Raise error on trying to create unique constraints with unsupported conditions

sql_server/pyodbc/schema.py

@@ -14,8 +14,9 @@
     Statement as DjStatement,
     Table,
 )
-from django.db.models import Index
+from django.db.models import Index, UniqueConstraint
 from django.db.models.fields import AutoField, BigAutoField
+from django.db.models.sql.where import AND
 from django.db.transaction import TransactionManagementError
 from django.utils.encoding import force_str
 
@@ -970,3 +971,9 @@ def remove_field(self, model, field):
         for sql in list(self.deferred_sql):
             if isinstance(sql, Statement) and sql.references_column(model._meta.db_table, field.column):
                 self.deferred_sql.remove(sql)
+
+    def add_constraint(self, model, constraint):
+        if isinstance(constraint, UniqueConstraint) and constraint.condition and constraint.condition.connector != AND:
+            raise NotImplementedError("The backend does not support %s conditions on unique constraint %s." %
+                                      (constraint.condition.connector, constraint.name))
+        super().add_constraint(model, constraint)

testapp/migrations/0008_test_unique_constraints.py

@@ -0,0 +1,68 @@
+# Generated by Django 3.1.5 on 2021-01-18 00:05
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('testapp', '0007_test_remove_onetoone_field_part2'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='TestUnsupportableUniqueConstraint',
+            fields=[
+                (
+                    'id',
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name='ID',
+                    ),
+                ),
+                ('_type', models.CharField(max_length=50)),
+                ('status', models.CharField(max_length=50)),
+            ],
+            options={
+                'managed': False,
+            },
+        ),
+        migrations.CreateModel(
+            name='TestSupportableUniqueConstraint',
+            fields=[
+                (
+                    'id',
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name='ID',
+                    ),
+                ),
+                ('_type', models.CharField(max_length=50)),
+                ('status', models.CharField(max_length=50)),
+            ],
+        ),
+        migrations.AddConstraint(
+            model_name='testsupportableuniqueconstraint',
+            constraint=models.UniqueConstraint(
+                condition=models.Q(
+                    ('status', 'in_progress'),
+                    ('status', 'needs_changes'),
+                    ('status', 'published'),
+                ),
+                fields=('_type',),
+                name='and_constraint',
+            ),
+        ),
+        migrations.AddConstraint(
+            model_name='testsupportableuniqueconstraint',
+            constraint=models.UniqueConstraint(
+                condition=models.Q(status__in=['in_progress', 'needs_changes']),
+                fields=('_type',),
+                name='in_constraint',
+            ),
+        ),
+    ]

testapp/models.py

@@ -1,6 +1,7 @@
 import uuid
 
 from django.db import models
+from django.db.models import Q
 from django.utils import timezone
 
 
@@ -71,3 +72,39 @@ class TestRemoveOneToOneFieldModel(models.Model):
     # thats already is removed.
     # b = models.OneToOneField('self', on_delete=models.SET_NULL, null=True)
     a = models.CharField(max_length=50)
+
+
+class TestUnsupportableUniqueConstraint(models.Model):
+    class Meta:
+        managed = False
+        constraints = [
+            models.UniqueConstraint(
+                name='or_constraint',
+                fields=['_type'],
+                condition=(Q(status='in_progress') | Q(status='needs_changes')),
+            ),
+        ]
+
+    _type = models.CharField(max_length=50)
+    status = models.CharField(max_length=50)
+
+
+class TestSupportableUniqueConstraint(models.Model):
+    class Meta:
+        constraints = [
+            models.UniqueConstraint(
+                name='and_constraint',
+                fields=['_type'],
+                condition=(
+                    Q(status='in_progress') & Q(status='needs_changes') & Q(status='published')
+                ),
+            ),
+            models.UniqueConstraint(
+                name='in_constraint',
+                fields=['_type'],
+                condition=(Q(status__in=['in_progress', 'needs_changes'])),
+            ),
+        ]
+
+    _type = models.CharField(max_length=50)
+    status = models.CharField(max_length=50)

testapp/tests/test_constraints.py

@@ -1,9 +1,14 @@
-from django.db.utils import IntegrityError
-from django.test import TestCase, skipUnlessDBFeature
+from django.db import IntegrityError, connections, migrations, models
+from django.db.migrations.state import ProjectState
+from django.test import TestCase, TransactionTestCase, skipUnlessDBFeature
 
+from sql_server.pyodbc.base import DatabaseWrapper
 from ..models import (
-    Author, Editor, Post,
-    TestUniqueNullableModel, TestNullableUniqueTogetherModel,
+    Author,
+    Editor,
+    Post,
+    TestUniqueNullableModel,
+    TestNullableUniqueTogetherModel,
 )
 
 
@@ -52,3 +57,52 @@ def test_after_type_change(self):
         TestNullableUniqueTogetherModel.objects.create(a='aaa', b='bbb', c='ccc')
         with self.assertRaises(IntegrityError):
             TestNullableUniqueTogetherModel.objects.create(a='aaa', b='bbb', c='ccc')
+
+
+class TestUniqueConstraints(TransactionTestCase):
+    def test_unsupportable_unique_constraint(self):
+        # Only execute tests when running against SQL Server
+        connection = connections['default']
+        if isinstance(connection, DatabaseWrapper):
+
+            class TestMigration(migrations.Migration):
+                initial = True
+
+                operations = [
+                    migrations.CreateModel(
+                        name='TestUnsupportableUniqueConstraint',
+                        fields=[
+                            (
+                                'id',
+                                models.AutoField(
+                                    auto_created=True,
+                                    primary_key=True,
+                                    serialize=False,
+                                    verbose_name='ID',
+                                ),
+                            ),
+                            ('_type', models.CharField(max_length=50)),
+                            ('status', models.CharField(max_length=50)),
+                        ],
+                    ),
+                    migrations.AddConstraint(
+                        model_name='testunsupportableuniqueconstraint',
+                        constraint=models.UniqueConstraint(
+                            condition=models.Q(
+                                ('status', 'in_progress'),
+                                ('status', 'needs_changes'),
+                                _connector='OR',
+                            ),
+                            fields=('_type',),
+                            name='or_constraint',
+                        ),
+                    ),
+                ]
+
+            migration = TestMigration('testapp', 'test_unsupportable_unique_constraint')
+
+            with connection.schema_editor(atomic=True) as editor:
+                with self.assertRaisesRegex(
+                    NotImplementedError, "does not support OR conditions"
+                ):
+                    return migration.apply(ProjectState(), editor)