Re: Using PQexecQuery in pipeline mode produces unexpected Close messages

On 2022-Jun-10, Kyotaro Horiguchi wrote:

> (Moved to -hackers)
> 
> At Wed, 8 Jun 2022 17:08:47 +0200, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote in 
> > What that Close message is doing is closing the unnamed portal, which
> > is otherwise closed implicitly when the next one is opened.  That's how
> > single-query mode works: if you run a single portal, it'll be kept open.
> > 
> > I believe that the right fix is to not send that Close message in
> > PQsendQuery.
> 
> Agreed. At least Close message in that context is useless and
> PQsendQueryGuts doesn't send it. And removes the Close message surely
> fixes the issue.

So, git archaeology led me to this thread
https://postgr.es/m/202106072107.d4i55hdscxqj@alvherre.pgsql
which is why we added that message in the first place.

I was about to push the attached patch (a merged version of Kyotaro's
and mine), but now I'm wondering if that's the right approach.

Alternatives:

- Have the client not complain if it gets CloseComplete in idle state.
  (After all, it's a pretty useless message, since we already do nothing
  with it if we get it in BUSY state.)

- Have the server not send CloseComplete at all in the cases where
  the client is not expecting it.  Not sure how this would be
  implemented.

- Other ideas?

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/
"That sort of implies that there are Emacs keystrokes which aren't obscure.
I've been using it daily for 2 years now and have yet to discover any key
sequence which makes any sense."                        (Paul Thomas)