Re: *_collapse_limit, geqo_threshold

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, 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: 2009-07-10 15:22:43
Message-ID: 603c8f070907100822n4e723d9dnbbf6bbf6a573fda1@mail.gmail.com
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On Wed, Jul 8, 2009 at 4:57 PM, Tom Lane<tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Well, the reason I'm not voting for #3 is that it looks like a lot of
> work to implement something that would basically be a planner hint,
> which I'm generally against; furthermore, it's a hint that there's been
> no demand for.  (We're not even certain that anyone is using the ability
> to *fully* specify the join order, much less wanting some undetermined
> compromise between manual and automatic control.)  And anyway I didn't
> hear anyone volunteering to do it.  So the realistic alternatives are
> #1, #2, or "do nothing"; and out of those I like #2.

I took a look at this and it seems that #3 can be implemented with
essentially no additional code (the handful of lines I added where
more than balanced out by some simplifications in ruleutils.c). Of
course you still don't have to like it. :-)

Patch attached.

...Robert

Attachment Content-Type Size
collapse_limit.patch text/x-diff 29.9 KB

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