Re: BUG #17355: Server crashes on ExecReScanForeignScan in postgres_fdw when accessing foreign partition

Hi Alexander,

On Tue, Jan 25, 2022 at 3:00 AM Alexander Lakhin <exclusion@gmail.com> wrote:
> I've made a simple isolation test (see attachment) to confirm this. And
> it crashes without the fix as you said.
> With your fix it works as expected

Thanks for testing!

> (I was wondering how "plan->operation
> != CMD_SELECT" with RETURNING will work and I haven't seen any issues yet.)

EvalPlanQual rechecking is irrelevant for direct modifications even
when the UPDATE/DELETE query has a RETURNING clause; in which case we
compute the RETURNING expressions locally, but that is done *after*
updating/deleting foreign rows on the remote side.

> (Besides that I've observed an infinite waiting for ShareLock with
> step "s1i" { INSERT INTO pt VALUES (2000); }
> This doesn't happen with a regular (not foreign) table.)

You mean the lock wait occurs on the remote side, not on the local
side?  If so, I think that that is expected behavior because a write
conflict occurs on the remote side in that case.  Maybe I don’t fully
understand your words, so could you elaborate a bit more on your
observation?

Best regards,
Etsuro Fujita