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: Robert Haas <robertmhaas@gmail.com>
Cc: Peter Geoghegan <pg@bowt.ie>, Amit Kapila <amit.kapila16@gmail.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: 2018-01-23T22:08:53Z
Lists: pgsql-hackers 
On Fri, Jan 19, 2018 at 6:22 AM, Robert Haas <robertmhaas@gmail.com> wrote:
>> (3)
>> erm, maybe it's a problem that errors occurring in workers while the
>> leader is waiting at a barrier won't unblock the leader (we don't
>> detach from barriers on abort/exit) -- I'll look into this.
>
> I think if there's an ERROR, the general parallelism machinery is
> going to arrange to kill every worker, so nothing matters in that case
> unless barrier waits ignore interrupts, which I'm pretty sure they
> don't.  (Also: if they do, I'll hit the ceiling; that would be awful.)

(After talking this through with Robert off-list).  Right, the
CHECK_FOR_INTERRUPTS() in ConditionVariableSleep() handles errors from
parallel workers.  There is no problem here.

-- 
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