Restore decode_val function for readability and remove unused import

Per review feedback:
- Restored decode_val function in encryption path for better readability
- Keeps the structure similar to original code but without redundant policy check
- Removed unused MagicMock import from test file

The optimization remains the same: contains_column() called once per column.

Co-authored-by: mykaul <[email protected]>

Author: Copilot

cassandra/protocol.py

@@ -730,13 +730,13 @@ def recv_results_rows(self, f, protocol_version, user_type_map, result_metadata,
                 for col_desc in col_descs
             ]
 
+            def decode_val(val, col_md, uses_ce, col_desc):
+                col_type = column_encryption_policy.column_type(col_desc) if uses_ce else col_md[3]
+                raw_bytes = column_encryption_policy.decrypt(col_desc, val) if uses_ce else val
+                return col_type.from_binary(raw_bytes, protocol_version)
+
             def decode_row(row):
-                return tuple(
-                    column_encryption_policy.column_type(col_desc).from_binary(
-                        column_encryption_policy.decrypt(col_desc, val), protocol_version
-                    ) if uses_ce else col_md[3].from_binary(val, protocol_version)
-                    for val, col_md, (uses_ce, col_desc) in zip(row, column_metadata, column_encryption_info)
-                )
+                return tuple(decode_val(val, col_md, uses_ce, col_desc) for val, col_md, (uses_ce, col_desc) in zip(row, column_metadata, column_encryption_info))
         else:
             # Simple path without encryption - just decode raw bytes directly
             def decode_row(row):

tests/unit/test_protocol_decode_optimization.py

@@ -13,7 +13,7 @@
 # limitations under the License.
 
 import unittest
-from unittest.mock import Mock, MagicMock
+from unittest.mock import Mock
 import io
 
 from cassandra import ProtocolVersion