From: Andrew Sullivan <ajs@crankycanuck.ca>
To: pgsql-sql@postgresql.org
Subject: Re: Sequence vs. Index Scan
Date: Mon, 7 May 2007 06:58:29 -0400
Message-ID: <20070507105829.GB30076@phlogiston.dyndns.org> (raw)
In-Reply-To: <bf05e51c0705061145s43815026q49394acba8407c1f@mail.gmail.com>
References: <bf05e51c0705051405p29ee139fn30c9979f3772a1d4@mail.gmail.com>
<29507.1178410970@sss.pgh.pa.us>
<bf05e51c0705052125h33c1579ch652c978647d530d9@mail.gmail.com>
<c2d9e70e0705052137i44d56415ud7ec0a8fa9250e23@mail.gmail.com>
<bf05e51c0705061145s43815026q49394acba8407c1f@mail.gmail.com>
On Sun, May 06, 2007 at 01:45:54PM -0500, Aaron Bono wrote:
> Then I inserted 150 more records in the slow schema and pow - it started
> working like the fast schema.
>
> So my conclusion is that the function is being treated as volatile even
> though it is stable because the number of records is small.
I don't think that's the issue. If this is dependent on the
number of records, then for some reason the way the data is
structured means that the planner thinks a seqscan's a better bet.
This is probably due to distribution of the values. You could try
increasing the stats sample, and see if that helps.
A
--
Andrew Sullivan | ajs@crankycanuck.ca
This work was visionary and imaginative, and goes to show that visionary
and imaginative work need not end up well.
--Dennis Ritchie
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To: pgsql-sql@postgresql.org
Cc: ajs@crankycanuck.ca
Subject: Re: Sequence vs. Index Scan
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