Set datetime, date, time and timestamp columns to Nullable to avoid N…

…ULL cast to epoch (#142)

* Fix lint

* Fix lint

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "shaped-target-clickhouse"
-version = "0.2.3"
+version = "0.2.4"
 description = "`target-clickhouse` is a Singer target for clickhouse, built with the Meltano Singer SDK."
 readme = "README.md"
 authors = ["Ben Theunissen"]

target_clickhouse/connectors.py

@@ -100,6 +100,14 @@ def to_sql_type(self, jsonschema_type: dict) -> sqlalchemy.types.TypeEngine:
             sql_type = typing.cast(
                 sqlalchemy.types.TypeEngine, clickhouse_sqlalchemy_types.Int64(),
             )
+        # All date and time types should be flagged as Nullable to allow for NULL value.
+        elif type(sql_type) in [
+            sqlalchemy.types.DATE,
+            sqlalchemy.types.TIMESTAMP,
+            sqlalchemy.types.TIME,
+            sqlalchemy.types.DATETIME,
+        ]:
+            sql_type = clickhouse_sqlalchemy_types.Nullable(sql_type)
 
         return sql_type
 

tests/target_test_cases.py

@@ -10,7 +10,7 @@
 logger = logging.getLogger(__name__)
 
 class TestDateTypeTargetClickhouse(TargetClickhouseFileTestTemplate):
-    """Test date type can be ingested into Clickhouse."""
+    """Test date type, and null date type can be ingested into Clickhouse."""
 
     name = "date_type"
 
@@ -30,6 +30,11 @@ def validate(self) -> None:
             record for record in result if record[0] == record_id_2
         ]))
         assert record_2[1] == datetime.date(2024, 3, 16)
+        record_id_3 = 3
+        record_3 = next(iter([
+            record for record in result if record[0] == record_id_3
+        ]))
+        assert record_3[1] is None
 
 custom_target_test_suite = TestSuite(
     kind="target",