Horton

Re: pgsql: Add parallel-aware hash joins.

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>, pgsql-committers <pgsql-committers@postgresql.org>
Date: 2018-01-04T01:23:05Z
Lists: pgsql-hackers 
Hi,

On 2018-01-03 20:17:04 -0500, Tom Lane wrote:
> So this patch has been in place for two weeks, the buildfarm has still
> got the measles, and we're entering the January commitfest with a lot
> of other work to get done.  I realize that the two weeks were mostly
> holiday time, but it's time to have some urgency about clearing the
> buildfarm failures.

Agreed.


> As best I understand, the remaining failures simply arise from
> an unstable regression test case and aren't teaching us anything
> of value.

I think that's the correct interpretation.


> I propose that for the moment, we simply remove the
> failing query from join.sql.  We can put it back when there's
> reason to think it will pass everywhere.

Alternatively we could temporarily push an alternative output. It
doesn't seem inconceivable we missed an actual bug due to the
noise. Don't have a strong opinion on which of the two to choose.

Unless somebody does something first, I'll disable the test tomorrow
pacific morning. But perhaps Thomas can up with an approach till then
that seems likely to pass on the different architectures. Seems quite
possible to just adjust the thresholds carefully?


Greetings,

Andres Freund

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.