Re: Append with naive multiplexing of FDWs

On Mon, Aug 31, 2020 at 6:20 PM Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com> wrote:
> * I know your patch is a POC one, but one concern about it (and
> Horiguchi-san's patch set) is concurrent data fetches by multiple
> foreign scan nodes using the same connection in the case of
> postgres_fdw. Here is an example causing an error:

> select * from pt1, pt2 where pt2.a = 't22' or pt2.a = 't23';
> ERROR: another command is already in progress
> CONTEXT: remote SQL command: DECLARE c4 CURSOR FOR
> SELECT a, b FROM public.t22 WHERE (((a = 't22'::text) OR (a = 't23'::text)))

> (Horiguchi-san’s patch set doesn't work for this query either, causing
> the same error. Though, it looks like he intended to handle cases
> like this by a queuing system added to postgres_fdw to process such
> concurrent data fetches.)

I was wrong here; Horiguchi-san's patch set works well for this query.
Maybe I did something wrong when testing his patch set. Sorry for
that.

Best regards,
Etsuro Fujita