Horton

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

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Pg Hackers <pgsql-hackers@postgresql.org>, Corey Huinker <corey.huinker@gmail.com>
Date: 2017-03-20T01:03:51Z
Lists: pgsql-hackers

Attachments

On Sun, Mar 12, 2017 at 3:05 PM, Peter Geoghegan <pg@bowt.ie> wrote:
> I attach my V9 of the patch. I came up some stuff for the design of
> resource management that I think meets every design goal that we have
> for shared/unified BufFiles:

Commit 2609e91fc broke the parallel CREATE INDEX cost model. I should
now pass -1 as the index block argument to compute_parallel_worker(),
just as all callers that aren't parallel index scan do after that
commit. This issue caused V9 to never choose parallel CREATE INDEX
within nbtsort.c. There was also a small amount of bitrot.

Attached V10 fixes this regression. I also couldn't resist adding a
few new assertions that I thought were worth having to buffile.c, plus
dedicated wait events for parallel tuplesort. And, I fixed a silly bug
added in V9 around where worker_wait() should occur.

-- 
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