pg_extension
   The catalog pg_extension stores information
   about the installed extensions.  See Section 37.17
   for details about extensions.
  
Table 51.22. pg_extension Columns
| Name | Type | References | Description | 
|---|---|---|---|
| oid | oid | Row identifier | |
| extname | name | Name of the extension | |
| extowner | oid |  | Owner of the extension | 
| extnamespace | oid |  | Schema containing the extension's exported objects | 
| extrelocatable | bool | True if extension can be relocated to another schema | |
| extversion | text | Version name for the extension | |
| extconfig | oid[] |  | Array of regclassOIDs for the extension's configuration
       table(s), orNULLif none | 
| extcondition | text[] | Array of WHERE-clause filter conditions for the
       extension's configuration table(s), orNULLif none | 
   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.