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: Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Thomas Munro <thomas.munro@enterprisedb.com>, Rushabh Lathia <rushabh.lathia@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Pg Hackers <pgsql-hackers@postgresql.org>, Corey Huinker <corey.huinker@gmail.com>
Date: 2018-02-03T00:31:50Z
Lists: pgsql-hackers 
On Fri, Feb 2, 2018 at 1:58 PM, Andres Freund <andres@anarazel.de> wrote:
> Not saying you're wrong, but you should include a comment on why this is
> a benign warning. Presumably it's some padding memory somewhere, but
> it's not obvious from the above bleat.

Sure. This looks slightly more complicated than first anticipated, but
I'll keep everyone posted.

Valgrind suppression aside, this raises another question. The stack
trace shows that the error happens during the creation of a new TOAST
table (CheckAndCreateToastTable()). I wonder if I should also pass
down a flag that makes sure that parallelism is never even attempted
from that path, to match TRUNCATE's suppression of parallel index
builds during its reindexing. It really shouldn't be a problem as
things stand, but maybe it's better to be consistent about "useless"
parallel CREATE INDEX attempts, and suppress them here too.

-- 
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