Primary Key from multiple attribute

[kryzhikh]

Hello,

Is there any way to have multiple attributes as a primary key? I have an object that has 2 string attributes and combination of them determines the object uniqueness.

Thanks.

[dimazen]

Hello, @kryzhikh! Unfortunately no. I was trying to manage stuff like that in the past but wasn't able to manage correct prefetch. Issue is in the predicate, when we have to fetch objects that has received IDs.
When key is one, then predicate is PK IN arrayOfPKs, however for multiple PKs it is hard to describe it. This should be either a very long (PK1 == A && PK2 == B) || (PK1 == A1 && PK2 == B) .... or something different. Do you have any idea, by the way?

[kryzhikh]

Thanks for the quick reply! No ideas so far.. I'll let you know, if I work it out.

[dimazen]

Well, we can go with PK1 IN firstPKArray AND PK2 IN secondPKArray. I assume, that sql does optimisation, so lookup don't have to be O(n^2). This might be an idea.