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: Bruce Momjian <bruce@momjian.us>, Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2019-06-14T02:32:23Z
Lists: pgsql-hackers 
David Rowley <david.rowley@2ndquadrant.com> writes:
> On Fri, 14 Jun 2019 at 13:54, Bruce Momjian <bruce@momjian.us> wrote:
>> Have you tested the performance impact?

> I did some and posted earlier in the thread:
> https://postgr.es/m/CAKJS1f8h2vs8M0cgFsgfivfkjvudU5-MZO1gJB2uf0m8_9VCpQ@mail.gmail.com

> It came out only slightly slower over the whole regression test run,
> which I now think is surprisingly good considering how much we've
> tuned the code over the years with the assumption that List is a
> singly linked list.  We'll be able to get rid of things like
> PlannerInfo's simple_rte_array and append_rel_array along with
> EState's es_range_table_array.

Yeah.  I have not made any attempt at all in the current patch to
re-tune the code, or clean up places that are maintaining parallel
Lists and arrays (such as the ones David mentions).  So it's not
entirely fair to take the current state of the patch as representative
of where performance would settle once we've bought into the new
method.

			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.