Improve migration optimizer to be able to optimize through other ops (42f8666f) · Commits · Dom Sekotill / django

django/db/migrations/operations/base.py

+12 −0

Original line number	Diff line number	Diff line
		@@ -64,6 +64,18 @@ class Operation(object):
		"""
		return "%s: %s" % (self.__class__.__name__, self._constructor_args)

		def references_model(self, name, app_label=None):
		"""
		Returns True if there is a chance this operation references the given
		model name (as a string), with an optional app label for accuracy.

		Used for optimization. If in doubt, return True;
		returning a false positive will merely make the optimizer a little
		less efficient, while returning a false negative may result in an
		unusable optimized migration.
		"""
		return True

		def __repr__(self):
		return "<%s %s%s>" % (
		self.__class__.__name__,

django/db/migrations/operations/models.py

+30 −0

Original line number	Diff line number	Diff line
		from .base import Operation
		from django.utils import six
		from django.db import models, router
		from django.db.models.options import normalize_unique_together
		from django.db.migrations.state import ModelState
		@@ -33,6 +34,23 @@ class CreateModel(Operation):
		def describe(self):
		return "Create model %s" % (self.name, )

		def references_model(self, name, app_label=None):
		strings_to_check = [self.name]
		# Check we didn't inherit from the model
		for base in self.bases:
		if isinstance(base, six.string_types):
		strings_to_check.append(base.split(".")[-1])
		# Check we have no FKs/M2Ms with it
		for fname, field in self.fields:
		if field.rel:
		if isinstance(field.rel.to, six.string_types):
		strings_to_check.append(field.rel.to.split(".")[-1])
		# Now go over all the strings and compare them
		for string in strings_to_check:
		if string.lower() == name.lower():
		return True
		return False

		def __eq__(self, other):
		return (
		(self.__class__ == other.__class__) and
		@@ -66,6 +84,9 @@ class DeleteModel(Operation):
		if router.allow_migrate(schema_editor.connection.alias, model):
		schema_editor.create_model(model)

		def references_model(self, name, app_label=None):
		return name.lower() == self.name.lower()

		def describe(self):
		return "Delete model %s" % (self.name, )

		@@ -97,6 +118,9 @@ class AlterModelTable(Operation):
		def database_backwards(self, app_label, schema_editor, from_state, to_state):
		return self.database_forwards(app_label, schema_editor, from_state, to_state)

		def references_model(self, name, app_label=None):
		return name.lower() == self.name.lower()

		def describe(self):
		return "Rename table for %s to %s" % (self.name, self.table)

		@@ -131,6 +155,9 @@ class AlterUniqueTogether(Operation):
		def database_backwards(self, app_label, schema_editor, from_state, to_state):
		return self.database_forwards(app_label, schema_editor, from_state, to_state)

		def references_model(self, name, app_label=None):
		return name.lower() == self.name.lower()

		def describe(self):
		return "Alter unique_together for %s (%s constraints)" % (self.name, len(self.unique_together))

		@@ -164,5 +191,8 @@ class AlterIndexTogether(Operation):
		def database_backwards(self, app_label, schema_editor, from_state, to_state):
		return self.database_forwards(app_label, schema_editor, from_state, to_state)

		def references_model(self, name, app_label=None):
		return name.lower() == self.name.lower()

		def describe(self):
		return "Alter index_together for %s (%s constraints)" % (self.name, len(self.index_together))

django/db/migrations/optimizer.py

+20 −5

Original line number	Diff line number	Diff line
		@@ -11,7 +11,7 @@ class MigrationOptimizer(object):
		nothing.
		"""

		def optimize(self, operations):
		def optimize(self, operations, app_label=None):
		"""
		Main optimization entry point. Pass in a list of Operation instances,
		get out a new list of Operation instances.
		@@ -27,17 +27,20 @@ class MigrationOptimizer(object):
		The inner loop is run until the starting list is the same as the result
		list, and then the result is returned. This means that operation
		optimization must be stable and always return an equal or shorter list.

		The app_label argument is optional, but if you pass it you'll get more
		efficient optimization.
		"""
		# Internal tracking variable for test assertions about # of loops
		self._iterations = 0
		while True:
		result = self.optimize_inner(operations)
		result = self.optimize_inner(operations, app_label)
		self._iterations += 1
		if result == operations:
		return result
		operations = result

		def optimize_inner(self, operations):
		def optimize_inner(self, operations, app_label=None):
		"""
		Inner optimization loop.
		"""
		@@ -52,7 +55,7 @@ class MigrationOptimizer(object):
		new_operations.extend(operations[i+1:i+1+j])
		new_operations.extend(operations[i+j+2:])
		return new_operations
		if not self.can_optimize_through(operation, other):
		if not self.can_optimize_through(operation, other, app_label):
		new_operations.append(operation)
		break
		else:
		@@ -95,10 +98,22 @@ class MigrationOptimizer(object):

		#### THROUGH CHECKS ####

		def can_optimize_through(self, operation, other):
		def can_optimize_through(self, operation, other, app_label=None):
		"""
		Returns True if it's possible to optimize 'operation' with something
		the other side of 'other'. This is possible if, for example, they
		affect different models.
		"""
		MODEL_LEVEL_OPERATIONS = (
		migrations.CreateModel,
		migrations.DeleteModel,
		migrations.AlterModelTable,
		migrations.AlterUniqueTogether,
		migrations.AlterIndexTogether,
		)
		# If it's a model level operation, let it through if there's
		# nothing that looks like a reference to us in 'other'.
		if isinstance(operation, MODEL_LEVEL_OPERATIONS):
		if not other.references_model(operation.name, app_label):
		return True
		return False

tests/migrations/test_optimizer.py

+62 −0

Original line number	Diff line number	Diff line
		@@ -93,3 +93,65 @@ class OptimizerTests(TestCase):
		],
		[],
		)

		def test_optimize_through_create(self):
		"""
		We should be able to optimize away create/delete through a create or delete
		of a different model, but only if the create operation does not mention the model
		at all.
		"""
		# These should work
		self.assertOptimizesTo(
		[
		migrations.CreateModel("Foo", [("name", models.CharField(max_length=255))]),
		migrations.CreateModel("Bar", [("size", models.IntegerField())]),
		migrations.DeleteModel("Foo"),
		],
		[
		migrations.CreateModel("Bar", [("size", models.IntegerField())]),
		],
		)
		self.assertOptimizesTo(
		[
		migrations.CreateModel("Foo", [("name", models.CharField(max_length=255))]),
		migrations.CreateModel("Bar", [("size", models.IntegerField())]),
		migrations.DeleteModel("Bar"),
		migrations.DeleteModel("Foo"),
		],
		[],
		)
		self.assertOptimizesTo(
		[
		migrations.CreateModel("Foo", [("name", models.CharField(max_length=255))]),
		migrations.CreateModel("Bar", [("size", models.IntegerField())]),
		migrations.DeleteModel("Foo"),
		migrations.DeleteModel("Bar"),
		],
		[],
		)
		# This should not work - FK should block it
		self.assertOptimizesTo(
		[
		migrations.CreateModel("Foo", [("name", models.CharField(max_length=255))]),
		migrations.CreateModel("Bar", [("other", models.ForeignKey("testapp.Foo"))]),
		migrations.DeleteModel("Foo"),
		],
		[
		migrations.CreateModel("Foo", [("name", models.CharField(max_length=255))]),
		migrations.CreateModel("Bar", [("other", models.ForeignKey("testapp.Foo"))]),
		migrations.DeleteModel("Foo"),
		],
		)
		# This should not work - bases should block it
		self.assertOptimizesTo(
		[
		migrations.CreateModel("Foo", [("name", models.CharField(max_length=255))]),
		migrations.CreateModel("Bar", [("size", models.IntegerField())], bases=("testapp.Foo", )),
		migrations.DeleteModel("Foo"),
		],
		[
		migrations.CreateModel("Foo", [("name", models.CharField(max_length=255))]),
		migrations.CreateModel("Bar", [("size", models.IntegerField())], bases=("testapp.Foo", )),
		migrations.DeleteModel("Foo"),
		],
		)