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Message-ID: <20060510162143.96628.qmail@web50306.mail.yahoo.com>
Date: Wed, 10 May 2006 09:21:43 -0700 (PDT)
From: <ogjunk-pgjedan@yahoo.com>
Subject: Multi-column index not used, new flipped column index is
To: pgsql-sql@postgresql.org
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii

Hi,

I'm using PG 8.0.3 and recently spotted a query that was not using a multi-column index I had created.
The index looks like:

  CREATE INDEX ..... ON FooTable(fkColumnOne, fkColumnTwo);

The query that was not using the index was using:

  SELECT .... a bunch of columns and joins .... WHERE FooTable.fkColumnTwo=1000;

So I added another index where the indexed columns are flipped:

  CREATE INDEX ..... ON FooTable(fkColumnTwo, fkColumnOne);
 
Now the query started to use that index -- gooooood!
But now I have 2 indices that are nearly the same, and that means overhead during INSERTs/DELETEs. :(

Is there a way to get this to use that first index, so I don't have to have this additional index?
If I had PG 8.1.3, would PG know how to use that first index?  I seem to recall something about this somewhere... but I don't see it at http://www.postgresql.org/docs/whatsnew .

Thanks,
Otis