Re:Re: Bypassing cursors in postgres_fdw to enable parallel plans

At 2026-06-29 17:27:17，"Rafia Sabih" <rafia(dot)pghackers(at)gmail(dot)com> wrote ：

>I understand your concern and I tried to solve it by passing fsstate now,
>also saving a backpointer to the node in active_fsstate to solve the issue
>with make_tuple_from_result_row. Since we need to have conn from fsstate, I
>am not sure how we can do that if we have only active_fsstate passed to the
>function.

I have reviewed all your previous patch revisions and tested the v12 patch.
You have fixed the issue raised by Robert where active_scan was not cleared when it ought to have been.
However, in my opinion, active_scan is cleared prematurely before the drain loop finishes executing.
If an error occurs mid-drain (such as query cancellation), the connection remains in an in-flight query state with no active_scan referencing it.
In the subsequent postgresEndForeignScan, is_active_scan() will return false, so pgfdw_cancel_scan() will never be invoked.
In subsequent queries, conn_state->active_scan may become a dangling pointer, triggering a crash.
I have written a test case that reproduces this crash to confirm the bug.

Best regards,

--

Yilin Zhang