Re: Avoiding rewrite in ALTER TABLE ALTER TYPE

On Fri, Dec 31, 2010 at 12:34:50AM -0500, Robert Haas wrote:
> On Thu, Dec 30, 2010 at 8:35 PM, Noah Misch <noah@leadboat.com> wrote:
> > 4. A FuncExpr node has answers given by the bitwise-AND of its funcexempt field
> > and the answers from its first argument.
> 
> Why its first argument?

funcexempt would only be nonzero for FuncExpr of length coercion casts.  Those
have the subject datum as a first argument, typmod as second, and is-explicit
boolean as third.  The other arguments are effectively already validated.

That brings up a point -- the exemptor function also needs an is-explicit
argument, as that affects the decision for some types.