Re: libpq and prepared statements progress for 8.0

There was some previous discussion of whether DBD:pg should continue
using libpq or implement the wire protocol in Perl, and whether ODBC
should move to using libpq.

I think we should favor libpq usage wherever possible and only
re-implement it in the native language when required, like for jdbc/java.
I think having all interfaces take advantage of libpq improvements and
features is a major win.  If we need to add things to libpq to make it
easier, fine, but that is minor work compared to maintaining separate
wire protocol for each interface language.

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Tom Lane wrote:
> Oliver Jowett <oliver@opencloud.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
> 
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