Horton

Re: why partition pruning doesn't work?

David Rowley <david.rowley@2ndquadrant.com>

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From: David Rowley <david.rowley@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
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: 2018-06-10T13:11:33Z
Lists: pgsql-hackers

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On 10 June 2018 at 09:00, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I wrote:
>> One thing I'm wondering about is why in the world are PartitionPruneInfo
>> and its subsidiary struct types declared in primnodes.h?

That may have been a legacy thing that accidentally wasn't changed
from a previous version of the patch. I've now moved it to
plannodes.h.

> Oh, and while I'm bitching: it seems like there is hardly any part of
> the partitioning code in which the comments aren't desperately in need
> of a copy-editing pass.  They are just chock-full of misspellings,
> grammar that is faulty enough to make the meaning unclear, and/or
> errors of fact.  An example of the latter is the repeated claims that
> the basic partitioning functions belong to the planner.  Maybe that
> was true at some stage of development; but AFAICS the logic in question
> now lives in src/backend/partitioning/, which I would not think is
> part of the planner.

I've made a pass over the execPartition.c and partprune.c code
attempting to resolve these issues.  I have hopefully fixed them all,
but I apologise if I've missed any.

I also couldn't resist making a few other improvements to the code.

-- 
 David Rowley                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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