Re: libpq and prepared statements progress for 8.0

Oliver Jowett <oliver(at)opencloud(dot)com> writes:
> Tom reckons that PREPARE (at the SQL level) taking unknown types is not
> useful as there is no feedback mechanism along the lines of the V3
> protocol Describe messages to let the client find out what types were
> inferred by the PREPARE.

> I am saying this doesn't matter as the client can still use the
> resulting statement just fine without knowing the types. So allowing
> 'unknown' in PREPARE *is* useful.

Well, that was not quite my point, but I guess I wasn't clear. My
reasoning was more like this:
1. What we have now doesn't do what DBD::Pg needs.
2. We can fix it with some-small-amount-of-work in libpq (to add some API),
or with some-probably-also-small-amount-of-work in the backend (to
kluge up SQL PREPARE to allow "unknown").
3. The libpq-side solution is more generally useful, because it can support
feedback about the resolved datatypes.
4. Therefore, we should fix it in libpq.

Note that point 3 is not dependent on whether DBD::Pg in particular
needs this functionality --- somebody out there certainly will.

regards, tom lane