Creating a Unique Secondary Index as a Composite of a Row‑Level Security Constraint Column and a NUPI Column Set
You can create a USI for a row‑level security‑protected table as a composite of a row‑level security constraint column and the columns of a NUPI for the table. This property can be used to implement polyinstantiation.
Polyinstantiation is a property that allows a relation to contain multiple rows with the same primary key value, where the multiple instances are distinguished by their security levels, where a security level is defined by a row‑level security constraint column.
For this property not to violate the relational model, the security level instances would need to be defined as components of a composite primary key.