The catalog pg_auth_members shows the membership relations between roles. Any non-circular set of relationships is allowed.
Because user identities are cluster-wide, pg_auth_members is shared across all databases of a cluster: there is only one copy of pg_auth_members per cluster, not one per database.
Table 42-9. pg_auth_members Columns
|roleid||oid||pg_authid.oid||ID of a role that has a member|
|member||oid||pg_authid.oid||ID of a role that is a member of roleid|
|grantor||oid||pg_authid.oid||ID of the role that granted this membership|
|admin_option||bool||True if member may grant membership in roleid to others|