From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alex Deucher <alexdeucher@gmail.com>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: postgres 7.4 vs 8.x redux: query plans
Date: Tue, 03 Apr 2007 01:28:03 -0400
Message-ID: <17931.1175578083@sss.pgh.pa.us> (raw)
In-Reply-To: <a728f9f90704022209x1cd688f6pa9c8c2584376897e@mail.gmail.com>
References: <a728f9f90704022209x1cd688f6pa9c8c2584376897e@mail.gmail.com>
"Alex Deucher" <alexdeucher@gmail.com> writes:
> and here are the query plans referenced in my last email (apologies if
> you get these twice, they didn't seem to go through the first time,
> perhaps due to size?). I cut out the longer ones.
The first case looks a whole lot like 8.2 does not think it can use an
index for LIKE, which suggests strongly that you've used the wrong
locale in the 8.2 installation (ie, not C).
The second pair of plans may look a lot different but in principle they
ought to perform pretty similarly. I think the performance differential
may at root be that string comparison is way more expensive in the 8.2
installation, which again is possible if you went from C locale to some
other locale.
In short: check out "show lc_collate" in both installations.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, alexdeucher@gmail.com
Subject: Re: postgres 7.4 vs 8.x redux: query plans
In-Reply-To: <17931.1175578083@sss.pgh.pa.us>
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