Fixes #490: Ensure custom types support pickling.

Previously `NamedRowTuple` did not roundtrip successfully.
Added tests for all custom types.

tests/unit/test_types.py

@@ -0,0 +1,35 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pickle
+from datetime import datetime, time
+from decimal import Decimal
+
+from trino import types
+
+import pytest
+
+IDENTITY = lambda v: v
+
+type_instances = [
+    (types.Time(time(11, 47, 23), Decimal(0.314)), lambda v: v.to_python_type()),
+    (types.TimeWithTimeZone(time(11, 47, 23), Decimal(0.314)), lambda v: v.to_python_type()),
+    (types.Timestamp(datetime(2024, 10, 15, 11, 47, 23), Decimal(0.314)), lambda v: v.to_python_type()),
+    (types.TimestampWithTimeZone(datetime(2024, 10, 15, 11, 47, 23), Decimal(0.314)), lambda v: v.to_python_type()),
+    (types.NamedRowTuple(["Alice", 38], ["name", "age"], ["varchar", "integer"]), IDENTITY),
+]
+
+@pytest.mark.parametrize("value,fn", type_instances)
+def test_pickle_roundtripping(value, fn):
+    bytes = pickle.dumps(value)
+    unpickled_value = pickle.loads(bytes)
+    assert fn(value) == fn(unpickled_value)

trino/types.py

@@ -111,5 +111,14 @@ def __getattr__(self, name: str) -> Any:
         if self._names.count(name):
             raise ValueError("Ambiguous row field reference: " + name)
 
+    def __getnewargs__(self):
+        return (tuple(self), (), ())
+
+    def __getstate__(self):
+        return vars(self)
+
+    def __setstate__(self, state):
+        vars(self).update(state)
+
     def __repr__(self) -> str:
         return self._repr