Re: Distinct types

Simon Riggs <simon@2ndQuadrant.com> writes:
> On Fri, 2008-11-28 at 11:20 -0500, Tom Lane wrote:
>> If it's going to take a significant amount of work then I think someone
>> ought to provide an actual justification why it's worth the work.

> Few thoughts: 

> * Domains don't work very well in conjunction with arrays. 

But distinct types would somehow work better?

> * Strong typing is preferable in complex applications to avoid errors
> like sum(ordinal_column). Most developers use this all the time in their
> 3GL code but cannot use it in SQL.

The problem I see with distinct types is that the typing is *too*
strong --- the datatype has in fact got no usable operations whatever.

> * Allows migration of code easier from places that use strange sounding
> datatypes that can be mapped easily to existing datatypes.

Again, distinct types do *not* provide a "mapping to existing types",
because none of the operations carry along.  Domains would be more
nearly what you want for that.
        regards, tom lane