"Jonah H. Harris" <jonah.harris@gmail.com> writes:
> On 4/2/06, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> If you're expecting that you'll be able to write BYTEA(n) and avoid
>> storing a length word, you'll find that it's not a trivial matter.
> It may not be trivial, but it's certainly not impossible.
A word to the wise is sufficient: function result types don't have
known typmods, and for the most part expression results don't either.
Changing that is not "impossible", but the level of pain vastly exceeds
what this feature would be worth. And that's not even the only
problem.
If you're desperate to have something like this, you could create one
or more fixed-size datatypes (ie, with various positive typlen values).
But I don't see a practical way to use a typmod in determining the
physical width.
regards, tom lane