Horton

Re: A qsort template

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: John Naylor <john.naylor@enterprisedb.com>
Cc: Thomas Munro <thomas.munro@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2022-01-19T02:57:45Z
Lists: pgsql-hackers 
On Tue, Jan 18, 2022 at 6:39 PM John Naylor
<john.naylor@enterprisedb.com> wrote:
> Editorializing the null position in queries is not very common in my
> experience. Not null is interesting since it'd be trivial to pass
> constant false to the same Apply[XYZ]SortComparator() and let the
> compiler remove all those branches for us. On the other hand, those
> branches would be otherwise predicted well, so it might make little or
> no difference.

If you were going to do this, maybe you could encode NULL directly in
an abbreviated key. I think that that could be made to work if it was
limited to opclasses with abbreviated keys encoded as unsigned
integers. Just a thought.

-- 
Peter Geoghegan

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.