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Improve migration optimizer to be able to optimize through other ops

This commit is contained in:
Andrew Godwin 2013-10-16 11:09:33 +01:00
parent 694d7da6c5
commit 42f8666f6a
4 changed files with 124 additions and 5 deletions
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12
django/db/migrations/operations/base.py
View File

@ -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__,

30
django/db/migrations/operations/models.py
View File

@ -1,4 +1,5 @@
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))

25
django/db/migrations/optimizer.py
View File

@ -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

62
tests/migrations/test_optimizer.py
View File

@ -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"),
],
)