Horton

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

Peter Geoghegan <pg@heroku.com>

View thread View on postgr.es
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: 2016-12-21T21:48:09Z
Lists: pgsql-hackers 
On Wed, Dec 21, 2016 at 10:21 AM, Peter Geoghegan <pg@heroku.com> wrote:
> On Wed, Dec 21, 2016 at 6:00 AM, Robert Haas <robertmhaas@gmail.com> wrote:
>> 3. Just live with the waste of space.
>
> I am loathe to create a special case for the parallel interface too,
> but I think it's possible that *no* caller will ever actually need to
> live with this restriction at any time in the future.

I just realized that you were actually talking about the waste of
space in workers here, as opposed to the theoretical waste of space
that would occur in the leader should there ever be a parallel
randomAccess tuplesort caller.

To be clear, I am totally against allowing a waste of logtape.c temp
file space in *workers*, because that implies a cost that will most
certainly be felt by users all the time.

-- 
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