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Re: Optimizing a request

From: Jean-Max Reymond <jmreymond(at)gmail(dot)com>
To: Gary Doades <gpd(at)gpdnet(dot)co(dot)uk>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Optimizing a request
Date: 2004-08-31 19:42:56
Message-ID: (view raw or whole thread)
Lists: pgsql-performance
----- Original Message -----
From: Gary Doades <gpd(at)gpdnet(dot)co(dot)uk>
Date: Tue, 31 Aug 2004 20:21:49 +0100
Subject: Re: [PERFORM] Optimizing a request
To: pgsql-performance(at)postgresql(dot)org


> Have you run ANALYZE on this database after creating the indexes or loading the data? 
the indexes are created and the data loaded and then, I run vacuum analyze.

>What percentage of rows in the "article" table are likely to match
the keys selected from  the "rubrique" table?
only 1 record.

If it is likely to fetch a high proportion of the rows from article
then it may be best that a seq scan is performed.
What are your non-default postgresql.conf settings? It may be better
to increase the default_statistics_target (to say 100 to 200) before
running ANALYZE and then re-run the query.
yes,  default_statistics_target is set to the default_value.
I have just increased  shared_buffers and effective_cache_size to give
advantage of 1 Mb RAM

Jean-Max Reymond
CKR Solutions

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