Re: Optimizer hook

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Julius Stroffek <Julius(dot)Stroffek(at)Sun(dot)COM>
Cc: pgsql-patches(at)postgresql(dot)org
Subject: Re: Optimizer hook
Date: 2007-09-26 00:47:54
Message-ID: 9710.1190767674@sss.pgh.pa.us
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Julius Stroffek <Julius(dot)Stroffek(at)Sun(dot)COM> writes:
>> Why would you care? Seems like forcing that to not happen is actively
>> making it stupider.
>>
> To better compare the algorithms and possibly not for final solution at
> the beginning. If we would implement 10 algorithms and want to pickup
> just 3 best ones to be used and throw 7 away.

Well, you could in any case force the same decision to be made in every
invocation, for example by driving it off a GUC variable. The idea you
have here seems to be "it'll be the same choice in every sub-problem,
only we won't know which one afterwards", which doesn't seem at all
helpful for planner testing purposes.

> Yes, the example in dummy.c is really stupider, but it could be done
> in more clever way.

I think dummy.c kinda proves my point: more than half the code is
accomplishing nothing except to duplicate the behavior of
make_rel_from_joinlist.

regards, tom lane

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