On 18.06.26 16:51, Robert Haas wrote:
The reason I somewhat hesitate to endorse that specific proposal is
that I'm not convinced that we should actually treat this as a form of
casting. Casts can be set to IMPLICIT or ASSIGNMENT or EXPLICIT, and
they can be WITHOUT FUNCTION or WITH INOUT, and none of that can be
relevant here. A CAST with FORMAT always needs to be implemented by a
function, is always explicit from a syntax point of view, and the code
to implement probably looks pretty different from the code needed for
a non-FORMAT cast. I am somewhat inclined to think we want something
that's like a cast function but actually a wholly separate mechanism,
e.g. a new pg_formatter catalog. I note that Jian He proposed putting
something in pg_type but I don't see how that can work, since there
are two types involved.
I don't accept the argument that we should start with this and extend
it later. The patch as proposed is just syntactic sugar. Said another
way, there is existing syntax that already delivers the functionality.
So I don't see why we would rush out support for a bit of new syntax;
anyone who wants to use this functionality can already do so. Getting
the infrastructure right is, IMHO, the interesting part of the
project, and I think that work needs to be done first.
I don't really understand the purpose of this feature to begin with.
You can already call the formatting functions directly. Does this cast
syntax offer anything on top of that?
