Re: identifying the backend that owns a temporary schema

Nathan Bossart <nathandbossart(at)gmail(dot)com> writes:
> Thanks for the suggestion. I used it in v4 of the patch.

I reviewed this and made some changes, some cosmetic some less so.

Notably, I was bemused that of the four calls of
pgstat_fetch_stat_local_beentry, three tested for a NULL result even
though they cannot get one, while the fourth (pg_stat_get_backend_idset)
*is* at hazard of a NULL result but lacked a check. I changed
pg_stat_get_backend_idset so that it too cannot get a NULL, and deleted
the dead code from the other callers.

A point that still bothers me a bit about pg_stat_get_backend_idset is
that it could miss or duplicate some backend IDs if the user calls
pg_stat_clear_snapshot() partway through the SRF's run, and we reload
a different set of backend entries than we had before. I added a comment
about that, with an argument why it's not worth working harder, but
is the argument convincing? If not, what should we do?

Also, I realized that the functions we're changing here are mostly
not exercised in the current regression tests :-(. So I added a
small test case.

I think this is probably committable if you agree with my changes.

regards, tom lane