From: Robert Treat <xzilla@users.sourceforge.net>
To: pgsql-hackers@postgresql.org
Cc: Gregory Stark <stark@enterprisedb.com>
Cc: josh@agliodbs.com, "Jim C. Nasby" <jim@nasby.net>
Cc: pgsql-performance@postgresql.org
Subject: Re: [HACKERS] Hints proposal
Date: Tue, 17 Oct 2006 22:18:52 -0400
Message-ID: <200610172218.53194.xzilla@users.sourceforge.net> (raw)
In-Reply-To: <87odsg17uy.fsf@enterprisedb.com>
References: <20061012151439.GT28647@nasby.net>
<200610121358.22739.josh@agliodbs.com>
<87odsg17uy.fsf@enterprisedb.com>
On Friday 13 October 2006 12:46, Gregory Stark wrote:
> Josh Berkus <josh@agliodbs.com> writes:
> >> > I actually think the way to attack this issue is to discuss the kinds
> >> > of errors the planner makes, and what tweaks we could do to correct
> >> > them. Here's the ones I'm aware of:
> >> >
> >> > -- Incorrect selectivity of WHERE clause
> >> > -- Incorrect selectivity of JOIN
> >> > -- Wrong estimate of rows returned from SRF
> >> > -- Incorrect cost estimate for index use
> >> >
> >> > Can you think of any others?
>
> -- Incorrect estimate for result of DISTINCT or GROUP BY.
Yeah, that one is bad. I also ran into one the other day where the planner
did not seem to understand the distinctness of a columns values across table
partitions...
--
Robert Treat
Build A Brighter LAMP :: Linux Apache {middleware} PostgreSQL
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To: pgsql-performance@postgresql.org
Cc: xzilla@users.sourceforge.net, pgsql-hackers@postgresql.org, stark@enterprisedb.com, jim@nasby.net
Subject: Re: [HACKERS] Hints proposal
In-Reply-To: <200610172218.53194.xzilla@users.sourceforge.net>
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