Re: Add Pipelining support in psql

On Mon, Apr 21, 2025 at 03:22:28PM +0900, Michael Paquier wrote:
> Anyway, I don't think that there is much we can do under a
> PGRES_FATAL_ERROR in this code path when discarding the pipe results.
> As far as I can tell, the server has failed the query suddenly and the
> whole pipeline flow is borked. The best thing that I can think of is
> to discard all the results while decrementing the counters, then let
> psql complain about that like in the attached. I've added two tests
> in TAP, as these trigger a FATAL in the backend so we cannot use the
> normal SQL route, so as we have some coverage.
>
> @Anthonin: Any thoughts or comments, perhaps? A second opinion would
> be welcome here.

While considering more ways to test this patch, I've recalled that
injection points that issue a FATAL in the backend to emulate the
original failure with more query patterns can provide more coverage,
and the discard cleanup is showing stable enough as presented in the
patch. I am wondering if we could not be smarter with the handling of
the counters, but I really doubt that there is much more we can do
under a PGRES_FATAL_ERROR.
--
Michael