Commit 6a0d9f06 authored by Claude Paroz's avatar Claude Paroz
Browse files

[1.8.x] Fixed #24757 -- Recreated MySQL index when needed during combined index removal 

Thanks Thomas Recouvreux for the report and Tim Graham for the tests and
review.
Backport of ae635cc3 from master.
parent 30e57038

django/db/backends/base/schema.py

+13 −18
Original line number Diff line number Diff line
@@ -317,15 +317,7 @@ class BaseDatabaseSchemaEditor(object): 
        news = set(tuple(fields) for fields in new_unique_together)

        # Deleted uniques

        for fields in olds.difference(news):

            columns = [model._meta.get_field(field).column for field in fields]

            constraint_names = self._constraint_names(model, 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._delete_constraint_sql(self.sql_delete_unique, model, constraint_names[0]))

            self._delete_composed_index(model, fields, {'unique': True}, self.sql_delete_unique)

        # Created uniques

        for fields in news.difference(olds):

            columns = [model._meta.get_field(field).column for field in fields]
@@ -341,19 +333,22 @@ class BaseDatabaseSchemaEditor(object): 
        news = set(tuple(fields) for fields in new_index_together)

        # Deleted indexes

        for fields in olds.difference(news):

            self._delete_composed_index(model, fields, {'index': True}, self.sql_delete_index)

        # Created indexes

        for field_names in news.difference(olds):

            fields = [model._meta.get_field(field) for field in field_names]

            self.execute(self._create_index_sql(model, fields, suffix="_idx"))



    def _delete_composed_index(self, model, fields, constraint_kwargs, sql):

        columns = [model._meta.get_field(field).column for field in fields]

            constraint_names = self._constraint_names(model, list(columns), index=True)

        constraint_names = self._constraint_names(model, columns, **constraint_kwargs)

        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._delete_constraint_sql(self.sql_delete_index, model, constraint_names[0]))

        # Created indexes

        for field_names in news.difference(olds):

            fields = [model._meta.get_field(field) for field in field_names]

            self.execute(self._create_index_sql(model, fields, suffix="_idx"))

        self.execute(self._delete_constraint_sql(sql, model, constraint_names[0]))



    def alter_db_table(self, model, old_db_table, new_db_table):

        """

django/db/backends/mysql/schema.py

+18 −0
Original line number Diff line number Diff line
@@ -62,6 +62,24 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor): 
                    field.db_index = False

        return super(DatabaseSchemaEditor, self)._model_indexes_sql(model)



    def _delete_composed_index(self, model, fields, *args):

        """

        MySQL can remove an implicit FK index on a field when that field is

        covered by another index like a unique_together. "covered" here means

        that the more complex index starts like the simpler one.

        http://bugs.mysql.com/bug.php?id=37910 / Django ticket #24757

        We check here before removing the [unique|index]_together if we have to

        recreate a FK index.

        """

        first_field = model._meta.get_field(fields[0])

        if first_field.get_internal_type() == 'ForeignKey':

            constraint_names = self._constraint_names(model, fields[0], index=True)

            if not constraint_names:

                self.execute(

                    self._create_index_sql(model, [model._meta.get_field(fields[0])], suffix="")

                )

        return super(DatabaseSchemaEditor, self)._delete_composed_index(model, fields, *args)



    def _alter_column_type_sql(self, table, old_field, new_field, new_type):

        # Keep null property of old field, if it has changed, it will be handled separately

        if old_field.null:

docs/releases/1.8.2.txt

+3 −0
Original line number Diff line number Diff line
@@ -27,3 +27,6 @@ Bugfixes 
  :ticket:`24712`).



* Fixed ``isnull`` lookup for ``HStoreField`` (:ticket:`24751`).



* Fixed a MySQL crash when a migration removes a combined index (unique_together

  or index_together) containing a foreign key (:ticket:`24757`).

tests/schema/tests.py

+36 −0
Original line number Diff line number Diff line
@@ -1084,6 +1084,24 @@ class SchemaTests(TransactionTestCase): 
        self.assertRaises(IntegrityError, UniqueTest.objects.create, year=2012, slug="foo")

        UniqueTest.objects.all().delete()



    def test_unique_together_with_fk(self):

        """

        Tests removing and adding unique_together constraints that include

        a foreign key.

        """

        # Create the table

        with connection.schema_editor() as editor:

            editor.create_model(Author)

            editor.create_model(Book)

        # Ensure the fields are unique to begin with

        self.assertEqual(Book._meta.unique_together, ())

        # Add the unique_together constraint

        with connection.schema_editor() as editor:

            editor.alter_unique_together(Book, [], [['author', 'title']])

        # Alter it back

        with connection.schema_editor() as editor:

            editor.alter_unique_together(Book, [['author', 'title']], [])



    def test_index_together(self):

        """

        Tests removing and adding index_together constraints on a model.
@@ -1127,6 +1145,24 @@ class SchemaTests(TransactionTestCase): 
            ),

        )



    def test_index_together_with_fk(self):

        """

        Tests removing and adding index_together constraints that include

        a foreign key.

        """

        # Create the table

        with connection.schema_editor() as editor:

            editor.create_model(Author)

            editor.create_model(Book)

        # Ensure the fields are unique to begin with

        self.assertEqual(Book._meta.index_together, ())

        # Add the unique_together constraint

        with connection.schema_editor() as editor:

            editor.alter_index_together(Book, [], [['author', 'title']])

        # Alter it back

        with connection.schema_editor() as editor:

            editor.alter_index_together(Book, [['author', 'title']], [])



    def test_create_index_together(self):

        """

        Tests creating models with index_together already defined