Re: specific query (not all) on Pg8 MUCH slower than Pg7

From: "Alexander Staubo" <alex(at)purefiction(dot)net>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Susan Russo" <russo(at)morgan(dot)harvard(dot)edu>, pgsql-performance(at)postgresql(dot)org, harvsys(at)morgan(dot)harvard(dot)edu
Subject: Re: specific query (not all) on Pg8 MUCH slower than Pg7
Date: 2007-05-08 14:59:30
Message-ID: 88daf38c0705080759o2e5771c3qdf1b34baa581fc53@mail.gmail.com
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On 5/8/07, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> You're not getting the indexscan optimization of the LIKE clause, which
> is most likely due to having initdb'd the 8.1 installation in something
> other than C locale. You can either redo the initdb in C locale (which
> might be a good move to fix other inconsistencies from the 7.3 behavior
> you're used to) or create a varchar_pattern_ops index on the column(s)
> you're using LIKE with.

Given the performance implications of setting the wrong locale, and
the high probability of accidentally doing this (I run my shells with
LANG=en_US.UTF-8, so all my databases have inherited this locale), why
is there no support for changing the database locale after the fact?

# alter database test set lc_collate = 'C';
ERROR: parameter "lc_collate" cannot be changed

Alexander.

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