Horton

Re: why partition pruning doesn't work?

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Rowley <david.rowley@2ndquadrant.com>
Cc: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, Dmitry Dolgov <9erthalion6@gmail.com>, Jeff Janes <jeff.janes@gmail.com>, Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>, Pavel Stehule <pavel.stehule@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2018-06-08T03:22:51Z
Lists: pgsql-hackers 
David Rowley <david.rowley@2ndquadrant.com> writes:
> On 8 June 2018 at 03:43, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Maybe there's something I'm missing here, but I sort of hoped that this
>> patch would nuke all the special-case code for Params in this area.
>> Why is there any need to distinguish them from other stable expressions?

> We need to know which Params exist in the Expr as if there are no
> Params, or only external Params, then we can run-time prune during
> startup of the executor.

This does not refute my question.  Why doesn't the same logic apply
to any stable expression?  That is, ISTM a Param is a special case
of that.

			regards, tom lane

Commits

  1. Fix up run-time partition pruning's use of relcache's partition data.

  2. Fix access to just-closed relcache entry.

  3. Improve ExecFindInitialMatchingSubPlans's subplan renumbering logic.

  4. Improve commentary about run-time partition pruning data structures.

  5. Fix run-time partition pruning code to handle NULL values properly.

  6. Assorted cosmetic cleanup of run-time-partition-pruning code.

  7. Relocate partition pruning structs to a saner place.

  8. Improve run-time partition pruning to handle any stable expression.

  9. Support partition pruning at execution time