Обсуждение: pgsql: Split out tiebreaker comparisons from comparetup_* functions

Split out tiebreaker comparisons from comparetup_* functions

Previously, if a specialized comparator found equal datum1 keys,
the "comparetup" function would repeat the comparison on the
datum before proceeding with the unabbreviated first key
and/or additional sort keys.

Move comparing additional sort keys into "tiebreak" functions so
that specialized comparators can call these directly if needed,
avoiding duplicate work.

Reviewed by David Rowley

Discussion: https://postgr.es/m/CAFBsxsGaVfUrjTghpf%3DkDBYY%3DjWx1PN-fuusVe7Vw5s0XqGdGw%40mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/c9bfa40914be4a0882b904834c2bd32775a50d7b

Modified Files
--------------
src/backend/utils/sort/tuplesort.c         |   9 +--
src/backend/utils/sort/tuplesortvariants.c | 125 ++++++++++++++++++++++-------
src/include/utils/tuplesort.h              |   7 ++
3 files changed, 108 insertions(+), 33 deletions(-)

On Fri, Aug 18, 2023 at 12:48 AM John Naylor
<john.naylor@enterprisedb.com> wrote:
> On Thu, Aug 17, 2023 at 11:41 AM John Naylor <john.naylor@enterprisedb.com> wrote:
> > On Wed, Aug 16, 2023 at 5:17 PM John Naylor <john.naylor@postgresql.org> wrote:
> > >
> > > Split out tiebreaker comparisons from comparetup_* functions
> >
> > Hammerkop is getting OOM errors with this change. Most grand totals in the memory context stats show between 1 and
3MB, and "tuplesort main" only shows small-ish requests, so not sure what's going on. 
>
> That remains the only new failure in the buildfarm, and it just failed in the same way again. I'll try to figure out
whatcould be the cause, but if I don't I'll revert within 24 hours. 

I don't know what's going on on that machine but those two failures
seem different, and there are also now some failures in release
branches that don't have your commit, so I'd wait long for more
evidence...

John Naylor <john.naylor@enterprisedb.com> writes:
> On Fri, Aug 18, 2023 at 5:26 PM Thomas Munro <thomas.munro@gmail.com> wrote:
>> I don't know what's going on on that machine but those two failures
>> seem different, and there are also now some failures in release
>> branches that don't have your commit, so I'd wait long for more
>> evidence...

> Ah, I did check at least one back branch yesterday and didn't see any
> failures then. I see them now, thanks!

... and hamerkop just went back to green on HEAD.  So whatever is up
with that machine, it's not the fault of your commit.

            regards, tom lane