Re: v7.2.3 versus v7.3 -> huge performance penalty for JOIN with UNION

From: Frank van Vugt <ftm(dot)van(dot)vugt(at)foxi(dot)nl>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Postgresql performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: v7.2.3 versus v7.3 -> huge performance penalty for JOIN with UNION
Date: 2002-12-03 15:23:51
Message-ID: 200212031623.51513.ftm.van.vugt@foxi.nl
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> Probably not, since the first thing it does is to flatten the
> sub-select, leaving it with a concatenation expression in the
> WHERE-clause.

Ah, I see.

So, I'll just split this thingy into two seperate queries, starting with
creating a temp table containing the straight subselect results.

> We really need to fix the planner to be able to do merge/hash on
> "arbitrary expression = arbitrary expression", not only "Var = Var".

I can get around it, so I'm not complaining ;-)

Tom, thanks a *lot* for the prompt responses !!

Best,

Frank.

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