Horton

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

James Coleman <jtc331@gmail.com>

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From: James Coleman <jtc331@gmail.com>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Justin Pryzby <pryzby@telsasoft.com>, Tom Lane <tgl@sss.pgh.pa.us>, Alvaro Herrera <alvherre@2ndquadrant.com>, Michael Paquier <michael@paquier.xyz>, Rafia Sabih <rafia.pghackers@gmail.com>, Peter Geoghegan <pg@bowt.ie>, Simon Riggs <simon@2ndquadrant.com>, Shaun Thomas <shaun.thomas@2ndquadrant.com>, Dmitry Dolgov <9erthalion6@gmail.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Andreas Karlsson <andreas@proxel.se>
Date: 2020-04-08T00:04:46Z
Lists: pgsql-hackers 
On Tue, Apr 7, 2020 at 7:58 PM Tomas Vondra
<tomas.vondra@2ndquadrant.com> wrote:
>
> On Tue, Apr 07, 2020 at 07:50:26PM -0400, James Coleman wrote:
> >On Tue, Apr 7, 2020 at 7:02 PM Tomas Vondra
> ><tomas.vondra@2ndquadrant.com> wrote:
> >>
> >> On Mon, Apr 06, 2020 at 11:25:21PM -0500, Justin Pryzby wrote:
> >> >On Mon, Apr 06, 2020 at 09:57:22PM +0200, Tomas Vondra wrote:
> >> >> I've pushed the fist part of this patch series - I've reorganized it a
> >> >
> >> >I scanned through this again post-commit.  Find attached some suggestions.
> >> >
> >>
> >> Thanks. The typo fixes seem clear, except for this bit:
> >>
> >>    * If we've set up either of the sort states yet, we need to reset them.
> >>    * We could end them and null out the pointers, but there's no reason to
> >>    * repay the setup cost, and because ???? guard setting up pivot comparator
> >>    * state similarly, doing so might actually cause a leak.
> >>
> >> I can't figure out what ???? should be. James, do you recall what this
> >> should be?
> >
> >Yep, it's ExecIncrementalSort. If you look for the block guarded by
> >`if (fullsort_state == NULL)` you'll see the call to
> >preparePresortedCols(), which sets up the pivot comparator state
> >referenced by this comment.
> >
>
> OK, so it should be "... and because ExecIncrementalSort guard ..."?

Yes, "because ExecIncrementalSort guards presorted column functions by
checking to see if the full sort state has been initialized yet,
setting the sort states to null here might cause..." (that's more
specific IMO than my original "pivot comparator state...doing so").

James

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.