Horton

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

Peter Geoghegan <pg@heroku.com>

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From: Peter Geoghegan <pg@heroku.com>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Robert Haas <robertmhaas@gmail.com>, Pg Hackers <pgsql-hackers@postgresql.org>, Corey Huinker <corey.huinker@gmail.com>
Date: 2016-09-06T19:42:42Z
Lists: pgsql-hackers 
On Tue, Sep 6, 2016 at 12:39 PM, Peter Geoghegan <pg@heroku.com> wrote:
> On Tue, Sep 6, 2016 at 12:08 AM, Heikki Linnakangas <hlinnaka@iki.fi> wrote:
>>> I attach a patch that changes how we maintain the heap invariant
>>> during tuplesort merging.
>
>> Nice!
>
> Thanks!

BTW, the way that k-way merging is made more efficient by this
approach makes the case for replacement selection even weaker than it
was just before we almost killed it. I hate to say it, but I have to
wonder if we shouldn't get rid of the new-to-9.6
replacement_sort_tuples because of this, and completely kill
replacement selection. I'm not going to go on about it, but that seems
sensible to me.


-- 
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