Horton

Re: [PATCH] Incremental sort

Alexander Korotkov <a.korotkov@postgrespro.ru>

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From: Alexander Korotkov <a.korotkov@postgrespro.ru>
To: Andres Freund <andres@anarazel.de>
Cc: David Steele <david@pgmasters.net>, Heikki Linnakangas <hlinnaka@iki.fi>, Mithun Cy <mithun.cy@enterprisedb.com>, Robert Haas <robertmhaas@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-04-03T21:04:09Z
Lists: pgsql-hackers 
On Mon, Apr 3, 2017 at 10:05 PM, Andres Freund <andres@anarazel.de> wrote:

> On April 3, 2017 12:03:56 PM PDT, Alexander Korotkov <
> a.korotkov@postgrespro.ru> wrote:
> >On Mon, Apr 3, 2017 at 9:34 PM, Andres Freund <andres@anarazel.de>
> >wrote:
> >
> >> On 2017-03-29 00:17:02 +0300, Alexander Korotkov wrote:
> >> > On Tue, Mar 28, 2017 at 5:27 PM, David Steele <david@pgmasters.net>
> >> wrote:
> >> > > On 3/20/17 10:19 AM, Heikki Linnakangas wrote:
> >> > >
> >> > >> On 03/20/2017 11:33 AM, Alexander Korotkov wrote:
> >> > >>
> >> > >>> Please, find rebased patch in the attachment.
> >> > >>>
> >> > >>
> >> > >> I had a quick look at this.
> >> > >>
> >> > >
> >> > > <...>
> >> > >
> >> > > According to 'perf', 85% of the CPU time is spent in
> >ExecCopySlot(). To
> >> > >> alleviate that, it might be worthwhile to add a special case for
> >when
> >> > >> the group contains exactly one group, and not put the tuple to
> >the
> >> > >> tuplesort in that case. Or if we cannot ensure that the
> >Incremental
> >> Sort
> >> > >> is actually faster, the cost model should probably be smarter,
> >to
> >> avoid
> >> > >> picking an incremental sort when it's not a win.
> >> > >>
> >> > >
> >> > > This thread has been idle for over a week.  Please respond with a
> >new
> >> > > patch by 2017-03-30 00:00 AoE (UTC-12) or this submission will be
> >> marked
> >> > > "Returned with Feedback".
> >>
> >> > Thank you for reminder!
> >>
> >> I've just done so.  Please resubmit once updated, it's a cool
> >feature.
> >>
> >
> >Thank you!
> >I already sent version of patch after David's reminder.
> >Please find rebased patch in the attachment.
>
> Cool. I think that's still a bit late for v10?
>

I don't know.  ISTM, that I addressed all the issues raised by reviewers.
Also, this patch is pending since late 2013.  It would be very nice to
finally get it in...

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company

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.