The system catalog table pg_extension stores information about installed extensions.

    column type references description
    extname name Name of the extension.
    extowner oid pg_authid.oid Owner of the extension
    extnamespace oid pg_namespace.oid Schema containing the extension exported objects.
    extrelocatable boolean True if the extension can be relocated to another schema.
    extversion text Version name for the extension.
    extconfig oid[] pg_class.oid Array of regclass OIDs for the extension configuration tables, or NULL if none.
    extcondition text[] Array of WHERE-clause filter conditions for the extension configuration tables, or NULL if none.

    Unlike most catalogs with a namespace column, extnamespace does not imply that the extension belongs to that schema. Extension names are never schema-qualified. The extnamespace schema indicates the schema that contains most or all of the extension objects. If extrelocatable is true, then this schema must contain all schema-qualifiable objects that belong to the extension.

    Parent topic: System Catalogs Definitions