pg_extension

The system catalog table pg_extension stores information about installed extensions.

Table 1. pg_catalog.pg_exttable

column	type	references	description
oid	oid		The object ID
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.