Horton

Re: A qsort template

Thomas Munro <thomas.munro@gmail.com>

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From: Thomas Munro <thomas.munro@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Justin Pryzby <pryzby@telsasoft.com>, John Naylor <john.naylor@enterprisedb.com>, Peter Geoghegan <pg@bowt.ie>, pgsql-hackers <pgsql-hackers@postgresql.org>, Robert Haas <rhaas@postgresql.org>
Date: 2022-04-02T21:45:13Z
Lists: pgsql-hackers

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On Sun, Apr 3, 2022 at 9:03 AM Andres Freund <andres@anarazel.de> wrote:
> It's certainly not pretty that copytup_cluster() can use SortTuples without
> actually using SortTuples. Afaics it basically only computes isnull1/datum1 if
> state->indexInfo->ii_IndexAttrNumbers[0] == 0.

I think we just need to decide up front if we're in a situation that
can't provide datum1/isnull1 (in this case because it's an expression
index), and skip the optimised paths.  Here's an experimental patch...
still looking into whether there are more cases like this...

(There's also room to recognise when you don't even need to look at
isnull1 for a less branchy optimised sort, but that was already
discussed and put off for later.)

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.