[postgis-devel] Re: [postgis-users] create tables smarter

[Tom Lane]

Markus Schaber <schabi at logix-tt.com> writes:
> Is it possible for functions and operators to change the typmod?

In general the output of a function has no typmod (or equivalently
typmod -1).  The only exception that I can think of offhand is that
we know the special "length coercion" cast functions deliver results
that are constrained by the typmod supplied to them.

> We have the problem that e. G. scaling or translating does not change
> the typemod, while intersection will need to "broaden" the type of
> geometry, or force2d will change the dimensional part.

I don't see the problem really.  In general the system doesn't assume
that an operation on a datatype yields a value with any particular
typmod properties.

			regards, tom lane