feat: Added support for check constraint (#679)

* feat: Added support for check constraint

* fix: change decimal out of scale ProgramingError to ValueError

* fix: skip check_constraints tests when running on emmulator

* fix: remove check constraint for emulator

django_spanner/__init__.py

@@ -5,6 +5,7 @@
 # https://developers.google.com/open-source/licenses/bsd
 
 import datetime
+import os
 
 # Monkey-patch AutoField to generate a random value since Cloud Spanner can't
 # do that.
@@ -24,6 +25,8 @@
 
 __version__ = pkg_resources.get_distribution("django-google-spanner").version
 
+USE_EMULATOR = os.getenv("SPANNER_EMULATOR_HOST") is not None
+
 check_django_compatability()
 register_expressions()
 register_functions()

django_spanner/features.py

@@ -184,7 +184,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "db_functions.comparison.test_cast.CastTests.test_cast_to_decimal_field",
         "model_fields.test_decimalfield.DecimalFieldTests.test_fetch_from_db_without_float_rounding",
         "model_fields.test_decimalfield.DecimalFieldTests.test_roundtrip_with_trailing_zeros",
-        # No CHECK constraints in Spanner.
+        # Spanner does not support unsigned integer field.
         "model_fields.test_integerfield.PositiveIntegerFieldTests.test_negative_values",
         # Spanner doesn't support the variance the standard deviation database
         # functions:

django_spanner/schema.py

@@ -7,6 +7,7 @@
 from django.db import NotSupportedError
 from django.db.backends.base.schema import BaseDatabaseSchemaEditor
 from django_spanner._opentelemetry_tracing import trace_call
+from django_spanner import USE_EMULATOR
 
 
 class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
@@ -472,8 +473,13 @@ def _alter_column_type_sql(self, model, old_field, new_field, new_type):
         )
 
     def _check_sql(self, name, check):
-        # Spanner doesn't support CHECK constraints.
-        return None
+        # Emulator does not support check constraints yet.
+        if USE_EMULATOR:
+            return None
+        return self.sql_constraint % {
+            "name": self.quote_name(name),
+            "constraint": self.sql_check_constraint % {"check": check},
+        }
 
     def _unique_sql(self, model, fields, name, condition=None):
         # Inline constraints aren't supported, so create the index separately.

noxfile.py

@@ -43,7 +43,7 @@ def lint(session):
     session.run("flake8", "django_spanner", "tests")
 
 
-@nox.session(python="3.6")
+@nox.session(python=DEFAULT_PYTHON_VERSION)
 def blacken(session):
     """Run black.
 

tests/system/django_spanner/models.py

@@ -21,3 +21,16 @@ class Number(models.Model):
 
     def __str__(self):
         return str(self.num)
+
+
+class Event(models.Model):
+    start_date = models.DateTimeField()
+    end_date = models.DateTimeField()
+
+    class Meta:
+        constraints = [
+            models.CheckConstraint(
+                check=models.Q(end_date__gt=models.F("start_date")),
+                name="check_start_date",
+            ),
+        ]

tests/system/django_spanner/test_check_constraint.py

@@ -0,0 +1,64 @@
+# Copyright 2021 Google LLC
+#
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file or at
+# https://developers.google.com/open-source/licenses/bsd
+
+from .models import Event
+from django.test import TransactionTestCase
+import datetime
+import unittest
+from django.utils import timezone
+from google.api_core.exceptions import OutOfRange
+from django.db import connection
+from django_spanner import USE_EMULATOR
+from tests.system.django_spanner.utils import (
+    setup_instance,
+    teardown_instance,
+    setup_database,
+    teardown_database,
+)
+
+
+@unittest.skipIf(
+    USE_EMULATOR, "Check Constraint is not implemented in emulator."
+)
+class TestCheckConstraint(TransactionTestCase):
+    @classmethod
+    def setUpClass(cls):
+        setup_instance()
+        setup_database()
+        with connection.schema_editor() as editor:
+            # Create the table
+            editor.create_model(Event)
+
+    @classmethod
+    def tearDownClass(cls):
+        with connection.schema_editor() as editor:
+            # delete the table
+            editor.delete_model(Event)
+        teardown_database()
+        teardown_instance()
+
+    def test_insert_valid_value(self):
+        """
+        Tests model object creation with Event model.
+        """
+        now = timezone.now()
+        now_plus_10 = now + datetime.timedelta(minutes=10)
+        event_valid = Event(start_date=now, end_date=now_plus_10)
+        event_valid.save()
+        qs1 = Event.objects.filter().values("start_date")
+        self.assertEqual(qs1[0]["start_date"], now)
+        # Delete data from Event table.
+        Event.objects.all().delete()
+
+    def test_insert_invalid_value(self):
+        """
+        Tests model object creation with invalid data in Event model.
+        """
+        now = timezone.now()
+        now_minus_1_day = now - timezone.timedelta(days=1)
+        event_invalid = Event(start_date=now, end_date=now_minus_1_day)
+        with self.assertRaises(OutOfRange):
+            event_invalid.save()

tests/system/django_spanner/test_decimal.py

@@ -6,14 +6,13 @@
 
 from .models import Author, Number
 from django.test import TransactionTestCase
-from django.db import connection, ProgrammingError
+from django.db import connection
 from decimal import Decimal
 from tests.system.django_spanner.utils import (
     setup_instance,
     teardown_instance,
     setup_database,
     teardown_database,
-    USE_EMULATOR,
 )
 
 
@@ -87,12 +86,8 @@ def test_decimal_precision_limit(self):
         Tests decimal object precission limit.
         """
         num_val = Number(num=Decimal(1) / Decimal(3))
-        if USE_EMULATOR:
-            with self.assertRaises(ValueError):
-                num_val.save()
-        else:
-            with self.assertRaises(ProgrammingError):
-                num_val.save()
+        with self.assertRaises(ValueError):
+            num_val.save()
 
     def test_decimal_update(self):
         """

tests/system/django_spanner/utils.py

@@ -15,11 +15,12 @@
 from test_utils.retry import RetryErrors
 
 from django_spanner.creation import DatabaseCreation
+from django_spanner import USE_EMULATOR
 
 CREATE_INSTANCE = (
     os.getenv("GOOGLE_CLOUD_TESTS_CREATE_SPANNER_INSTANCE") is not None
 )
-USE_EMULATOR = os.getenv("SPANNER_EMULATOR_HOST") is not None
+
 SPANNER_OPERATION_TIMEOUT_IN_SECONDS = int(
     os.getenv("SPANNER_OPERATION_TIMEOUT_IN_SECONDS", 60)
 )