibly increase I/O, if the old data is
> changing at all, but even if it doesn't it I don't see that it saves
> you anything to freeze it sooner.

Before 8.4, it actually does on tables which are purely cumulative
(WORM).  Within a short time, say, 10,000 transactions, the rows to be
frozen are still in the cache.  By 100m transactions, they are in an
archive partition which will need to be dragged from disk.  So if I know
they won't be altered, then freezing them sooner would be better.

However, I can easily manage this through the autovacuum settings.  I
just wanted confirmation of what I was thinking.

--
Josh Berkus
PostgreSQL Experts Inc.
www.pgexperts.com