Horton

Re: pgsql: Add parallel-aware hash joins.

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Andres Freund <andres@anarazel.de>, pgsql-committers <pgsql-committers@postgresql.org>
Date: 2017-12-28T04:26:35Z
Lists: pgsql-hackers 
Thomas Munro <thomas.munro@enterprisedb.com> writes:
> On Thu, Dec 28, 2017 at 3:32 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Aside from the instability problems, I'm pretty unhappy about how much
>> the PHJ patch has added to the runtime of "make check".  I do not think
>> any one feature can justify adding 20% to that.  Can't you cut down the
>> amount of data processed by these new test cases?

> Isn't that mostly because of the CV livelock problem?

Hm, maybe.  I quoted the 20% figure on the basis of longfin's reports,
not prairiedog's ... but it might be seeing some of the livelock effect
too.

> So without the effects of that bug it's only taking 2.4% longer than
> commit fa330f9a.  Is that acceptable for a feature of this size and
> complexity?  I will also look into making the data sets smaller.

That sounds better, but it's still worth asking whether the tests
could be quicker.

			regards, tom lane

Commits

  1. Update obsolete sentence in README.parallel.

  2. Rewrite ConditionVariableBroadcast() to avoid live-lock.

  3. Tweak parallel hash join test case in hopes of improving stability.

  4. Rename pg_rewind's copy_file_range() to avoid conflict with new linux syscall.

  5. Fix some minor errors in new PHJ code.

  6. Fix EXPLAIN ANALYZE output for Parallel Hash.

  7. Fix rare assertion failure in parallel hash join.

  8. Cancel CV sleep during subtransaction abort.

  9. Add parallel-aware hash joins.

  10. Fix EXPLAIN ANALYZE of hash join when the leader doesn't participate.

  11. Add some regression tests that exercise hash join code.