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: Robert Haas <robertmhaas@gmail.com>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Pg Hackers <pgsql-hackers@postgresql.org>, Corey Huinker <corey.huinker@gmail.com>
Date: 2016-09-26T19:40:05Z
Lists: pgsql-hackers 
On Mon, Sep 26, 2016 at 6:58 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>> That requires some kind of mutual exclusion mechanism, like an LWLock.
>
> No, it doesn't.  Shared memory queues are single-reader, single-writer.

The point is that there is a natural dependency when merging is
performed eagerly within the leader. One thing needs to be in lockstep
with the others. That's all.


-- 
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