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Date: Mon, 29 Mar 2010 12:29:11 -0400
Message-ID: <603c8f071003290929x3d36be21t848d2f7244c0cf5b@mail.gmail.com>
Subject: Re: enable_joinremoval
From: Robert Haas <robertmhaas@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Greg Smith <greg@2ndquadrant.com>, Simon Riggs <simon@2ndquadrant.com>,
	pgsql-hackers@postgresql.org
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On Mon, Mar 29, 2010 at 12:17 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> On Mon, Mar 29, 2010 at 12:03 PM, Greg Smith <greg@2ndquadrant.com> wrot=
e:
>>> at the top of my list in this area for 9.1 is to track down the rumored
>>> patch that exports information about the rejected plans considered and =
get
>>> that comitted. =A0That always seems what I want to look at for answerin=
g the
>>> question "why this plan instead of what I was expecting?"
>
>> Having looked at that patch, I am skeptical of it, but we can
>> certainly take a fresh look.
>
> The problem with this line of thought is that it imagines you can look
> at worked-out alternative plans. =A0You can't, because the planner doesn'=
t
> pursue rejected alternatives that far (and you'd not want to wait long
> enough for it to do so...)

Right.  And that's not what the patch did.  But a detailed discussion
of this topic should be (a) conducted on a separate thread and (b)
occur after we've all refamiliarized ourselves with it.

...Robert