API tweaks for Redash use

Add arg to disable username / password check and add direct fetcharrow methods to make things easier to use.

Author: Niall Egan <niall.egan@databricks.com>

Author: Niall Egan

cmdexec/clients/python/src/databricks/sql/client.py

@@ -74,6 +74,8 @@ def __init__(self,
         #   Tag to add to User-Agent header. For use by partners.
         # _username, _password
         #   Username and password Basic authentication (no official support)
+        # _use_cert_as_auth
+        #  Use a TLS cert instead of a token or username / password (internal use only)
         # _enable_ssl
         #  Connect over HTTP instead of HTTPS
         # _port
@@ -100,8 +102,8 @@ def __init__(self,
             authorization_header = "Basic {}".format(auth_credentials_base64)
         elif access_token:
             authorization_header = "Bearer {}".format(access_token)
-        else:
-            raise ValueError("No valid authentication settings.")
+        elif not (kwargs.get("_use_cert_as_auth") and kwargs.get("_tls_client_cert_file")):
+            raise ValueError("No valid authentication settings. Please provide an access token.")
 
         if not kwargs.get("_user_agent_entry"):
             useragent_header = "{}/{}".format(USER_AGENT_NAME, __version__)
@@ -423,6 +425,20 @@ def fetchmany(self, n_rows: int) -> List[Tuple]:
         else:
             raise Error("There is no active result set")
 
+    def fetchall_arrow(self):
+        self._check_not_closed()
+        if self.active_result_set:
+            return self.active_result_set.fetchall_arrow()
+        else:
+            raise Error("There is no active result set")
+
+    def fetchmany_arrow(self, n_rows):
+        self._check_not_closed()
+        if self.active_result_set:
+            return self.active_result_set.fetchmany_arrow(n_rows)
+        else:
+            raise Error("There is no active result set")
+
     def cancel(self) -> None:
         """
         Cancel a running command.