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Re: WIP: cross column correlation ...

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: PostgreSQL - Hans-Jürgen Schönig <postgres(at)cybertec(dot)at>, pgsql-hackers Hackers <pgsql-hackers(at)postgresql(dot)org>, Boszormenyi Zoltan <zb(at)cybertec(dot)at>
Subject: Re: WIP: cross column correlation ...
Date: 2011-02-24 01:09:10
Message-ID: 4D65AFB6.1000203@agliodbs.com (view raw or flat)
Thread:
Lists: pgsql-hackers
> Personally, I think the first thing we ought to do is add a real, bona
> fide planner hint to override the selectivity calculation manually,
> maybe something like this:
> 
> WHERE (x < 5 AND y = 1) SELECTIVITY (0.1);
> 
> Then, having provided a method for the DBA to extinguish the raging
> flames of searing agony which are consuming them while a crocodile
> chews off their leg and their boss asks them why they didn't use
> Oracle, we can continue bikeshedding about the best way of fixing this
> problem in a more user-transparent fashion.

Is there some way we can do that without adding the selectivity hint to
the query itself?  That's the biggest issue with hints.

-- 
                                  -- Josh Berkus
                                     PostgreSQL Experts Inc.
                                     http://www.pgexperts.com

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