Re: How to force an Index ?

From: Bruno Wolff III <bruno(at)wolff(dot)to>
To: Rhaoni Chiu Pereira <rhaoni(at)sistemica(dot)info>
Cc: Lista PostgreSQL <pgsql-admin(at)postgresql(dot)org>
Subject: Re: How to force an Index ?
Date: 2003-08-26 19:45:58
Message-ID: 20030826194558.GA19181@wolff.to
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On Tue, Aug 26, 2003 at 16:11:56 -0300,
Rhaoni Chiu Pereira <rhaoni(at)sistemica(dot)info> wrote:
> Hi List,
>
> I'm looking for a way to force an Index to be used in a SQL query. In a
> Oracle SQL query it would be like:
>
> Select /*+ my_index*/ * from my_table where my_name="rhaoni";
>
> So it would use the index my_index to execute the query. How can I make this
> in a PostgreSQL SQL query.

There isn't a way to force specific indexes to be used. You can raise the
cost of sequential scans so that index scans will almost always be used
if they are possible. Use: set enable_seqscan = false;

In general it is best to use this only to find out why an index scan isn't
being used and then potentially change some cost functions so that the
proper plan is chosen.

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