Add support for sa.Time type by storing it as a STRING in ISO 8601 format

Author: florinutz

src/sqlalchemy_cratedb/compiler.py

@@ -246,6 +246,15 @@ def visit_datetime(self, type_, **kw):
     def visit_date(self, type_, **kw):
         return "TIMESTAMP"
 
+    def visit_time(self, type_, **kw):
+        """
+        CrateDB has no storable `TIME` column type. Plain `TIME` does not exist,
+        and `TIME WITH TIME ZONE` (TIMETZ) is literal/cast-only ("does not support
+        storage"). So store the time-of-day as a `STRING`, holding the value in
+        ISO 8601 format (e.g. ``19:00:30.123456``).
+        """
+        return "STRING"
+
     def visit_ARRAY(self, type_, **kw):
         if type_.dimensions is not None and type_.dimensions > 1:
             raise NotImplementedError("CrateDB doesn't support multidimensional arrays")

src/sqlalchemy_cratedb/dialect.py

@@ -21,7 +21,7 @@
 
 import logging
 import warnings
-from datetime import date, datetime
+from datetime import date, datetime, time
 
 from sqlalchemy import types as sqltypes
 from sqlalchemy.engine import default, reflection
@@ -167,10 +167,31 @@ def process(value):
         return process
 
 
+class Time(sqltypes.Time):
+    def bind_processor(self, dialect):
+        def process(value):
+            if value is not None:
+                return value.isoformat()
+            return None
+
+        return process
+
+    def result_processor(self, dialect, coltype):
+        def process(value):
+            if value is None:
+                return None
+            if isinstance(value, time):
+                return value
+            return time.fromisoformat(value)
+
+        return process
+
+
 colspecs = {
     sqltypes.Date: Date,
     sqltypes.DateTime: DateTime,
     sqltypes.TIMESTAMP: DateTime,
+    sqltypes.Time: Time,
 }
 
 if SA_VERSION >= SA_2_0:

tests/create_table_test.py

@@ -78,6 +78,30 @@ class User(self.Base):
             sa.util.immutabledict({}),
         )
 
+    def test_table_time_type(self):
+        """
+        `sa.Time` has no native CrateDB counterpart and is stored as `STRING`.
+
+        Validates the fix for https://github.com/crate/sqlalchemy-cratedb/issues/206,
+        where `sa.Time` previously compiled to `TIME`, which CrateDB rejects with
+        `SQLParseException[Cannot find data type: time]`.
+        """
+
+        class Schedule(self.Base):
+            __tablename__ = "schedule"
+            name = sa.Column(sa.String, primary_key=True)
+            time_col = sa.Column(sa.Time)
+
+        self.Base.metadata.create_all(bind=self.engine)
+        fake_cursor.execute.assert_called_with(
+            (
+                "\nCREATE TABLE schedule (\n\tname STRING NOT NULL, "
+                "\n\ttime_col STRING, "
+                "\n\tPRIMARY KEY (name)\n)\n\n"
+            ),
+            sa.util.immutabledict({}),
+        )
+
     def test_column_obj(self):
         class DummyTable(self.Base):
             __tablename__ = "dummy"

tests/datetime_test.py

@@ -105,6 +105,7 @@ class FooBar(Base):
     date = sa.Column(sa.Date)
     datetime_notz = sa.Column(DateTime(timezone=False))
     datetime_tz = sa.Column(DateTime(timezone=True))
+    time = sa.Column(sa.Time)
 
 
 @pytest.fixture
@@ -228,3 +229,33 @@ def test_datetime_date(session):
     # Compare outcome.
     assert result["datetime_notz"] == dt.datetime(2009, 5, 13, 0, 0, 0)
     assert result["datetime_tz"] == dt.datetime(2009, 5, 13, 0, 0, 0)
+
+
+@pytest.mark.skipif(SA_VERSION < SA_1_4, reason="Test case not supported on SQLAlchemy 1.3")
+def test_time(session):
+    """
+    An integration test for `sa.Time`.
+
+    CrateDB has no native `TIME` type, so the dialect stores it as a `STRING`
+    in ISO 8601 format and parses it back into a `dt.time` object on read.
+
+    Validates the fix for https://github.com/crate/sqlalchemy-cratedb/issues/206.
+    """
+
+    # insert
+    foo_item = FooBar(
+        name="foo",
+        time=dt.time(19, 0, 30, 123456),
+    )
+    session.add(foo_item)
+    session.commit()
+    session.execute(sa.text("REFRESH TABLE foobar"))
+
+    # query
+    result = (
+        session.execute(sa.select(FooBar.name, FooBar.time)).mappings().first()
+    )
+
+    # compare
+    assert result["time"] == dt.time(19, 0, 30, 123456)
+    assert isinstance(result["time"], dt.time)