Merge pull request piccolo-orm#60 from piccolo-orm/is_null

added is_null / is_not_null

Author: dantownsend

CHANGES

@@ -6,7 +6,6 @@ Changes
  * Added ``WhereRaw``, so raw SQL can be used in where clauses.
  * ``piccolo shell run`` now uses syntax highlighting - courtesy of Fingel.
 
-
 0.16.2
 ------
 Reordering the dependencies in requirements.txt when using ``piccolo asgi new``

docs/src/piccolo/query_clauses/where.rst

@@ -103,6 +103,44 @@ is_in / not_in
 
 -------------------------------------------------------------------------------
 
+is_null / is_not_null
+---------------------
+
+These queries work, but some linters will complain about doing a comparison
+with None:
+
+.. code-block:: python
+
+    b = Band
+
+    # Fetch all bands with a manager
+    b.select().where(
+        b.manager != None
+    ).run_sync()
+
+    # Fetch all bands without a manager
+    b.select().where(
+        b.manager == None
+    ).run_sync()
+
+To avoid the linter errors, you can use `is_null` and `is_not_null` instead.
+
+.. code-block:: python
+
+    b = Band
+
+    # Fetch all bands with a manager
+    b.select().where(
+        b.manager.is_not_null()
+    ).run_sync()
+
+    # Fetch all bands without a manager
+    b.select().where(
+        b.manager.is_null()
+    ).run_sync()
+
+-------------------------------------------------------------------------------
+
 Complex queries - and / or
 ---------------------------
 

piccolo/columns/base.py

@@ -15,6 +15,7 @@
     GreaterThan,
     ILike,
     In,
+    IsNotNull,
     IsNull,
     LessEqualThan,
     LessThan,
@@ -366,11 +367,28 @@ def __eq__(self, value) -> Where:  # type: ignore
             return Where(column=self, value=value, operator=Equal)
 
     def __ne__(self, value) -> Where:  # type: ignore
-        return Where(column=self, value=value, operator=NotEqual)
+        if value is None:
+            return Where(column=self, operator=IsNotNull)
+        else:
+            return Where(column=self, value=value, operator=NotEqual)
 
     def __hash__(self):
         return hash(self._meta.name)
 
+    def is_null(self) -> Where:
+        """
+        Can be used instead of `MyTable.column != None`, because some linters
+        don't like a comparison to None.
+        """
+        return Where(column=self, operator=IsNull)
+
+    def is_not_null(self) -> Where:
+        """
+        Can be used instead of `MyTable.column == None`, because some linters
+        don't like a comparison to None.
+        """
+        return Where(column=self, operator=IsNotNull)
+
     def as_alias(self, name: str) -> Column:
         """
         Allows column names to be changed in the result of a select.

piccolo/columns/operators/comparison.py

@@ -9,6 +9,10 @@ class IsNull(ComparisonOperator):
     template = "{name} IS NULL"
 
 
+class IsNotNull(ComparisonOperator):
+    template = "{name} IS NOT NULL"
+
+
 class Equal(ComparisonOperator):
     template = "{name} = {value}"
 

tests/apps/migrations/commands/test_base.py

@@ -12,7 +12,9 @@
 
 class TestBaseMigrationManager(TestCase):
     def test_create_migration_table(self):
-        self.assertTrue(BaseMigrationManager().create_migration_table())
+        self.assertTrue(
+            run_sync(BaseMigrationManager().create_migration_table())
+        )
 
     def tearDown(self):
         Migration.raw("DROP TABLE IF EXISTS migration").run_sync()

tests/table/test_select.py

@@ -77,6 +77,41 @@ def test_where_greater_than(self):
 
         self.assertEqual(response, [{"name": "Rustaceans"}])
 
+    def test_where_is_null(self):
+        self.insert_rows()
+
+        Band(name="Managerless", popularity=0, manager=None).save().run_sync()
+
+        queries = (
+            Band.select(Band.name).where(Band.manager == None),  # noqa
+            Band.select(Band.name).where(Band.manager.is_null()),
+        )
+
+        for query in queries:
+            response = query.run_sync()
+            self.assertEqual(response, [{"name": "Managerless"}])
+
+    def test_where_is_not_null(self):
+        self.insert_rows()
+
+        Band(name="Managerless", popularity=0, manager=None).save().run_sync()
+
+        queries = (
+            Band.select(Band.name).where(Band.manager != None),  # noqa
+            Band.select(Band.name).where(Band.manager.is_not_null()),
+        )
+
+        for query in queries:
+            response = query.run_sync()
+            self.assertEqual(
+                response,
+                [
+                    {"name": "Pythonistas"},
+                    {"name": "Rustaceans"},
+                    {"name": "CSharps"},
+                ],
+            )
+
     def test_where_greater_equal_than(self):
         self.insert_rows()