Horton

Re: A qsort template

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Thomas Munro <thomas.munro@gmail.com>
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: 2022-04-02T23:11:51Z
Lists: pgsql-hackers 
Hi,

On 2022-04-03 09:45:13 +1200, Thomas Munro wrote:
> 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...

That's a lot of redundant checks. How about putting all the checks for
optimized paths into one if (state->sortKeys && !state->disable_datum1)?

I'm a bit worried that none of the !ubsan tests failed on this...

Greetings,

Andres Freund

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.