Re: [HACKERS] bushy plans

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От Bruce Momjian
Тема Re: [HACKERS] bushy plans
Дата
Msg-id 199902150531.AAA29547@candle.pha.pa.us
обсуждение исходный текст
Ответ на Re: [HACKERS] bushy plans  (Vadim Mikheev <vadim@krs.ru>)
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> > Please tell me what they are supposed to do.  I can get it working, I
> > think.  I will not remove it.  I have ifdef'ed it, though.  If you tell
> > me what it is, I will check it to see if it works.
> 
> It doesn't work (failed assertion).
> 
> Well, currently both geqo and old optimizer produces
> left-sided plans: inner relation of an join is always
> _base_ relation (not join relation). In bushy plans
> both outer and inner relations may be join ones.
> ~1.5 - 2 years ago I added right-sided plans:
> outer relation is base, inner relation may be join.
> Sometimes right-sided plans are 30% faster than left-sided.
> Bushy plans could be more faster...
> BTW, I broke execution of right-sided plans ~ 1 year ago
> while implementing subqueries (near materialization node)
> and still have no time to fix it (seems no one except me
> used them so I didn't worry about this -:)).

This explaination helps greatly.  This clears up what is happening in
the code.  I will keep the bushy stuff, and see if I can get it working,
though if the problem is outside of the optimizer, I will have trouble.

--  Bruce Momjian                        |  http://www.op.net/~candle maillist@candle.pha.pa.us            |  (610)
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