Re: Performance

Bert --

You don't include some necessary details:

What version of postgres ? (8.x is noticably better at that OR / IN stuff I think, at least to some degree)

Please include some info about your setup -- what are the settings in the postgres config file (effective_cache_size, random_page_cost, work_mem [for postgres 8.x) or sort_mem in 7.x)

Perhaps some info about the server in question (OS, amount of RAM, # of disks and their setup)

Please also post the results of several EXPLAIN ANALYZE <sql here>; this will help people see what decisions the planner is making. Perhaps best to show one that is small, an intermdediate size and one that is painfully slow (the explain analyze has to run the actual query in question so I realize that this may be too slow, but some examples will help).

Greg Williamson
DBA
GlobeXplorer LLC

-----Original Message-----
From: pgsql-general-owner(at)postgresql(dot)org on behalf of Bert
Sent: Sat 4/22/2006 4:18 PM
To: pgsql-general(at)postgresql(dot)org
Cc:
Subject: [GENERAL] Performance

Hi List
I have maybe an easy question but i do not find an answer, i have this
SQL query:

SELECT geom,group,production_facs FROM south_america
WHERE municipio = ''
OR municipio = 'ACRE'
OR municipio = 'ADJUNTAS'
OR municipio = 'AGUADA'

The performance of this query is quite worse as longer it gets, its
possible that this query gets over 20 to 30 OR comparisons, but then
the performance is really worse, is it possible to speed it up?
Thanks
Clemens

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