Re: Early WIP/PoC for inlining CTEs

Robert Haas <robertmhaas@gmail.com>

From: Robert Haas <robertmhaas@gmail.com>

To: Andres Freund <andres@anarazel.de>

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: 2019-01-18T20:44:46Z

Lists: pgsql-hackers

Commits

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Prevent inlining of multiply-referenced CTEs with outer recursive refs.
- 9476131278c7 12.0 landed
Allow user control of CTE materialization, and change the default behavior.
- 608b167f9f9c 12.0 landed
Split QTW_EXAMINE_RTES flag into QTW_EXAMINE_RTES_BEFORE/_AFTER.
- 18c0da88a5d9 12.0 landed
document when PREPARE uses generic plans
- fab9d1da4a21 9.6.0 cited

On Fri, Jan 18, 2019 at 3:42 PM Andres Freund <andres@anarazel.de> wrote:
> 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?

Right, sorry.

-- 
Robert Haas
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