Horton

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

Thomas Munro <thomas.munro@enterprisedb.com>

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From: Thomas Munro <thomas.munro@enterprisedb.com>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Rushabh Lathia <rushabh.lathia@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Pg Hackers <pgsql-hackers@postgresql.org>, Corey Huinker <corey.huinker@gmail.com>
Date: 2018-01-10T03:36:20Z
Lists: pgsql-hackers 
On Sat, Jan 6, 2018 at 11:17 AM, Peter Geoghegan <pg@bowt.ie> wrote:
> * Significant overhaul of tuplesort.h contract. This had references to
> the old approach, and to tqueue.c's tuple descriptor thing that was
> since superseded by the typmod registry added for parallel hash join.
> These were updated/removed.

+1

> * Both tuplesort.c and logtape.c now say that they cannot write to the
> writable/last tape, while still acknowledging that it is in fact the
> leader tape, and that this restriction is due to a restriction with
> BufFiles. They also point out that if the restriction within buffile.c
> ever was removed, everything would work fine.

+1

> * Added new call to BufFileExportShared() when freezing tape in logtape.c.

+1

> * Polished the stuff that is added to buffile.c. Mostly comments that
> clarify its reason for existing. Also added Assert()s.

+1

This looks good to me.

-- 
Thomas Munro
http://www.enterprisedb.com

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