From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andrew Gierth <andrew@tao11.riddles.org.uk>
cc: Andreas Karlsson <andreas@proxel.se>,
        Tomas Vondra <tomas.vondra@2ndquadrant.com>,
        Merlin Moncure <mmoncure@gmail.com>,
        Alvaro Herrera <alvherre@2ndquadrant.com>,
        Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
        Michael Paquier <michael@paquier.xyz>,
        Robert Haas <robertmhaas@gmail.com>,
        Andres Freund <andres@anarazel.de>,
        Thomas Munro <thomas.munro@enterprisedb.com>,
        David Fetter <david@fetter.org>,
        Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Early WIP/PoC for inlining CTEs
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Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Tue, 26 Feb 2019 09:51:38 -0500"
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Date: Tue, 09 Apr 2019 15:50:49 -0400
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I wrote:
> Andrew Gierth <andrew@tao11.riddles.org.uk> writes:
>> So what I think we need to do here is to forbid inlining if (a) the
>> refcount is greater than 1 and (b) the CTE in question contains,
>> recursively anywhere inside its rtable or the rtables of any of its
>> nested CTEs, a "self_reference" RTE.

> That's kind of "ugh" too: it sounds expensive, and doing it in a way
> that doesn't produce false positives would be even more complicated.

After further investigation, I concluded that that wasn't that awful,
so done that way.

I'm still not entirely convinced about the behavior for nested WITHs
with different materialization specifications, but that seems like
a separate topic.

			regards, tom lane