Robert Haas <robertmhaas@gmail.com> writes:
> On Thu, Dec 10, 2009 at 11:54 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> The problem with USING is that it is not merely a join condition but
>> affects the set of columns emitted by the join. It can't be converted
>> to a simple ON without changing the semantics, and I don't believe we
>> should try.
> The OP seemed to be pretty clear on what the semantics should be, and
> I'm not confused either. Why are you? :-)
I'm not confused: it's an error condition. You have not explained why
it isn't.
What would actually be ideal is to throw an error on the attempted column
rename, but I doubt the problem is worth the additions to system
infrastructure that would be necessary to make that happen.
regards, tom lane