Horton

Re: Early WIP/PoC for inlining CTEs

Merlin Moncure <mmoncure@gmail.com>

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From: Merlin Moncure <mmoncure@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Michael Paquier <michael@paquier.xyz>, 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: 2019-01-29T20:36:31Z
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

On Tue, Jan 29, 2019 at 1:53 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> 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.

I hate to bikeshed here, but I think it's better english using that
style of syntax to say,
 WITH ctename AS [ MATERIALIZATION { ON | OFF } ] ( query )

merlin