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Re: WIP: cross column correlation ...

From: PostgreSQL - Hans-Jürgen Schönig <postgres(at)cybertec(dot)at>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers Hackers <pgsql-hackers(at)postgresql(dot)org>, Boszormenyi Zoltan <zb(at)cybertec(dot)at>
Subject: Re: WIP: cross column correlation ...
Date: 2011-02-23 14:54:11
Message-ID: 1CFB88AD-B7E4-4CED-A048-2292E5888B05@cybertec.at (view raw or flat)
Thread:
Lists: pgsql-hackers
>>> 
>> 
>> cheapest and easiest solution if you run into this: add "fake" functions which the planner cannot estimate properly.
>> use OR to artificially prop up estimates or use AND to artificially lower them. there is actually no need to redesign the schema to get around it but it is such an ugly solution that it does not even deserve to be called "ugly" ...
>> however, fast and reliable way to get around it.
> 
> We couldn't possibly design a hint mechanism that would be uglier or
> less future-proof than this workaround (which, by the way, I'll keep
> in mind for the next time I get bitten by this).
> 
> -- 
> Robert Haas
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
> 


i think the main issue is: what we do is ugly because of despair and a lack of alternative ... what you proposed is ugly by design ;).
overall: the workaround will win the ugliness contest, however ;).

	many thanks,

		hans

--
Cybertec Schönig & Schönig GmbH
Gröhrmühlgasse 26
A-2700 Wiener Neustadt, Austria
Web: http://www.postgresql-support.de


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