Horton

Re: POC: converting Lists into arrays

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: Jesper Pedersen <jesper.pedersen@redhat.com>, Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2019-07-21T14:45:32Z
Lists: pgsql-hackers 
David Rowley <david.rowley@2ndquadrant.com> writes:
> On Wed, 17 Jul 2019 at 11:06, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> (Actually, I doubt that any of these changes will really move the
>> performance needle in the real world.  It's more a case of wanting
>> the code to present good examples not bad ones.)

> In spirit with the above, I'd quite like to fix a small bad example
> that I ended up with in nodeAppend.c and nodeMergeappend.c for
> run-time partition pruning.

I didn't test the patch, but just by eyeball it looks sane,
and I concur it should win if the bitmap is sparse.

One small question is whether it loses if most of the subplans
are present in the bitmap.  I imagine that would be close enough
to break-even, but it might be worth trying to test to be sure.
(I'd think about breaking out just the loops in question and
testing them stand-alone, or else putting in an outer loop to
repeat them, since as you say the surrounding work probably
dominates.)

			regards, tom lane

Commits

  1. Remove EState.es_range_table_array.

  2. Rationalize use of list_concat + list_copy combinations.

  3. Cosmetic improvements in setup of planner's per-RTE arrays.

  4. Make better use of the new List implementation in a couple of places

  5. Fix sepgsql test results for commit d97b714a2.

  6. Avoid using lcons and list_delete_first where it's easy to do so.

  7. Remove lappend_cell...() family of List functions.

  8. Clean up some ad-hoc code for sorting and de-duplicating Lists.

  9. Redesign the API for list sorting (list_qsort becomes list_sort).

  10. Remove dead code.

  11. Represent Lists as expansible arrays, not chains of cons-cells.

  12. Standardize some more loops that chase down parallel lists.

  13. Reimplement the linked list data structure used throughout the backend.