Horton

Re: Early WIP/PoC for inlining CTEs

Merlin Moncure <mmoncure@gmail.com>

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From: Merlin Moncure <mmoncure@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Jeremy Finzel <finzelj@gmail.com>, Andrew Gierth <andrew@tao11.riddles.org.uk>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2019-01-11T21:25:23Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  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, Jul 24, 2018 at 6:10 PM Andres Freund <andres@anarazel.de> wrote:
> My read of the concensus (in which I am in the majority, so I might be
> biased) is that we do want inlining to be the default. We were thinking
> that it'd be necessary to provide a way to force inlining on the SQL
> level for individual CTEs.

This is correct.  Suggesting that we need syntax to disabling inlining
at the CTE level, and/or GUC to control the behavior (which I agree
should be defualted to inline).  Something like
enable_cte_inline=true; I'm not very enthusiastic about explicitly
breaking intentionally introduced optimization fences and then forcing
people to inject our OFFSET 0 hack.   This is just too unpleasant to
contemplate...what  happens if we come up with a better implemntation
of OFFSET?  yuck.

Thanks for providing this, CTE plan problems are a real bugaboo.

merlin