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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andrew Gierth <andrew@tao11.riddles.org.uk>
Cc: Andreas Karlsson <andreas@proxel.se>
Cc: David Fetter <david@fetter.org>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Early WIP/PoC for inlining CTEs
Date: Sun, 27 Jan 2019 10:21:55 -0500
Message-ID: <744.1548602515@sss.pgh.pa.us> (raw)
In-Reply-To: <87fttejl62.fsf@news-spur.riddles.org.uk>
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	<87fttejl62.fsf@news-spur.riddles.org.uk>

Andrew Gierth <andrew@tao11.riddles.org.uk> writes:
> I'm not sure we should nail down the rule that the absence of NOT
> MATERIALIZED will mean a multiply-referenced CTE is evaluated once. One
> would hope that in the future the planner might be taught to inline or
> not in that case depending on cost. I think it makes more sense to say
> that we never inline if MATERIALIZED is specified, that we always inline
> if NOT MATERIALIZED is specified, and that if neither is specified the
> planner will choose (but perhaps note that currently it always chooses
> only based on refcount).

I have no objection to documenting it like that; I just don't want us
to go off into the weeds trying to actually implement something smarter
for v12.

			regards, tom lane




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