Suppose I have a system where I have metadata such as:
table:
======
key
name
address
...
Then suppose I have a user-defined type described as so:
datasource
datasource-key
A) are there systems where it's possible to have keys based on user-defined types?
B) if so, how do you decompose the keys into a form suitable for querying?
C) is this a case where I'm just better off with a composite primary key?