The catalog pg_opfamily defines operator families. Each operator family is a collection of operators and associated support routines that implement the semantics specified for a particular index access method. Furthermore, the operators in a family are all «compatible», in a way that is specified by the access method. The operator family concept allows cross-data-type operators to be used with indexes and to be reasoned about using knowledge of access method semantics.
Operator families are described at length in Sezione 35.14, «Interfacing Extensions To Indexes».
Tabella 45.29. pg_opfamily Columns