Refs #22608 -- Optimized migration optimizer and migrate by caching calls to str.lower()

5 files changed, 180 insertions, 91 deletions

diff --git a/django/db/migrations/autodetector.py b/django/db/migrations/autodetector.py
index 8535a98e73..e86e9c5f68 100644
--- a/django/db/migrations/autodetector.py
+++ b/django/db/migrations/autodetector.py
@@ -168,7 +168,7 @@ class MigrationAutodetector(object):
                         and not old_field.rel.through._meta.auto_created):
                     through_key = (
                         old_field.rel.through._meta.app_label,
-                        old_field.rel.through._meta.object_name.lower(),
+                        old_field.rel.through._meta.model_name,
                     )
                     self.through_users[through_key] = (app_label, old_model_name, field_name)
 
@@ -322,47 +322,47 @@ class MigrationAutodetector(object):
         if dependency[2] is None and dependency[3] is True:
             return (
                 isinstance(operation, operations.CreateModel) and
-                operation.name.lower() == dependency[1].lower()
+                operation.name_lower == dependency[1].lower()
             )
         # Created field
         elif dependency[2] is not None and dependency[3] is True:
             return (
                 (
                     isinstance(operation, operations.CreateModel) and
-                    operation.name.lower() == dependency[1].lower() and
+                    operation.name_lower == dependency[1].lower() and
                     any(dependency[2] == x for x, y in operation.fields)
                 ) or
                 (
                     isinstance(operation, operations.AddField) and
-                    operation.model_name.lower() == dependency[1].lower() and
-                    operation.name.lower() == dependency[2].lower()
+                    operation.model_name_lower == dependency[1].lower() and
+                    operation.name_lower == dependency[2].lower()
                 )
             )
         # Removed field
         elif dependency[2] is not None and dependency[3] is False:
             return (
                 isinstance(operation, operations.RemoveField) and
-                operation.model_name.lower() == dependency[1].lower() and
-                operation.name.lower() == dependency[2].lower()
+                operation.model_name_lower == dependency[1].lower() and
+                operation.name_lower == dependency[2].lower()
             )
         # Removed model
         elif dependency[2] is None and dependency[3] is False:
             return (
                 isinstance(operation, operations.DeleteModel) and
-                operation.name.lower() == dependency[1].lower()
+                operation.name_lower == dependency[1].lower()
             )
         # Field being altered
         elif dependency[2] is not None and dependency[3] == "alter":
             return (
                 isinstance(operation, operations.AlterField) and
-                operation.model_name.lower() == dependency[1].lower() and
-                operation.name.lower() == dependency[2].lower()
+                operation.model_name_lower == dependency[1].lower() and
+                operation.name_lower == dependency[2].lower()
             )
         # order_with_respect_to being unset for a field
         elif dependency[2] is not None and dependency[3] == "order_wrt_unset":
             return (
                 isinstance(operation, operations.AlterOrderWithRespectTo) and
-                operation.name.lower() == dependency[1].lower() and
+                operation.name_lower == dependency[1].lower() and
                 (operation.order_with_respect_to or "").lower() != dependency[2].lower()
             )
         # Field is removed and part of an index/unique_together
@@ -370,7 +370,7 @@ class MigrationAutodetector(object):
             return (
                 isinstance(operation, (operations.AlterUniqueTogether,
                                        operations.AlterIndexTogether)) and
-                operation.name.lower() == dependency[1].lower()
+                operation.name_lower == dependency[1].lower()
             )
         # Unknown dependency. Raise an error.
         else:
@@ -696,7 +696,7 @@ class MigrationAutodetector(object):
             for name, field in sorted(related_fields.items()):
                 dependencies.append((app_label, model_name, name, False))
             # We're referenced in another field's through=
-            through_user = self.through_users.get((app_label, model_state.name.lower()), None)
+            through_user = self.through_users.get((app_label, model_state.name_lower), None)
             if through_user:
                 dependencies.append((through_user[0], through_user[1], through_user[2], False))
             # Finally, make the operation, deduping any dependencies
@@ -842,7 +842,7 @@ class MigrationAutodetector(object):
             if hasattr(new_field, "rel") and getattr(new_field.rel, "to", None):
                 rename_key = (
                     new_field.rel.to._meta.app_label,
-                    new_field.rel.to._meta.object_name.lower(),
+                    new_field.rel.to._meta.model_name,
                 )
                 if rename_key in self.renamed_models:
                     new_field.rel.to = old_field.rel.to
@@ -1094,16 +1094,16 @@ class MigrationAutodetector(object):
         """
         if len(ops) == 1:
             if isinstance(ops[0], operations.CreateModel):
-                return ops[0].name.lower()
+                return ops[0].name_lower
             elif isinstance(ops[0], operations.DeleteModel):
-                return "delete_%s" % ops[0].name.lower()
+                return "delete_%s" % ops[0].name_lower
             elif isinstance(ops[0], operations.AddField):
-                return "%s_%s" % (ops[0].model_name.lower(), ops[0].name.lower())
+                return "%s_%s" % (ops[0].model_name_lower, ops[0].name_lower)
             elif isinstance(ops[0], operations.RemoveField):
-                return "remove_%s_%s" % (ops[0].model_name.lower(), ops[0].name.lower())
+                return "remove_%s_%s" % (ops[0].model_name_lower, ops[0].name_lower)
         elif len(ops) > 1:
             if all(isinstance(o, operations.CreateModel) for o in ops):
-                return "_".join(sorted(o.name.lower() for o in ops))
+                return "_".join(sorted(o.name_lower for o in ops))
         return "auto_%s" % datetime.datetime.now().strftime("%Y%m%d_%H%M")
 
     @classmethod
diff --git a/django/db/migrations/operations/fields.py b/django/db/migrations/operations/fields.py
index 6ce5e37296..ea9dffff1f 100644
--- a/django/db/migrations/operations/fields.py
+++ b/django/db/migrations/operations/fields.py
@@ -2,6 +2,7 @@ from __future__ import unicode_literals
 
 from django.db.models.fields import NOT_PROVIDED
 from django.utils import six
+from django.utils.functional import cached_property
 from .base import Operation
 
 
@@ -16,6 +17,14 @@ class AddField(Operation):
         self.field = field
         self.preserve_default = preserve_default
 
+    @cached_property
+    def name_lower(self):
+        return self.name.lower()
+
+    @cached_property
+    def model_name_lower(self):
+        return self.model_name.lower()
+
     def deconstruct(self):
         kwargs = {
             'model_name': self.model_name,
@@ -37,8 +46,8 @@ class AddField(Operation):
             field.default = NOT_PROVIDED
         else:
             field = self.field
-        state.models[app_label, self.model_name.lower()].fields.append((self.name, field))
-        state.reload_model(app_label, self.model_name)
+        state.models[app_label, self.model_name_lower].fields.append((self.name, field))
+        state.reload_model(app_label, self.model_name_lower)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.model_name)
@@ -63,10 +72,10 @@ class AddField(Operation):
         return "Add field %s to %s" % (self.name, self.model_name)
 
     def references_model(self, name, app_label=None):
-        return name.lower() == self.model_name.lower()
+        return name.lower() == self.model_name_lower
 
     def references_field(self, model_name, name, app_label=None):
-        return self.references_model(model_name) and name.lower() == self.name.lower()
+        return self.references_model(model_name) and name.lower() == self.name_lower
 
 
 class RemoveField(Operation):
@@ -78,6 +87,14 @@ class RemoveField(Operation):
         self.model_name = model_name
         self.name = name
 
+    @cached_property
+    def name_lower(self):
+        return self.name.lower()
+
+    @cached_property
+    def model_name_lower(self):
+        return self.model_name.lower()
+
     def deconstruct(self):
         kwargs = {
             'model_name': self.model_name,
@@ -91,11 +108,11 @@ class RemoveField(Operation):
 
     def state_forwards(self, app_label, state):
         new_fields = []
-        for name, instance in state.models[app_label, self.model_name.lower()].fields:
+        for name, instance in state.models[app_label, self.model_name_lower].fields:
             if name != self.name:
                 new_fields.append((name, instance))
-        state.models[app_label, self.model_name.lower()].fields = new_fields
-        state.reload_model(app_label, self.model_name)
+        state.models[app_label, self.model_name_lower].fields = new_fields
+        state.reload_model(app_label, self.model_name_lower)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         from_model = from_state.apps.get_model(app_label, self.model_name)
@@ -112,10 +129,10 @@ class RemoveField(Operation):
         return "Remove field %s from %s" % (self.name, self.model_name)
 
     def references_model(self, name, app_label=None):
-        return name.lower() == self.model_name.lower()
+        return name.lower() == self.model_name_lower
 
     def references_field(self, model_name, name, app_label=None):
-        return self.references_model(model_name) and name.lower() == self.name.lower()
+        return self.references_model(model_name) and name.lower() == self.name_lower
 
 
 class AlterField(Operation):
@@ -129,6 +146,14 @@ class AlterField(Operation):
         self.field = field
         self.preserve_default = preserve_default
 
+    @cached_property
+    def name_lower(self):
+        return self.name.lower()
+
+    @cached_property
+    def model_name_lower(self):
+        return self.model_name.lower()
+
     def deconstruct(self):
         kwargs = {
             'model_name': self.model_name,
@@ -149,10 +174,12 @@ class AlterField(Operation):
             field.default = NOT_PROVIDED
         else:
             field = self.field
-        state.models[app_label, self.model_name.lower()].fields = [
-            (n, field if n == self.name else f) for n, f in state.models[app_label, self.model_name.lower()].fields
+        state.models[app_label, self.model_name_lower].fields = [
+            (n, field if n == self.name else f)
+            for n, f in
+            state.models[app_label, self.model_name_lower].fields
         ]
-        state.reload_model(app_label, self.model_name)
+        state.reload_model(app_label, self.model_name_lower)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.model_name)
@@ -181,10 +208,10 @@ class AlterField(Operation):
         return "Alter field %s on %s" % (self.name, self.model_name)
 
     def references_model(self, name, app_label=None):
-        return name.lower() == self.model_name.lower()
+        return name.lower() == self.model_name_lower
 
     def references_field(self, model_name, name, app_label=None):
-        return self.references_model(model_name) and name.lower() == self.name.lower()
+        return self.references_model(model_name) and name.lower() == self.name_lower
 
 
 class RenameField(Operation):
@@ -197,6 +224,18 @@ class RenameField(Operation):
         self.old_name = old_name
         self.new_name = new_name
 
+    @cached_property
+    def old_name_lower(self):
+        return self.old_name.lower()
+
+    @cached_property
+    def new_name_lower(self):
+        return self.new_name.lower()
+
+    @cached_property
+    def model_name_lower(self):
+        return self.model_name.lower()
+
     def deconstruct(self):
         kwargs = {
             'model_name': self.model_name,
@@ -211,19 +250,19 @@ class RenameField(Operation):
 
     def state_forwards(self, app_label, state):
         # Rename the field
-        state.models[app_label, self.model_name.lower()].fields = [
+        state.models[app_label, self.model_name_lower].fields = [
             (self.new_name if n == self.old_name else n, f)
-            for n, f in state.models[app_label, self.model_name.lower()].fields
+            for n, f in state.models[app_label, self.model_name_lower].fields
         ]
         # Fix index/unique_together to refer to the new field
-        options = state.models[app_label, self.model_name.lower()].options
+        options = state.models[app_label, self.model_name_lower].options
         for option in ('index_together', 'unique_together'):
             if option in options:
                 options[option] = [
                     [self.new_name if n == self.old_name else n for n in together]
                     for together in options[option]
                 ]
-        state.reload_model(app_label, self.model_name)
+        state.reload_model(app_label, self.model_name_lower)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.model_name)
@@ -249,10 +288,10 @@ class RenameField(Operation):
         return "Rename field %s on %s to %s" % (self.old_name, self.model_name, self.new_name)
 
     def references_model(self, name, app_label=None):
-        return name.lower() == self.model_name.lower()
+        return name.lower() == self.model_name_lower
 
     def references_field(self, model_name, name, app_label=None):
         return self.references_model(model_name) and (
-            name.lower() == self.old_name.lower() or
-            name.lower() == self.new_name.lower()
+            name.lower() == self.old_name_lower or
+            name.lower() == self.new_name_lower
         )
diff --git a/django/db/migrations/operations/models.py b/django/db/migrations/operations/models.py
index 6dd66ae454..773c70526f 100644
--- a/django/db/migrations/operations/models.py
+++ b/django/db/migrations/operations/models.py
@@ -5,6 +5,7 @@ from django.db.models.options import normalize_together
 from django.db.migrations.state import ModelState
 from django.db.migrations.operations.base import Operation
 from django.utils import six
+from django.utils.functional import cached_property
 
 
 class CreateModel(Operation):
@@ -21,6 +22,10 @@ class CreateModel(Operation):
         self.bases = bases or (models.Model,)
         self.managers = managers or []
 
+    @cached_property
+    def name_lower(self):
+        return self.name.lower()
+
     def deconstruct(self):
         kwargs = {
             'name': self.name,
@@ -87,6 +92,10 @@ class DeleteModel(Operation):
     def __init__(self, name):
         self.name = name
 
+    @cached_property
+    def name_lower(self):
+        return self.name.lower()
+
     def deconstruct(self):
         kwargs = {
             'name': self.name,
@@ -98,7 +107,7 @@ class DeleteModel(Operation):
         )
 
     def state_forwards(self, app_label, state):
-        state.remove_model(app_label, self.name)
+        state.remove_model(app_label, self.name_lower)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         model = from_state.apps.get_model(app_label, self.name)
@@ -111,7 +120,7 @@ class DeleteModel(Operation):
             schema_editor.create_model(model)
 
     def references_model(self, name, app_label=None):
-        return name.lower() == self.name.lower()
+        return name.lower() == self.name_lower
 
     def describe(self):
         return "Delete model %s" % (self.name, )
@@ -126,6 +135,14 @@ class RenameModel(Operation):
         self.old_name = old_name
         self.new_name = new_name
 
+    @cached_property
+    def old_name_lower(self):
+        return self.old_name.lower()
+
+    @cached_property
+    def new_name_lower(self):
+        return self.new_name.lower()
+
     def deconstruct(self):
         kwargs = {
             'old_name': self.old_name,
@@ -147,18 +164,18 @@ class RenameModel(Operation):
             if f.auto_created and not f.concrete and not (f.hidden or f.many_to_many)
         )
         # Rename the model
-        state.models[app_label, self.new_name.lower()] = state.models[app_label, self.old_name.lower()]
-        state.models[app_label, self.new_name.lower()].name = self.new_name
-        state.remove_model(app_label, self.old_name)
+        state.models[app_label, self.new_name_lower] = state.models[app_label, self.old_name_lower]
+        state.models[app_label, self.new_name_lower].name = self.new_name
+        state.remove_model(app_label, self.old_name_lower)
         # Repoint the FKs and M2Ms pointing to us
         for related_object in all_related_objects:
             # Use the new related key for self referential related objects.
             if related_object.related_model == model:
-                related_key = (app_label, self.new_name.lower())
+                related_key = (app_label, self.new_name_lower)
             else:
                 related_key = (
                     related_object.related_model._meta.app_label,
-                    related_object.related_model._meta.object_name.lower(),
+                    related_object.related_model._meta.model_name,
                 )
             new_fields = []
             for name, field in state.models[related_key].fields:
@@ -168,7 +185,7 @@ class RenameModel(Operation):
                 new_fields.append((name, field))
             state.models[related_key].fields = new_fields
             state.reload_model(*related_key)
-        state.reload_model(app_label, self.new_name)
+        state.reload_model(app_label, self.new_name_lower)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         new_model = to_state.apps.get_model(app_label, self.new_name)
@@ -184,12 +201,12 @@ class RenameModel(Operation):
             for related_object in old_model._meta.related_objects:
                 if related_object.related_model == old_model:
                     model = new_model
-                    related_key = (app_label, self.new_name.lower())
+                    related_key = (app_label, self.new_name_lower)
                 else:
                     model = related_object.related_model
                     related_key = (
                         related_object.related_model._meta.app_label,
-                        related_object.related_model._meta.object_name.lower(),
+                        related_object.related_model._meta.model_name,
                     )
                 to_field = to_state.apps.get_model(
                     *related_key
@@ -201,14 +218,18 @@ class RenameModel(Operation):
                 )
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
+        self.new_name_lower, self.old_name_lower = self.old_name_lower, self.new_name_lower
         self.new_name, self.old_name = self.old_name, self.new_name
+
         self.database_forwards(app_label, schema_editor, from_state, to_state)
+
+        self.new_name_lower, self.old_name_lower = self.old_name_lower, self.new_name_lower
         self.new_name, self.old_name = self.old_name, self.new_name
 
     def references_model(self, name, app_label=None):
         return (
-            name.lower() == self.old_name.lower() or
-            name.lower() == self.new_name.lower()
+            name.lower() == self.old_name_lower or
+            name.lower() == self.new_name_lower
         )
 
     def describe(self):
@@ -224,6 +245,10 @@ class AlterModelTable(Operation):
         self.name = name
         self.table = table
 
+    @cached_property
+    def name_lower(self):
+        return self.name.lower()
+
     def deconstruct(self):
         kwargs = {
             'name': self.name,
@@ -236,8 +261,8 @@ class AlterModelTable(Operation):
         )
 
     def state_forwards(self, app_label, state):
-        state.models[app_label, self.name.lower()].options["db_table"] = self.table
-        state.reload_model(app_label, self.name)
+        state.models[app_label, self.name_lower].options["db_table"] = self.table
+        state.reload_model(app_label, self.name_lower)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         new_model = to_state.apps.get_model(app_label, self.name)
@@ -261,7 +286,7 @@ class AlterModelTable(Operation):
         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()
+        return name.lower() == self.name_lower
 
     def describe(self):
         return "Rename table for %s to %s" % (self.name, self.table)
@@ -279,6 +304,10 @@ class AlterUniqueTogether(Operation):
         unique_together = normalize_together(unique_together)
         self.unique_together = set(tuple(cons) for cons in unique_together)
 
+    @cached_property
+    def name_lower(self):
+        return self.name.lower()
+
     def deconstruct(self):
         kwargs = {
             'name': self.name,
@@ -291,9 +320,9 @@ class AlterUniqueTogether(Operation):
         )
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.name.lower()]
+        model_state = state.models[app_label, self.name_lower]
         model_state.options[self.option_name] = self.unique_together
-        state.reload_model(app_label, self.name)
+        state.reload_model(app_label, self.name_lower)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         new_model = to_state.apps.get_model(app_label, self.name)
@@ -309,7 +338,7 @@ class AlterUniqueTogether(Operation):
         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()
+        return name.lower() == self.name_lower
 
     def describe(self):
         return "Alter %s for %s (%s constraint(s))" % (self.option_name, self.name, len(self.unique_together or ''))
@@ -327,6 +356,10 @@ class AlterIndexTogether(Operation):
         index_together = normalize_together(index_together)
         self.index_together = set(tuple(cons) for cons in index_together)
 
+    @cached_property
+    def name_lower(self):
+        return self.name.lower()
+
     def deconstruct(self):
         kwargs = {
             'name': self.name,
@@ -339,9 +372,9 @@ class AlterIndexTogether(Operation):
         )
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.name.lower()]
+        model_state = state.models[app_label, self.name_lower]
         model_state.options[self.option_name] = self.index_together
-        state.reload_model(app_label, self.name)
+        state.reload_model(app_label, self.name_lower)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         new_model = to_state.apps.get_model(app_label, self.name)
@@ -357,7 +390,7 @@ class AlterIndexTogether(Operation):
         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()
+        return name.lower() == self.name_lower
 
     def describe(self):
         return "Alter %s for %s (%s constraint(s))" % (self.option_name, self.name, len(self.index_together or ''))
@@ -372,6 +405,10 @@ class AlterOrderWithRespectTo(Operation):
         self.name = name
         self.order_with_respect_to = order_with_respect_to
 
+    @cached_property
+    def name_lower(self):
+        return self.name.lower()
+
     def deconstruct(self):
         kwargs = {
             'name': self.name,
@@ -384,9 +421,9 @@ class AlterOrderWithRespectTo(Operation):
         )
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.name.lower()]
+        model_state = state.models[app_label, self.name_lower]
         model_state.options['order_with_respect_to'] = self.order_with_respect_to
-        state.reload_model(app_label, self.name)
+        state.reload_model(app_label, self.name_lower)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.name)
@@ -410,7 +447,7 @@ class AlterOrderWithRespectTo(Operation):
         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()
+        return name.lower() == self.name_lower
 
     def describe(self):
         return "Set order_with_respect_to on %s to %s" % (self.name, self.order_with_respect_to)
@@ -439,6 +476,10 @@ class AlterModelOptions(Operation):
         self.name = name
         self.options = options
 
+    @cached_property
+    def name_lower(self):
+        return self.name.lower()
+
     def deconstruct(self):
         kwargs = {
             'name': self.name,
@@ -451,13 +492,13 @@ class AlterModelOptions(Operation):
         )
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.name.lower()]
+        model_state = state.models[app_label, self.name_lower]
         model_state.options = dict(model_state.options)
         model_state.options.update(self.options)
         for key in self.ALTER_OPTION_KEYS:
             if key not in self.options and key in model_state.options:
                 del model_state.options[key]
-        state.reload_model(app_label, self.name)
+        state.reload_model(app_label, self.name_lower)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         pass
@@ -466,7 +507,7 @@ class AlterModelOptions(Operation):
         pass
 
     def references_model(self, name, app_label=None):
-        return name.lower() == self.name.lower()
+        return name.lower() == self.name_lower
 
     def describe(self):
         return "Change Meta options on %s" % (self.name, )
@@ -483,6 +524,10 @@ class AlterModelManagers(Operation):
         self.name = name
         self.managers = managers
 
+    @cached_property
+    def name_lower(self):
+        return self.name.lower()
+
     def deconstruct(self):
         return (
             self.__class__.__name__,
@@ -491,7 +536,7 @@ class AlterModelManagers(Operation):
         )
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.name.lower()]
+        model_state = state.models[app_label, self.name_lower]
         model_state.managers = list(self.managers)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
@@ -501,7 +546,7 @@ class AlterModelManagers(Operation):
         pass
 
     def references_model(self, name, app_label=None):
-        return name.lower() == self.name.lower()
+        return name.lower() == self.name_lower
 
     def describe(self):
         return "Change managers on %s" % (self.name, )
diff --git a/django/db/migrations/optimizer.py b/django/db/migrations/optimizer.py
index d48ebcf90c..be3983719e 100644
--- a/django/db/migrations/optimizer.py
+++ b/django/db/migrations/optimizer.py
@@ -177,7 +177,7 @@ class MigrationOptimizer(object):
         """
         Folds a CreateModel and a DeleteModel into nothing.
         """
-        if (operation.name.lower() == other.name.lower() and
+        if (operation.name_lower == other.name_lower and
                 not operation.options.get("proxy", False)):
             return []
 
@@ -185,14 +185,14 @@ class MigrationOptimizer(object):
         """
         Folds an AlterModelSomething and a DeleteModel into just delete.
         """
-        if operation.name.lower() == other.name.lower():
+        if operation.name_lower == other.name_lower:
             return [other]
 
     def reduce_model_create_rename(self, operation, other, in_between):
         """
         Folds a model rename into its create
         """
-        if operation.name.lower() == other.old_name.lower():
+        if operation.name_lower == other.old_name_lower:
             return [
                 migrations.CreateModel(
                     other.new_name,
@@ -206,7 +206,7 @@ class MigrationOptimizer(object):
         """
         Folds a model rename into another one
         """
-        if operation.new_name.lower() == other.old_name.lower():
+        if operation.new_name_lower == other.old_name_lower:
             return [
                 migrations.RenameModel(
                     operation.old_name,
@@ -215,7 +215,7 @@ class MigrationOptimizer(object):
             ]
 
     def reduce_create_model_add_field(self, operation, other, in_between):
-        if operation.name.lower() == other.model_name.lower():
+        if operation.name_lower == other.model_name_lower:
             # Don't allow optimisations of FKs through models they reference
             if hasattr(other.field, "rel") and other.field.rel:
                 for between in in_between:
@@ -239,7 +239,7 @@ class MigrationOptimizer(object):
             ]
 
     def reduce_create_model_alter_field(self, operation, other, in_between):
-        if operation.name.lower() == other.model_name.lower():
+        if operation.name_lower == other.model_name_lower:
             return [
                 migrations.CreateModel(
                     operation.name,
@@ -253,7 +253,7 @@ class MigrationOptimizer(object):
             ]
 
     def reduce_create_model_rename_field(self, operation, other, in_between):
-        if operation.name.lower() == other.model_name.lower():
+        if operation.name_lower == other.model_name_lower:
             return [
                 migrations.CreateModel(
                     operation.name,
@@ -267,14 +267,14 @@ class MigrationOptimizer(object):
             ]
 
     def reduce_create_model_remove_field(self, operation, other, in_between):
-        if operation.name.lower() == other.model_name.lower():
+        if operation.name_lower == other.model_name_lower:
             return [
                 migrations.CreateModel(
                     operation.name,
                     fields=[
                         (n, v)
                         for n, v in operation.fields
-                        if n.lower() != other.name.lower()
+                        if n.lower() != other.name_lower
                     ],
                     options=operation.options,
                     bases=operation.bases,
@@ -282,7 +282,8 @@ class MigrationOptimizer(object):
             ]
 
     def reduce_add_field_alter_field(self, operation, other, in_between):
-        if operation.model_name.lower() == other.model_name.lower() and operation.name.lower() == other.name.lower():
+        if (operation.model_name_lower == other.model_name_lower and
+                operation.name_lower == other.name_lower):
             return [
                 migrations.AddField(
                     model_name=operation.model_name,
@@ -292,16 +293,18 @@ class MigrationOptimizer(object):
             ]
 
     def reduce_add_field_delete_field(self, operation, other, in_between):
-        if operation.model_name.lower() == other.model_name.lower() and operation.name.lower() == other.name.lower():
+        if (operation.model_name_lower == other.model_name_lower and
+                operation.name_lower == other.name_lower):
             return []
 
     def reduce_alter_field_delete_field(self, operation, other, in_between):
-        if operation.model_name.lower() == other.model_name.lower() and operation.name.lower() == other.name.lower():
+        if (operation.model_name_lower == other.model_name_lower and
+                operation.name_lower == other.name_lower):
             return [other]
 
     def reduce_add_field_rename_field(self, operation, other, in_between):
-        if (operation.model_name.lower() == other.model_name.lower() and
-                operation.name.lower() == other.old_name.lower()):
+        if (operation.model_name_lower == other.model_name_lower and
+                operation.name_lower == other.old_name_lower):
             return [
                 migrations.AddField(
                     model_name=operation.model_name,
@@ -311,8 +314,8 @@ class MigrationOptimizer(object):
             ]
 
     def reduce_alter_field_rename_field(self, operation, other, in_between):
-        if (operation.model_name.lower() == other.model_name.lower() and
-                operation.name.lower() == other.old_name.lower()):
+        if (operation.model_name_lower == other.model_name_lower and
+                operation.name_lower == other.old_name_lower):
             return [
                 other,
                 migrations.AlterField(
@@ -323,8 +326,8 @@ class MigrationOptimizer(object):
             ]
 
     def reduce_rename_field_self(self, operation, other, in_between):
-        if (operation.model_name.lower() == other.model_name.lower() and
-                operation.new_name.lower() == other.old_name.lower()):
+        if (operation.model_name_lower == other.model_name_lower and
+                operation.new_name_lower == other.old_name_lower):
             return [
                 migrations.RenameField(
                     operation.model_name,
diff --git a/django/db/migrations/state.py b/django/db/migrations/state.py
index 6626e31442..84b8c0dbe9 100644
--- a/django/db/migrations/state.py
+++ b/django/db/migrations/state.py
@@ -33,13 +33,12 @@ class ProjectState(object):
         self.real_apps = real_apps or []
 
     def add_model(self, model_state):
-        app_label, model_name = model_state.app_label, model_state.name.lower()
+        app_label, model_name = model_state.app_label, model_state.name_lower
         self.models[(app_label, model_name)] = model_state
         if 'apps' in self.__dict__:  # hasattr would cache the property
             self.reload_model(app_label, model_name)
 
     def remove_model(self, app_label, model_name):
-        model_name = model_name.lower()
         del self.models[app_label, model_name]
         if 'apps' in self.__dict__:  # hasattr would cache the property
             self.apps.unregister_model(app_label, model_name)
@@ -47,7 +46,6 @@ class ProjectState(object):
     def reload_model(self, app_label, model_name):
         if 'apps' in self.__dict__:  # hasattr would cache the property
             # Get relations before reloading the models, as _meta.apps may change
-            model_name = model_name.lower()
             try:
                 related_old = {
                     f.related_model for f in
@@ -94,7 +92,7 @@ class ProjectState(object):
         app_models = {}
         for model in apps.get_models(include_swapped=True):
             model_state = ModelState.from_model(model)
-            app_models[(model_state.app_label, model_state.name.lower())] = model_state
+            app_models[(model_state.app_label, model_state.name_lower)] = model_state
         return cls(app_models)
 
     def __eq__(self, other):
@@ -240,6 +238,10 @@ class ModelState(object):
                     'ModelState.fields cannot be bound to a model - "%s" is.' % name
                 )
 
+    @cached_property
+    def name_lower(self):
+        return self.name.lower()
+
     @classmethod
     def from_model(cls, model, exclude_rels=False):
         """