Horton

Re: A qsort template

John Naylor <john.naylor@enterprisedb.com>

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From: John Naylor <john.naylor@enterprisedb.com>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Thomas Munro <thomas.munro@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2022-04-02T08:50:17Z
Lists: pgsql-hackers 
I wrote:

> I started towards incorporating the change in insertion sort threshold
> (part of 0010), but that caused regression test failures, so that will
> have to wait for a bit of analysis and retesting. (My earlier tests
> were done in a separate module.)

The failures seem to be where sort order is partially specified. E.g.
ORDER BY col_a, where there are duplicates there and other columns are
different. Insertion sort is stable IIRC, so moving the threshold
caused different orders in these cases. Some cases can be conveniently
fixed with additional columns in the ORDER BY clause. I'll go through
the failures and see how much can be cleaned up as a preparatory
refactoring.

-- 
John Naylor
EDB: http://www.enterprisedb.com

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.