Re: Fix PL/Python metadata when there is no result

Peter Eisentraut <peter_e@gmx.net> writes:
> On lör, 2012-02-25 at 18:03 +0100, Jean-Baptiste Quenot wrote:
>> IMO raising an error is much better because:
>> 1) It is not a valid usecase to retrieve result metadata when no rows
>> are expected to be returned

> Which led me to think, how are you actually expected to know when no
> rows are expected to be returned, in PL/Python?  You can look at
> result.status(), which returns a numeric SPI status, but that seems
> fragile.  I notice that result.nrows() returns None when no rows are
> returned.  Is that good enough?  In that case, we should document that
> and then make the new functions throw exceptions like you suggest.

Wait a minute ... I don't understand why that's not a valid use-case.
I have seen more than one piece of code that does a SELECT ... LIMIT 0
or equivalent for the express purpose of finding out the rowtype
produced by a particular query.  Why would we make it impossible to do
that in pl/python?  Or are we talking about two different things?
        regards, tom lane