Horton

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

Tomas Vondra <tomas.vondra@2ndquadrant.com>

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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Andres Freund <andres@anarazel.de>, 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: 2018-02-06T22:21:15Z
Lists: pgsql-hackers 

On 02/06/2018 10:39 PM, Peter Geoghegan wrote:
> On Tue, Feb 6, 2018 at 1:30 PM, Tomas Vondra
> <tomas.vondra@2ndquadrant.com> wrote:
>> I have little idea what -Og exactly means. It seems to be focused on
>> debugging experience, and so still does some of the optimizations.
> 
> As I understand it, -Og allows any optimization that does not hamper
> walking through code with a debugger.
> 
>> Which
>> I think would explain why skink was not detecting some of the failures
>> for a long time.
> 
> I think that skink didn't detect failures until now because the code
> wasn't exercised until parallel CREATE INDEX was added, simply because
> the function LogicalTapeFreeze() was never reached (though that's not
> the only reason, it is the most obvious one).
> 

Maybe. What I had in mind was a different thread from November,
discussing some non-deterministic valgrind failures:

https://www.postgresql.org/message-id/flat/20171125200014.qbewtip5oydqsklt%40alap3.anarazel.de#20171125200014.qbewtip5oydqsklt@alap3.anarazel.de

But you're right that may be irrelevant here. As I said, it was mostly
just a random comment about valgrind.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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