pg_user_mapping #
   The catalog 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.
  
Table 51.66. pg_user_mapping Columns
| Column Type Description | 
|---|
| 
        Row identifier | 
| 
        OID of the local role being mapped, or zero if the user mapping is public | 
| 
        The OID of the foreign server that contains this mapping | 
| 
        User mapping specific options, as “keyword=value” strings |