Message-ID: <4436805A.1040507@archonet.com>
Date: Fri, 07 Apr 2006 16:08:10 +0100
From: Richard Huxton <dev@archonet.com>
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To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Brian Herlihy <btherl@yahoo.com.au>,
	pgsql-performance@postgresql.org
Subject: Spotting planner errors (was Re: Query planner is using wrong index.)
References: <20060407064108.49532.qmail@web52315.mail.yahoo.com>
	<11739.1144420493@sss.pgh.pa.us>
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Tom Lane wrote:
> Brian Herlihy <btherl@yahoo.com.au> writes:
>> Before I go, I have a question - From discussions on the Postgresql irc
>> channel, and from reading the TODO list on the website, I am under the
>> impression that there are no plans to allow optimizer hints, such as "use index
>> table_pkey".  Is this really true?
> 
> I personally don't think it's a good idea: the time spent in designing,
> implementing, and maintaining a usable hint system would be significant,
> and IMHO the effort is better spent on *fixing* the optimizer problems
> than working around them.

Tom - does the planner/executor know it's got row estimates wrong? That 
is, if I'm not running an EXPLAIN ANALYSE is there a point at which we 
could log "planner estimate for X out by factor of Y"?

-- 
   Richard Huxton
   Archonet Ltd