pg_extension
   The catalog pg_extension stores information
   about the installed extensions.  See Section 38.17
   for details about extensions.
  
Table 52.22. pg_extension Columns
Column Type Description  | 
|---|
        Row identifier  | 
        Name of the extension  | 
        Owner of the extension  | 
        Schema containing the extension's exported objects  | 
        True if extension can be relocated to another schema  | 
        Version name for the extension  | 
        
       Array of   | 
        
       Array of   | 
   Note that unlike most catalogs with a “namespace” column,
   extnamespace is not meant to imply
   that the extension belongs to that schema.  Extension names are never
   schema-qualified.  Rather, extnamespace
   indicates the schema that contains most or all of the extension's
   objects.  If extrelocatable is true, then
   this schema must in fact contain all schema-qualifiable objects
   belonging to the extension.