Re: enable_joinremoval

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> wrote:
>>> 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.  That always seems what I want to look at for answering 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.  You 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