From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
cc: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: allowing extensions to control planner behavior
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Comments: In-reply-to Robert Haas <robertmhaas@gmail.com>
	message dated "Tue, 27 Aug 2024 15:11:15 -0400"
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Date: Tue, 27 Aug 2024 16:15:35 -0400
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Robert Haas <robertmhaas@gmail.com> writes:
> I believe the minimum viable product here
> is probably something like:

> - control over scan methods
> - control over index selection
> - control over join methods
> - control over join order

Seems reasonable.  It might be possible to say that our answer
to "control over join order" is to provide a hook that can modify
the "joinlist" before it's passed to make_one_rel.  If you want
to force a particular join order you can rearrange that
list-of-lists-of-range-table-indexes to do so.  The thing this
would not give you is control over which rel is picked as outer
in any given join step.  Not sure how critical that bit is.

			regards, tom lane