Now that I've started to read this patch ... exactly what is the
argument for allowing a "mixed" notation (some of the parameters named
and some not)? ISTM that just serves to complicate both the patch
and the user's-eye view, for no real benefit.
Considering that we are worried about someday having to adjust to a
SQL standard in this area, I think we ought to be as conservative as
possible about what we introduce as user-visible features here.
As an example, if they do go with "=>" as the parameter marker,
mixed notation would become a seriously bad idea because it would be
impossible to distinguish incidental use of => as an operator from
mixed notation.
regards, tom lane