Why does DISABLE PRIMARY KEY CASCADE doesn't set Unique Index unusable?

Question

can anyone explain to me why the execution of "DISABLE PRIMARY KEY CASCADE" on a PK doesn't set the corresponding unique (!) index to unusable?

As far as I know the CASCADE option should do exactly that... However, I observed differently on several occasions.

Hope some of you can help.

best regards, daZza

Answer 1

The cascade option disables constraints that are dependent on this one, such as foreign keys dependent on a primary or unique constraint.

A unique index is not a constraint, although it acts as one.

In general I would advise that you create non-unique indexes to support a primary or unique key, not a unique index, for precisely this reason, and to allow constraints to be deferrable, or entirely dropped and recreated without having to recreate the index.