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: Tomas Vondra <tomas.vondra@2ndquadrant.com>
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: 2018-02-06T21:14:26Z
Lists: pgsql-hackers 
On Tue, Feb 6, 2018 at 1:04 PM, Tomas Vondra
<tomas.vondra@2ndquadrant.com> wrote:
> Did you do a test with "-O0"? In my experience that makes valgrind tests
> much more reliable and repeatable. Some time ago we've seen cases that
> were failing for me but not for others, and I suspect it was due to me
> using "-O0".

FWIW, I use -O1 when configure is run for Valgrind. I also turn off
assertions (this is all scripted). According to the Valgrind manual:

"With -O1 line numbers in error messages can be inaccurate, although
generally speaking running Memcheck on code compiled at -O1 works
fairly well, and the speed improvement compared to running -O0 is
quite significant. Use of -O2 and above is not recommended as Memcheck
occasionally reports uninitialised-value errors which don’t really
exist."

The manual does also say that there might even be some problems with
-O1 at a later point, but it sounds like it's probably worth it to me.
Skink uses -Og, FWIW.

-- 
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