Re: Typmod associated with multi-row VALUES constructs

On Wed, Dec 7, 2016 at 1:03 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

> Still, things have been like this since 8.2 when we implemented multi-row
> VALUES, and nobody's noticed up to now.  Maybe the right answer is to
> change the data structure in HEAD and decree that we won't fix it in back
> branches.  I don't really like that answer though ...
>

​The merit of "won't back-patch"​ is that at least you don't punish those
who are being lazy (in a good sense) but generating values in subsequent
lines that conform to the type specification of the first record.  We
already implicitly accept such behavior elsewhere - though probably with
better validation - so keeping it here is defense-able.  We dislike
changing query plans in back branches and this really isn't that different.

The concern, especially since this can propagate to a CREATE TABLE AS, is
whether there is some kind of fundamental storage risk being introduced
that we do not want to have happen no matter how rare.  /me feels deja-vu...

David J.