| 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 |
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| 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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