Using UUID as primary key

You can use whatever you want, just remember about some caveats, like issue with bitslice/bitmap indexes, which requires numerical ID

I would recommend using just a Unique Index for the UUID field and use it, it should cover most of the needs.

Personally I'd rather use a default numeric ID and if needed an additional UUID/GUID unique property.

To implement what you asked you can use something like:

Class My.TestClass Extends %Persistent
{
Property PrimaryUUID As %String [ InitialExpression = {$system.Util.CreateGUID()} ];
Property MyOtherData As %String;

Index PrimaryUUIDIndex On PrimaryUUID [ IdKey, Unique ];
}

In this way the primary key (PrimaryUUID) is automatically assigned, no need to set it manually, in SQL is mapped as ID (as well as PrimaryUUID).

Enrico