pg_user_mapping stores the mappings from local user to remote. Access to this catalog is restricted from normal users, use the view pg_user_mappings instead.
|Row identifier (hidden attribute; must be explicitly selected)|
|OID of the local role being mapped, 0 if the user mapping is public|
|The OID of the foreign server that contains this mapping|
|User mapping specific options, as “keyword=value” strings|