From: | Matteo Beccati <php(at)beccati(dot)com> |
---|---|
To: | Jaime Casanova <jcasanov(at)systemguards(dot)com(dot)ec> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: regression in analyze |
Date: | 2008-11-07 08:21:03 |
Message-ID: | 4913FA6F.8010608@beccati.com |
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Thread: | |
Lists: | pgsql-hackers |
Hi,
> * We approximate "never vacuumed" by "has relpages = 0", which
> * means this will also fire on genuinely empty relations. Not
> * great, but fortunately that's a seldom-seen case in the real
> * world, and it shouldn't degrade the quality of the plan too
> * much anyway to err in this direction.
> */
> if (curpages < 10 && rel->rd_rel->relpages == 0)
> curpages = 10;
>
>
> commenting that two lines make the estimates correct. now that we have
> plan invalidation that hack is still needed?
> i know that as the comment suggest this has no serious impact but
> certainly this is user visible.
I guess the reason is that a 0 estimate for a non empty table which was
analyzed before the data was inserted and not yet analyzed again could
cause much more troubles... anyway, I was just curious to get an
"official" anwser ;)
Cheers
--
Matteo Beccati
OpenX - http://www.openx.org
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