Re: Estimation problem with a LIKE clause containing a /

From: "Guillaume Smet" <guillaume(dot)smet(at)gmail(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Estimation problem with a LIKE clause containing a /
Date: 2007-11-08 10:08:33
Message-ID: 1d4e0c10711080208n6c9875b4tf5882da3ced18532@mail.gmail.com
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Tom,

On Nov 8, 2007 12:14 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I've applied a patch that might help you:
> http://archives.postgresql.org/pgsql-committers/2007-11/msg00104.php

AFAICS, it doesn't seem to fix the problem. I just compiled
REL8_1_STABLE branch and I still has the following behaviour:
lbo=# ANALYZE cms_items;
ANALYZE
lbo=# explain analyze select * from cms_items where ancestors LIKE '1062/%';
QUERY PLAN
------------------------------------------------------------------------------------------------------------
Seq Scan on cms_items (cost=0.00..688.26 rows=1 width=103) (actual
time=0.009..22.258 rows=11326 loops=1)
Filter: ((ancestors)::text ~~ '1062/%'::text)
Total runtime: 29.835 ms
(3 rows)

lbo=# show lc_collate;
lc_collate
-------------
fr_FR.UTF-8
(1 row)

Do you see any reason why your patch doesn't change anything in this case?

Thanks.

--
Guillaume

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