From: Tom Lane <tgl@sss.pgh.pa.us>
To: Shawn <postgres@xmtservices.net>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: Slow Query
Date: Sat, 01 Sep 2007 14:09:54 -0400
Message-ID: <22800.1188670194@sss.pgh.pa.us> (raw)
In-Reply-To: <20070901102947.0c0a50a3@boffin.xmtservices.net>
References: <20070901102947.0c0a50a3@boffin.xmtservices.net>
Shawn <postgres@xmtservices.net> writes:
> update shawns_data set alias = null;
> Alias is a type varchar(8)
> The table has 26 fields per record and there are about 15,700
> records. The server hardware is a dual QUAD-CORE Intel 2 GHz XEON dell
> 2950 server with 4 drive SAS RAID-5 array, and 16G of RAM. The OS is
> Slackware 11 with some updatews and Postgres v8.2.4 built from source.
> Even after VACUUM this simple line takes 35 sec to complete.
Seems like a lot. Table bloat maybe (what does VACUUM VERBOSE say about
this table)? An unreasonably large number of indexes to update?
Foreign key checks? (Though unless you have FKs pointing at alias,
I'd think 8.2 would avoid needing to make any FK checks.)
Could we see EXPLAIN ANALYZE output for this operation? (If you don't
really want to zap the column right now, wrap the EXPLAIN in
BEGIN/ROLLBACK.)
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, postgres@xmtservices.net
Subject: Re: Slow Query
In-Reply-To: <22800.1188670194@sss.pgh.pa.us>
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