Horton

Re: [PATCH] Incremental sort (was: PoC: Partial sort)

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: James Coleman <jtc331@gmail.com>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>, Simon Riggs <simon@2ndquadrant.com>, Rafia Sabih <rafia.pghackers@gmail.com>, Shaun Thomas <shaun.thomas@2ndquadrant.com>, Dmitry Dolgov <9erthalion6@gmail.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>, Tom Lane <tgl@sss.pgh.pa.us>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2019-06-25T19:13:01Z
Lists: pgsql-hackers 
On Tue, Jun 25, 2019 at 11:03 AM James Coleman <jtc331@gmail.com> wrote:
> No, I haven't confirmed that it's called less frequently, and I'd be
> extremely surprised if it were given the diff doesn't suggest any
> changes to that at all.

I must have misunderstood, then. I thought that you were suggesting
that that might have happened.

> If you think it's important enough to do so, I can instrument it to
> confirm, but I was mostly wanting to know if there were any other
> plausible explanations, and I think you've provided one: there *are*
> changes in the patch to memory contexts in tuplesort.c, so if memory
> fragmentation is a real concern this patch could definitely notice
> changes in that regard.

Sounds like it's probably fragmentation. That's generally hard to measure.

-- 
Peter Geoghegan

Commits

  1. Further adjustments to Hashagg EXPLAIN ANALYZE output

  2. Rework EXPLAIN format for incremental sort

  3. Fix typos and improve incremental sort comments

  4. Stabilize incremental_sort tests

  5. Minor improvements in Incremental Sort explain

  6. Consider Incremental Sort paths at additional places

  7. Fix representation of SORT_TYPE_STILL_IN_PROGRESS.

  8. Fix failures in incremental_sort due to number of workers

  9. Fix show_incremental_sort_info with force_parallel_mode

  10. Implement Incremental Sort

  11. Fix handling of "Subplans Removed" field in EXPLAIN output.

  12. Fix EXPLAIN (SETTINGS) to follow policy about when to print empty fields.

  13. Ensure plpgsql result tuples have the right composite type marking.

  14. Propagate sort instrumentation from workers back to leader.

  15. Make new regression test case parallel-safe, and improve its output.

  16. Push limit through subqueries to underlying sort, where possible.

  17. Fix inappropriate printing of never-measured times in EXPLAIN.

  18. Fix some infelicities in EXPLAIN output for parallel query plans.