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Message-ID: <4E04889B.2030806@optrak.com>
Date: Fri, 24 Jun 2011 13:52:43 +0100
From: Mark Thornton <mthornton@optrak.com>
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To: Harry Mantheakis <harry.mantheakis@riskcontrollimited.com>
CC: pgsql-performance@postgresql.org
Subject: Re: Long Running Update
References: <4E035649.20007@riskcontrollimited.com>
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On 23/06/11 16:05, Harry Mantheakis wrote:
> Hello
>
> I am attempting to run an update statement that copies two fields from 
> one table to another:
>
>
> UPDATE
>   table_A
> SET
> (
>   field_1
> , field_2
> ) = (
> table_B.field_1
> , table_B.field_2
> )
> FROM
> table_B
> WHERE
> table_B.id = table_A.id
> ;
>

I frequently get updates involving a FROM clause wrong --- the resulting 
table is correct but the running time is quadratic. You might want to 
try a series of smaller examples to see if your query displays this 
behaviour.

Mark Thornton