Historical version. PostgreSQL 9.2 has reached end of support. 2017-11-09. See the current manual.
45.56. pg_group
The view pg_group exists for backwards compatibility: it emulates a catalog that existed in PostgreSQL before version 8.1. It shows the names and members of all roles that are marked as not rolcanlogin, which is an approximation to the set of roles that are being used as groups.
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