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Re: Slow update

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Hilary Forbes <hforbes(at)dmr(dot)co(dot)uk>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Slow update
Date: 2005-09-12 14:07:26
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Hilary Forbes <hforbes(at)dmr(dot)co(dot)uk> writes:
> I need to set the value of a field in table A to a value in table B depending on the existence of the record in table B.  So what I have done is

> UPDATE tableA set a.val1=b.somefield FROM tableA a, tableB b WHERE a.key1=b.key1;

You've written an unconstrained join to a second copy of tableA.

			regards, tom lane

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  • Slow update at 2005-09-12 09:14:25 from Hilary Forbes

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