| From: | Gregory Stark <stark(at)enterprisedb(dot)com> |
|---|---|
| To: | "Craig Ringer" <craig(at)postnewspapers(dot)com(dot)au> |
| Cc: | "Decibel!" <decibel(at)decibel(dot)org>, "Chris Kratz" <chris(dot)kratz(at)vistashare(dot)com>, <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Incorrect estimates on correlated filters |
| Date: | 2008-08-14 10:12:00 |
| Message-ID: | 878wuzvrbj.fsf@oxford.xeocode.com |
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| Lists: | pgsql-performance |
"Craig Ringer" <craig(at)postnewspapers(dot)com(dot)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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