Re: SELECT creates millions of temp files in a single directory

"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