Horton

Re: A qsort template

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: John Naylor <john.naylor@enterprisedb.com>
Cc: Thomas Munro <thomas.munro@gmail.com>, Andres Freund <andres@anarazel.de>, Justin Pryzby <pryzby@telsasoft.com>, Peter Geoghegan <pg@bowt.ie>, pgsql-hackers <pgsql-hackers@postgresql.org>, Robert Haas <rhaas@postgresql.org>
Date: 2022-04-14T06:46:00Z
Lists: pgsql-hackers

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On Wed, 13 Apr 2022 at 23:19, John Naylor <john.naylor@enterprisedb.com> wrote:
> More broadly than the regression, Thomas' is very often the fastest of
> all, at the cost of more binary size. David's is occasionally slower
> than v15 or v15 with revert, but much of that is a slight difference
> and some is probably noise.

Just to get an opinion from some other hardware, I've run your test
script on my AMD 3990x machine.

My opinion here is that the best thing we can learn from both of our
results is, do the patches fix the regression?

I don't believe it should be about if adding the additional
specializations performs better than skipping the tie break function
call.  I think it's pretty obvious that the specializations will be
faster.  I think if it was decided that v16 would be the version where
more work should be done to decide on what should be specialized and
what shouldn't be, then we shouldn't let this regression force our
hand to make that choice now. It'll be pretty hard to remove any
specializations once they've been in a released version of Postgres.

David

Commits

  1. Remove debug messages from tuplesort_sort_memtuples()

  2. Fix performance regression in tuplesort specializations

  3. Fix tuplesort optimization for CLUSTER-on-expression.

  4. Initial pgindent and pgperltidy run for v14.

  5. Specialize checkpointer sort functions.

  6. Use sort_template.h for qsort() and qsort_arg().

  7. Use sort_template.h for qsort_tuple() and qsort_ssup().

  8. Add sort_template.h for making sort functions.

  9. Use abbreviated keys for faster sorting of text datums.