Fixed #24757 -- Recreated MySQL index when needed during combined index removal (ae635cc3) · Commits · Dom Sekotill / django

django/db/backends/base/schema.py

+13 −18

Original line number	Diff line number	Diff line
		@@ -315,15 +315,7 @@ 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]
		@@ -339,19 +331,22 @@ 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