From: | Doug McNaught <doug(at)wireboard(dot)com> |
---|---|
To: | "Thomas T(dot) Thai" <tom(at)minnesota(dot)com> |
Cc: | PostgreSQL General <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: help with getting index scan |
Date: | 2002-02-25 15:38:13 |
Message-ID: | m3pu2tzi56.fsf@varsoon.denali.to |
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Lists: | pgsql-general |
"Thomas T. Thai" <tom(at)minnesota(dot)com> writes:
> > > i can't seem to get index scan to work on table phone_cat_address. here
> > > are my schemas:
> >
> > Standard question: have you run VACUUM ANALYZE?
>
> yes :) before each test.
Excellent. ;)
>
> > Also, the estimate of rows returned from the phone_cat_address scan is
> > pretty large--how large is the table itself? Sequential scan is
> > actually faster if you're going to end up returning most of the rows
> > in the table...
>
> yellowpages=# select count(*) from phone_cat_address;
> count
> --------
> 336702
> (1 row)
>
> type typical results should be a tiny fraction of that number.
Well, EXPLAIN is indicating (unless I misread it) that the estimate of
rows returned is 336702, so it's not surprising that it opts for a
sequential scan. Is this under 7.1 or 7.2? The latter keeps much
better statistics about table populations...
-Doug
--
Let us cross over the river, and rest under the shade of the trees.
--T. J. Jackson, 1863
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