Horton

Re: Early WIP/PoC for inlining CTEs

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Andreas Karlsson <andreas@proxel.se>, Thomas Munro <thomas.munro@enterprisedb.com>, Andrew Gierth <andrew@tao11.riddles.org.uk>, Tom Lane <tgl@sss.pgh.pa.us>, David Fetter <david@fetter.org>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2019-01-18T20:42:38Z
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 2019-01-18 15:34:46 -0500, Robert Haas wrote:
> On Thu, Jan 17, 2019 at 10:48 AM Andreas Karlsson <andreas@proxel.se> wrote:
> > On 1/11/19 8:10 PM, Robert Haas wrote:
> > > WITH cte_name [[NOT] MATERIALIZED] AS (query) main_query...
> >
> > Hm, when would one want "NOT MATERIALIZED"? I am not sure I see the
> > usefulness of forcing inlining other than if we by default do not inline
> > when a CTE is referenced multiple times.
> 
> When the planner materializes it, but the performance of the resulting
> plan therefore sucks, I suppose.
> 
> I don't feel super-strongly about this, and Tom is right that there
> may be cases where materialization is just not practical due to
> implementation restrictions.

*not* materializing I assume?

Greetings,

Andres Freund