From: Gregory Stark <stark@enterprisedb.com>
To: Craig Ringer <craig@postnewspapers.com.au>
Cc: Decibel! <decibel@decibel.org>
Cc: Chris Kratz <chris.kratz@vistashare.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Incorrect estimates on correlated filters
Date: Thu, 14 Aug 2008 11:12:00 +0100
Message-ID: <878wuzvrbj.fsf@oxford.xeocode.com> (raw)
In-Reply-To: <48A38ED3.8080500@postnewspapers.com.au>
References: <3642025c0808121459x75c8d9baq66194b87f5053ea3@mail.gmail.com>
<12707C41-48C3-4072-A152-46FAB1FEE1E2@decibel.org>
<48A38ED3.8080500@postnewspapers.com.au>
"Craig Ringer" <craig@postnewspapers.com.au> writes:
> It strikes me that there are really two types of query hint possible here.
>
> One tells the planner (eg) "prefer a merge join here".
>
> The other gives the planner more information that it might not otherwise
> have to work with, so it can improve its decisions. "The values used in
> this join condition are highly correlated".
This sounds familiar:
http://article.gmane.org/gmane.comp.db.postgresql.devel.general/55730/match=hints
Plus ça change...
--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's On-Demand Production Tuning
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To: pgsql-performance@postgresql.org
Cc: stark@enterprisedb.com, craig@postnewspapers.com.au, decibel@decibel.org, chris.kratz@vistashare.com
Subject: Re: Incorrect estimates on correlated filters
In-Reply-To: <878wuzvrbj.fsf@oxford.xeocode.com>
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