Horton

Re: Early WIP/PoC for inlining CTEs

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Michael Paquier <michael@paquier.xyz>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Robert Haas <robertmhaas@gmail.com>, Andreas Karlsson <andreas@proxel.se>, Andres Freund <andres@anarazel.de>, Thomas Munro <thomas.munro@enterprisedb.com>, Andrew Gierth <andrew@tao11.riddles.org.uk>, David Fetter <david@fetter.org>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2019-01-29T19:52:44Z
Lists: pgsql-hackers

Commits

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  1. Prevent inlining of multiply-referenced CTEs with outer recursive refs.

  2. Allow user control of CTE materialization, and change the default behavior.

  3. Split QTW_EXAMINE_RTES flag into QTW_EXAMINE_RTES_BEFORE/_AFTER.

  4. document when PREPARE uses generic plans

Michael Paquier <michael@paquier.xyz> writes:
> On Mon, Jan 28, 2019 at 05:05:32PM -0500, Tom Lane wrote:
>> Yeah, I thought about that too, but it doesn't seem like an improvement.
>> If the query is very long (which isn't unlikely) I think people would
>> prefer to see the option(s) up front.

> Having these options at the front of the WITH clause looks more
> natural to me.

Well, we've managed to get agreement on the semantics of this thing,
let's not get hung up on the syntax details.

I propose that we implement and document this as

	WITH ctename AS [ MATERIALIZE { ON | OFF } ] ( query )

which is maybe a bit clunky but not awful, and it would leave room
to generalize it to "AS [ optionname optionvalue [ , ... ] ]" if we
ever need to.  Looking at the precedent of e.g. EXPLAIN, we could
probably allow just "MATERIALIZE" as well, with the boolean value
defaulting to true.

			regards, tom lane