System Catalogs Definitions - pg_user_mappings - 《Greenplum Database v6.23 Documentation》

The pg_user_mappings view provides access to information about user mappings. This view is essentially a public-readble view of the pg_user_mapping system catalog table that omits the options field if the user does not have access rights to view it.

column	type	references	description
`umid`	oid	pg_user_mapping.oid	OID of the user mapping.
`srvid`	oid	pg_foreign_server.oid	OID of the foreign server that contains this mapping.
`srvname`	text	pg_foreign_server.srvname	Name of the foreign server.
`umuser`	oid	pg_authid.oid	OID of the local role being mapped, 0 if the user mapping is public.
`usename`	name		Name of the local user to be mapped.
`umoptions`	text[]		User mapping-specific options, as “keyword=value” strings.

To protect password information stored as a user mapping option, the umoptions column reads as null unless one of the following applies:

The current user is the user being mapped, and owns the server or holds USAGE privilege on it.
The current user is the server owner and the mapping is for PUBLIC.
The current user is a superuser.

Parent topic: System Catalogs Definitions