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Re: Hashjoin startup strategy (was Re: Getting different number of results when using hashjoin on/off)

From: Greg Stark <gsstark(at)mit(dot)edu>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Mario Weilguni" <mario(dot)weilguni(at)icomedias(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Hashjoin startup strategy (was Re: Getting different number of results when using hashjoin on/off)
Date: 2005-11-29 00:25:58
Message-ID: 87r790i9k9.fsf@stark.xeocode.com (view raw or flat)
Thread:
Lists: pgsql-hackers
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> In particular, the executor knows that the outer subplan is parameterless
> and therefore should deliver the same results each time (modulo volatile
> functions of course), so after the first cycle it could know that there's no
> point in trying the early fetch on that side.

> Anyone have any other ideas?

I suspect this is obvious but since you asked, there isn't any way to keep
around the hash table and just reuse it repeatedly instead of having to rescan
the data over and over is there?

-- 
greg


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