Horton

Re: [PATCH] Incremental sort

Alexander Korotkov <a.korotkov@postgrespro.ru>

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From: Alexander Korotkov <a.korotkov@postgrespro.ru>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Mithun Cy <mithun.cy@enterprisedb.com>, Robert Haas <robertmhaas@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-04-26T17:35:04Z
Lists: pgsql-hackers 
On Wed, Apr 26, 2017 at 8:20 PM, Peter Geoghegan <pg@bowt.ie> wrote:

> On Wed, Apr 26, 2017 at 10:10 AM, Alexander Korotkov
> <a.korotkov@postgrespro.ru> wrote:
> > OK, I get it.  Our qsort is so fast not only on 100% presorted case.
> > However, that doesn't change many things in context of incremental sort.
>
> The important point is to make any presorted test case only ~99%
> presorted, so as to not give too much credit to the "high risk"
> presort check optimization.
>
> The switch to insertion sort that we left in (not the bad one removed
> by a3f0b3d -- the insertion sort that actually comes from the B&M
> paper) does "legitimately" make sorting faster with presorted cases.


I'm still focusing on making incremental sort not slower than qsort with
presorted optimization.  Independently on whether this is "high risk"
optimization or not...
However, adding more test cases is always good.

------
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.