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Re: Delete query takes exorbitant amount of time

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com>,Karim A Nassar <Karim(dot)Nassar(at)NAU(dot)EDU>,Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>,pgsql-performance(at)postgresql(dot)org
Subject: Re: Delete query takes exorbitant amount of time
Date: 2005-03-29 15:31:50
Message-ID: 22527.1112110310@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> If action is NO ACTION or RESTRICT then 
> 	we need to SELECT at most 1 row that matches the criteria
> 	which means we can use LIMIT 1

> If action is CASCADE, SET NULL, SET DEFAULT then
> 	we need to UPDATE or DELETE all rows that match the criteria
> 	which means we musnt use LIMIT and need to use FOR UPDATE

Huh?  UPDATE/DELETE don't use FOR UPDATE.  I think you have failed
to break down the cases sufficiently.  In particular it matters which
side of the RI constraint you are working from ...

			regards, tom lane

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