Re: [EXTERNAL] Re: Add non-blocking version of PQcancel

On Tue, 12 Mar 2024 at 10:19, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> If we do this and we see conn.status is not ALLOCATED, meaning a cancel
> is already ongoing, shouldn't we leave conn.status alone instead of
> changing to CONNECTION_BAD? I mean, we shouldn't be juggling the elbow
> of whoever's doing that, should we? Maybe just add the error message
> and return 0?

I'd rather fail as hard as possible when someone is using the API
wrongly. Not doing so is bound to cause confusion imho. e.g. if the
state is still CONNECTION_OK because the user forgot to call
PQcancelReset then keeping the connection status "as is" might seem as
if the cancel request succeeded even though nothing happened. So if
the user uses the API incorrectly then I'd rather use all the avenues
possible to indicate that there was an error. Especially since in all
other cases if PQcancelStart returns false CONNECTION_BAD is the
status, and this in turn means that PQconnectPoll will return
PGRES_POLLING_FAILED. So I doubt people will always check the actual
return value of the function to check if an error happened. They might
check PQcancelStatus or PQconnectPoll instead, because that integrates
easier with the rest of their code.