cql3: Implement use_statement::execute()

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

cql3/statements/use_statement.hh

@@ -62,11 +62,9 @@ public:
 
     virtual future<::shared_ptr<transport::messages::result_message>>
     execute(service::storage_proxy& proxy, service::query_state& state, const query_options& options) override {
-        throw std::runtime_error("not implemented");
-#if 0
-        state.getClientState().setKeyspace(keyspace);
-        return new ResultMessage.SetKeyspace(keyspace);
-#endif
+        state.get_client_state().set_keyspace(_keyspace);
+        auto result =::make_shared<transport::messages::result_message::set_keyspace>(_keyspace);
+        return make_ready_future<::shared_ptr<transport::messages::result_message>>(result);
     }
 
     virtual future<::shared_ptr<transport::messages::result_message>>

transport/messages/result_message.hh

@@ -7,14 +7,25 @@ namespace messages {
 
 // FIXME: stub
 class result_message {
+public:
     virtual ~result_message() {}
 
     class void_message;
+    class set_keyspace;
 };
 
 class result_message::void_message : public result_message {
 };
 
+class result_message::set_keyspace : public result_message {
+private:
+    sstring _keyspace;
+public:
+    set_keyspace(const sstring& keyspace)
+        : _keyspace{keyspace}
+    { }
+};
+
 }
 
 }