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: Robert Haas <robertmhaas@gmail.com>
Cc: 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: 2018-01-18T19:05:32Z
Lists: pgsql-hackers 
On Thu, Jan 18, 2018 at 10:17 AM, Robert Haas <robertmhaas@gmail.com> wrote:
>> Should I go ahead and restore builds on catalogs, and remove those
>> comments, on the assumption that your patch will be committed before
>> mine? Obviously parallel index builds on catalogs don't matter. OTOH,
>> why not? Perhaps it's like the debate around HOT that took place over
>> 10 years ago, where Tom insisted that HOT work with catalogs on
>> general principle.
>
> Yes, I think so.  If you (or someone else) can review that patch, I'll
> go ahead and commit it, and then your patch can treat it as a solved
> problem.  I'm not really worried about the cycles; the amount of
> effort required here is surely very small compared to all of the other
> things that have to be done when starting a parallel worker.

Review of your patch:

* SerializedReindexState could use some comments. At least a one liner
stating its basic purpose.

* The "System index reindexing support" comment block could do with a
passing acknowledgement of the fact that this is serialized for
parallel workers.

* Maybe the "Serialize reindex state" comment within
InitializeParallelDSM() should instead say something like "Serialize
indexes-pending-reindex state".

Other than that, looks good to me. It's a simple patch with a clear purpose.

-- 
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