Re: pgstat: allow a stats kind to use its own dedicated dsa/dshash

Say folks,

The currently committed version of test_custom_stats is unstable
on my BF animal mamba [1].

Running the test by hand 30 times on that machine, I got 20 passes,
7 runs that failed at line 94 only, and 3 that duplicated the
buildfarm report:

# Failed test 'variable-sized stats of entry1 for test_custom_var_stats'
# at t/001_custom_stats.pl line 94.
# got: 'entry1|0|Test entry 1'
# expected: 'entry1|2|Test entry 1'

# Failed test 'variable-sized stats of entry2 for test_custom_var_stats'
# at t/001_custom_stats.pl line 100.
# got: 'entry2|0|Test entry 2'
# expected: 'entry2|3|Test entry 2'

What it looks like to me is that the test script makes no attempt to
force the locally-applied stats out to shared memory, and the relative
failure rates here correspond to the probability that we can
execute 1, 2, or more test_custom_stats_var_report() queries before
a background stats flush happens. If that's a correct diagnosis,
we'll probably see this on other slow animals before too much longer.
Otherwise, maybe there's something happening here that's specific
to PPC and/or NetBSD?

regards, tom lane

[1] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=mamba&dt=2026-10-17%2006%3A12%3A12