Horton

Re: [HACKERS] Parallel tuplesort (for parallel B-Tree index creation)

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Rushabh Lathia <rushabh.lathia@gmail.com>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>, Robert Haas <robertmhaas@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Pg Hackers <pgsql-hackers@postgresql.org>, Corey Huinker <corey.huinker@gmail.com>
Date: 2017-11-15T18:39:58Z
Lists: pgsql-hackers 
On Tue, Nov 14, 2017 at 10:01 AM, Peter Geoghegan <pg@bowt.ie> wrote:
> On Tue, Nov 14, 2017 at 1:41 AM, Rushabh Lathia
> <rushabh.lathia@gmail.com> wrote:
>> Thanks Peter and Thomas for the review comments.
>
> No problem. More feedback:

I see that Robert just committed support for a
parallel_leader_participation GUC. Parallel tuplesort should use this,
too.

It will be easy to adopt the patch to make this work. Just change the
code within nbtsort.c to respect parallel_leader_participation, rather
than leaving that as a compile-time switch. Remove the
force_single_worker variable, and use !parallel_leader_participation
in its place.

The parallel_leader_participation docs will also need to be updated.

-- 
Peter Geoghegan

Commits

  1. Support parallel btree index builds.

  2. Report an ERROR if a parallel worker fails to start properly.

  3. Transfer state pertaining to pending REINDEX operations to workers.

  4. Add a barrier primitive for synchronizing backends.

  5. Allow DML commands that create tables to use parallel query.

  6. Refactor GetOldestXmin() to use flags

  7. Fix regression in parallel planning against inheritance tables.

  8. Don't create "holes" in BufFiles, in the new logtape code.

  9. Simplify the code for logical tape read buffers.

  10. Fix excessive memory consumption in the new sort pre-reading code.

  11. Implement binary heap replace-top operation in a smarter way.

  12. Cosmetic code cleanup in commands/extension.c.

  13. Speed up planner's scanning for parallel-query hazards.

  14. Read from the same worker repeatedly until it returns no tuple.

  15. Improve tuplesort.c to support variable merge order. The original coding