| From: | "A(dot) Kretschmer" <andreas(dot)kretschmer(at)schollglas(dot)com> |
|---|---|
| To: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: slow result |
| Date: | 2007-01-23 10:53:35 |
| Message-ID: | 20070123105335.GD24927@a-kretschmer.de |
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| Lists: | pgsql-performance |
am Tue, dem 23.01.2007, um 11:34:52 +0100 mailte Laurent Manchon folgendes:
> Hi,
>
> I have a slow response of my PostgreSQL database 7.4 using this query below
> on a table with 800000 rows:
>
> select count(*)from tbl;
If i remember correctly, i saw this question yesterday on an other
list...
Answer:
Because PG force a sequencial scan. You can read a lot about this in the
archives. Here some links to explanations:
http://www.pervasive-postgres.com/instantkb13/article.aspx?id=10117&cNode=0T1L6L
http://sql-info.de/postgresql/postgres-gotchas.html#1_7
http://www.varlena.com/GeneralBits/49.php
Hope that helps, Andreas
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Andreas Kretschmer
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