Re: *_collapse_limit, geqo_threshold

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
Cc: "Robert Haas" <robertmhaas(at)gmail(dot)com>, "Dimitri Fontaine" <dim(at)hi-media(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: *_collapse_limit, geqo_threshold
Date: 2009-07-08 21:46:02
Message-ID: 10841.1247089562@sss.pgh.pa.us
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"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> writes:
> For a moment it seemed logical to suggest a session GUC for the seed,
> so if you got a bad plan you could keep rolling the dice until you got
> one you liked; but my right-brain kept sending shivers down my spine
> to suggest just how uncomfortable it was with that idea....

If memory serves, we actually had exactly that at some point. But I
think the reason it got taken out was that it interfered with the
behavior of the random() function for everything else. We'd have to
give GEQO its own private random number generator.

regards, tom lane

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