Horton

Re: POC: converting Lists into arrays

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: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2019-02-26T02:53:26Z
Lists: pgsql-hackers

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On Sun, 24 Feb 2019 at 15:24, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I haven't attempted any performance measurements on this, but at
> least in principle it should speed things up a bit, especially
> for complex test cases involving longer Lists.  I don't have any
> very suitable test cases at hand, anyway.

I've not yet looked at the code, but I thought I'd give this a quick benchmark.

Using the attached patch (as text file so as not to upset the CFbot),
which basically just measures and logs the time taken to run
pg_plan_query. Using this, I ran make installcheck 3 times unpatched
and same again with the patch. I pulled the results of each run into a
spreadsheet and took the average of each of the 3 runs then took the
sum of the total average planning time over the 20334 individual
results.

Results patched atop of 067786cea:

Total average time unpatched:  0.739808667 seconds
Total average time patched:  0.748144333 seconds.

Surprisingly it took 1.13% longer.  I did these tests on an AWS
md5.large instance.

If required, I can send the entire spreadsheet. It's about 750 KB.

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

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.