pg_user_mappings
   The view pg_user_mappings provides access
   to information about user mappings.  This is essentially a publicly
   readable view of
   pg_user_mapping
   that leaves out the options field if the user has no rights to use
   it.
  
Table 54.34. pg_user_mappings Columns
| Column Type Description | 
|---|
| 
        OID of the user mapping | 
| 
        The OID of the foreign server that contains this mapping | 
| 
        Name of the foreign server | 
| 
        OID of the local role being mapped, or zero if the user mapping is public | 
| 
        Name of the local user to be mapped | 
| 
        User mapping specific options, as “keyword=value” strings | 
   To protect password information stored as a user mapping option,
   the umoptions column will read as null
   unless one of the following applies:
   
      current user is the user being mapped, and owns the server or
      holds USAGE privilege on it
     
      current user is the server owner and mapping is for PUBLIC
     
current user is a superuser