From: | Zlatko Calusic <zlatko(at)iskon(dot)hr> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: Indexes not working (bug in 7.0.2?) |
Date: | 2000-09-04 21:02:49 |
Message-ID: | 87snrfx43q.fsf@atlas.iskon.hr |
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Lists: | pgsql-general |
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
> Zlatko Calusic <zlatko(at)iskon(dot)hr> writes:
> > It is now NOT using the index, and I don't understand why? Queries are
> > practically the same, tables are practically the same, why is postgres
> > using indexes in the first case and not in the second?
>
> Because it has substantially different ideas about the sizes of the
> two tables --- notice the different estimated row counts. If you
> haven't "vacuum analyzed" these tables recently, do so to bring the
> planner's statistics up-to-date, and then see what you get. You may
> also care to read the user's manual chapter about EXPLAIN,
> http://www.postgresql.org/users-lounge/docs/7.0/postgres/c4888.htm
>
Yes, thanks to all who helped. 'vacuum analyze' was the magical
incantation that helped.
I still have one uncertainty. Is it possible that after some time
postgres once again decides not to use indices (assuming I haven't run
'vacuum analyze' again)?
--
Zlatko
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