From: | Dr NoName <spamacct11(at)yahoo(dot)com> |
---|---|
To: | Ragnar "Hafsta" <gnari(at)simnet(dot)is> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: indexes are fucked |
Date: | 2005-08-02 18:24:25 |
Message-ID: | 20050802182425.50458.qmail@web31501.mail.mud.yahoo.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-general |
> the seqscan is cheaper when a large enough
> proportion
> (maybe 5%) of rows are retrieved, and indeed the
> cost
> is estimated at 39014
very good explanation. thank you.
> try to increase statistics for this column:
>
> ALTER TABLE render ALTER COLUMN person_id
> SET STATISTICS 1000;
> ANALYZE render;
>
> 1000 is the maximum value, and probably overkill,
> but you might start with that. If this helps, you
> can
> try to lower values until you find the lowest one
> that still suits your data. Usually, 200 is enough.
ok, we're getting into voodoo territory. What is this
"statistics"? How can I see what the current value is?
How can I estimate what's a "good" value? Where can I
find more information about this?
thanks,
Eugene
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