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db4o

db4o - unique constraints on a group of fields

I would like to have unique constraints operate on more than 1 field for several entities. How can I achieve this with db4o?

Thanks,

Walter

Solution

  • Currently db4o doesn't support the UniqueConstrain on multiple fields. You can set unique-constrains only field by field, but not combine them.

    @Ladlestein Well the intention is good, but it doesn't work. db4o manageds objects by it referencial identity. When you apply the unique-constrain on the Foo.name, you ensure that the reference is unique. So no other object can have the same reference to a name object. But you're not interested that the reference is unique, but you want to have a unique content of the names.