Add support for unique_together

django/db/backends/schema.py

@@ -29,6 +29,7 @@ class BaseDatabaseSchemaEditor(object):
 
     # Overrideable SQL templates
     sql_create_table = "CREATE TABLE %(table)s (%(definition)s)"
+    sql_create_table_unique = "UNIQUE (%(columns)s)"
     sql_rename_table = "ALTER TABLE %(old_table)s RENAME TO %(new_table)s"
     sql_delete_table = "DROP TABLE %(table)s CASCADE"
 
@@ -51,7 +52,7 @@ class BaseDatabaseSchemaEditor(object):
     sql_create_fk = "ALTER TABLE %(table)s ADD CONSTRAINT %(name)s FOREIGN KEY (%(column)s) REFERENCES %(to_table)s (%(to_column)s) DEFERRABLE INITIALLY DEFERRED"
     sql_delete_fk = "ALTER TABLE %(table)s DROP CONSTRAINT %(name)s"
 
-    sql_create_index = "CREATE %(unique)s INDEX %(name)s ON %(table)s (%(columns)s)%s;"
+    sql_create_index = "CREATE %(unique)s INDEX %(name)s ON %(table)s (%(columns)s)%(extra)s;"
     sql_delete_index = "DROP INDEX %(name)s"
 
     sql_create_pk = "ALTER TABLE %(table)s ADD CONSTRAINT %(constraint)s PRIMARY KEY (%(columns)s)"
@@ -174,6 +175,17 @@ class BaseDatabaseSchemaEditor(object):
                 definition,
             ))
             params.extend(extra_params)
+            # Indexes
+            if field.db_index:
+                self.deferred_sql.append(
+                    self.sql_create_index % {
+                        "unique": "",
+                        "name": self._create_index_name(model, [field.column], suffix=""),
+                        "table": self.quote_name(model._meta.db_table),
+                        "columns": self.quote_name(field.column),
+                        "extra": "",
+                    }
+                )
             # FK
             if field.rel:
                 to_table = field.rel.to._meta.db_table
@@ -191,6 +203,12 @@ class BaseDatabaseSchemaEditor(object):
                         "to_column": self.quote_name(to_column),
                     }
                 )
+        # Add any unique_togethers
+        for fields in model._meta.unique_together:
+            columns = [model._meta.get_field_by_name(field)[0].column for field in fields]
+            column_sqls.append(self.sql_create_table_unique % {
+                "columns": ", ".join(self.quote_name(column) for column in columns),
+            })
         # Make the table
         sql = self.sql_create_table % {
             "table": model._meta.db_table,
@@ -210,6 +228,39 @@ class BaseDatabaseSchemaEditor(object):
             "table": self.quote_name(model._meta.db_table),
         })
 
+    def alter_unique_together(self, model, old_unique_together, new_unique_together):
+        """
+        Deals with a model changing its unique_together.
+        Note: The input unique_togethers must be doubly-nested, not the single-
+        nested ["foo", "bar"] format.
+        """
+        olds = set(frozenset(fields) for fields in old_unique_together)
+        news = set(frozenset(fields) for fields in new_unique_together)
+        # Deleted uniques
+        for fields in olds.difference(news):
+            columns = [model._meta.get_field_by_name(field)[0].column for field in fields]
+            constraint_names = self._constraint_names(model, list(columns), unique=True)
+            if len(constraint_names) != 1:
+                raise ValueError("Found wrong number (%s) of constraints for %s(%s)" % (
+                    len(constraint_names),
+                    model._meta.db_table,
+                    ", ".join(columns),
+                ))
+            self.execute(
+                self.sql_delete_unique % {
+                    "table": self.quote_name(model._meta.db_table),
+                    "name": constraint_names[0],
+                },
+            )
+        # Created uniques
+        for fields in news.difference(olds):
+            columns = [model._meta.get_field_by_name(field)[0].column for field in fields]
+            self.execute(self.sql_create_unique % {
+                "table": self.quote_name(model._meta.db_table),
+                "name": self._create_index_name(model, columns, suffix="_uniq"),
+                "columns": ", ".join(self.quote_name(column) for column in columns),
+            })
+
     def create_field(self, model, field, keep_default=False):
         """
         Creates a field on a model.

tests/modeltests/schema/models.py

@@ -32,3 +32,15 @@ class Book(models.Model):
 class Tag(models.Model):
     title = models.CharField(max_length=255)
     slug = models.SlugField(unique=True)
+
+    class Meta:
+        managed = False
+
+
+class UniqueTest(models.Model):
+    year = models.IntegerField()
+    slug = models.SlugField(unique=False)
+
+    class Meta:
+        managed = False
+        unique_together = ["year", "slug"]

tests/modeltests/schema/tests.py

@@ -6,7 +6,7 @@ from django.db import connection, DatabaseError, IntegrityError
 from django.db.models.fields import IntegerField, TextField, CharField, SlugField
 from django.db.models.fields.related import ManyToManyField
 from django.db.models.loading import cache
-from .models import Author, Book, AuthorWithM2M, Tag
+from .models import Author, Book, AuthorWithM2M, Tag, UniqueTest
 
 
 class SchemaTests(TestCase):
@@ -18,7 +18,7 @@ class SchemaTests(TestCase):
     as the code it is testing.
     """
 
-    models = [Author, Book, AuthorWithM2M, Tag]
+    models = [Author, Book, AuthorWithM2M, Tag, UniqueTest]
 
     # Utility functions
 
@@ -298,3 +298,47 @@ class SchemaTests(TestCase):
         Tag.objects.create(title="foo", slug="foo")
         self.assertRaises(IntegrityError, Tag.objects.create, title="bar", slug="foo")
         connection.rollback()
+
+    def test_unique_together(self):
+        """
+        Tests removing and adding unique_together constraints on a model.
+        """
+        # Create the table
+        editor = connection.schema_editor()
+        editor.start()
+        editor.create_model(UniqueTest)
+        editor.commit()
+        # Ensure the fields are unique to begin with
+        UniqueTest.objects.create(year=2012, slug="foo")
+        UniqueTest.objects.create(year=2011, slug="foo")
+        UniqueTest.objects.create(year=2011, slug="bar")
+        self.assertRaises(IntegrityError, UniqueTest.objects.create, year=2012, slug="foo")
+        connection.rollback()
+        # Alter the model to it's non-unique-together companion
+        editor = connection.schema_editor()
+        editor.start()
+        editor.alter_unique_together(
+            UniqueTest,
+            UniqueTest._meta.unique_together,
+            [],
+        )
+        editor.commit()
+        # Ensure the fields are no longer unique
+        UniqueTest.objects.create(year=2012, slug="foo")
+        UniqueTest.objects.create(year=2012, slug="foo")
+        connection.rollback()
+        # Alter it back
+        new_new_field = SlugField(unique=True)
+        new_new_field.set_attributes_from_name("slug")
+        editor = connection.schema_editor()
+        editor.start()
+        editor.alter_unique_together(
+            UniqueTest,
+            [],
+            UniqueTest._meta.unique_together,
+        )
+        editor.commit()
+        # Ensure the fields are unique again
+        UniqueTest.objects.create(year=2012, slug="foo")
+        self.assertRaises(IntegrityError, UniqueTest.objects.create, year=2012, slug="foo")
+        connection.rollback()