diff --git a/README.md b/README.md
index e99b918..1eb367c 100644
--- a/README.md
+++ b/README.md
@@ -88,7 +88,9 @@ We test this foreign data wrapper on Ubuntu Server 18.04 using PostgreSQL-11 tog
 
 - The first attribute in the table definition must be the primary key.
 
-- Composite primary key is not supported for now.
+- Composite primary key can be achieved via creating a new data type `CREATE TYPE ... AS`.
+
+- Do not support secondary index.
 
 - ACID relies on the storage engine.