Horton

Re: optimizing Postgres queries

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Teran <david.teran@cluster9.com>
Cc: Shridhar Daithankar <shridhar_daithankar@myrealbox.com>, pgsql-performance@postgresql.org
Date: 2004-01-05T18:52:40Z
Lists: pgsql-performance 
David Teran <david.teran@cluster9.com> writes:
> What we found out now is that a query with a single 'where' works fine, 
> the query planer uses the index but when we have 'two' where clauses it 
> does not use the index anymore:

> EXPLAIN ANALYZE SELECT columns...  FROM "KEY_VALUE_META_DATA" t0 WHERE 
> (t0."ID_VALUE" = 14542); performs fine, less than one millisecond.

> EXPLAIN ANALYZE SELECT columns...  FROM "KEY_VALUE_META_DATA" t0 WHERE 
> (t0."ID_VALUE" = 14542 OR t0."ID_VALUE" = 14550); performs bad: about 
> 235 milliseconds.

Please, when you ask this sort of question, show the EXPLAIN ANALYZE
output.  It is not a virtue to provide minimal information and see if
anyone can guess what's happening.

			regards, tom lane