Message-ID: <43792523.5090003@noao.edu>
Date: Mon, 14 Nov 2005 17:00:35 -0700
From: Steve Wampler <swampler@noao.edu>
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To: Tom Lane <tgl@sss.pgh.pa.us>
CC: Postgres-performance <pgsql-performance@postgresql.org>
Subject: Re: Help speeding up delete
References: <43790A99.9050603@noao.edu> <4162.1132011763@sss.pgh.pa.us>
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Tom Lane wrote:
> Steve Wampler <swampler@noao.edu> writes:
> 
>>We've got an older system in production (PG 7.2.4).  Recently
>>one of the users has wanted to implement a selective delete,
>>but is finding that the time it appears to take exceeds her
>>patience factor by several orders of magnitude.  Here's
>>a synopsis of her report.  It appears that the "WHERE
>>id IN ..." is resulting in a seq scan that is causing
>>the problem, but we're not SQL expert enough to know
>>what to do about it.
> 
> 
>>Can someone point out what we're doing wrong, or how we
>>could get a (much) faster delete?  Thanks!
> 
> 
> Update to 7.4 or later ;-)

I was afraid you'd say that :-)  I'm not officially involved in
this project anymore and was hoping for a fix that wouldn't drag
me back in.  The security issues aren't a concern because this
DB is *well* hidden from the outside world (it's part of a telescope
control system behind several firewalls with no outside access).
However, the data-loss-grade bugs issue *is* important.  We'll
try to do the upgrade as soon as we get some cloudy days to
actually do it!

Is the performance behavior that we're experiencing a known
problem with 7.2 that has been addressed in 7.4?  Or will the
upgrade fix other problems while leaving this one?

> Quite seriously, if you're still using 7.2.4 for production purposes
> you could justifiably be accused of negligence.  There are three or four
> data-loss-grade bugs fixed in the later 7.2.x releases, not to mention
> security holes; and that was before we abandoned support for 7.2.
> You *really* need to be thinking about an update.

Thanks!
Steve
-- 
Steve Wampler -- swampler@noao.edu
The gods that smiled on your birth are now laughing out loud.