"David G. Johnston" <david.g.johnston@gmail.com> writes:
> v12 what?
That ...
> It would help if you can provide a self-contained demonstration
> that others can then verify and debug (or explain).
... and that. As this message stands, it's undocumented whining.
Please see
https://wiki.postgresql.org/wiki/Slow_Query_Questions
for the sort of information we need to debug performance issues.
There's also
https://wiki.postgresql.org/wiki/Guide_to_reporting_problems
although that's not oriented specifically to performance issues.
(I recall that we have fixed some problems in the past that could
lead to unreasonable numbers of temp files in hash joins. Whether
there's more to do, or Peter is running a version that lacks those
fixes, is impossible to tell with the given info.)
regards, tom lane
