Fixed #34529, Refs #34525 -- Reduced index operations with Meta.indexes/index_together when optimizing migrations.

This makes squashing migrations an available path for changing
Meta.index_together, which is deprecated, to Meta.indexes.

Follow up to f81032572107846922745b68d5b7191058fdd5f5.

5 files changed, 326 insertions, 68 deletions

diff --git a/django/db/migrations/operations/models.py b/django/db/migrations/operations/models.py
index b89b6b511b..9c5bd5fbcb 100644
--- a/django/db/migrations/operations/models.py
+++ b/django/db/migrations/operations/models.py
@@ -303,6 +303,71 @@ class CreateModel(ModelOperation):
                         managers=self.managers,
                     ),
                 ]
+        elif (
+            isinstance(operation, IndexOperation)
+            and self.name_lower == operation.model_name_lower
+        ):
+            if isinstance(operation, AddIndex):
+                return [
+                    CreateModel(
+                        self.name,
+                        fields=self.fields,
+                        options={
+                            **self.options,
+                            "indexes": [
+                                *self.options.get("indexes", []),
+                                operation.index,
+                            ],
+                        },
+                        bases=self.bases,
+                        managers=self.managers,
+                    ),
+                ]
+            elif isinstance(operation, RemoveIndex):
+                options_indexes = [
+                    index
+                    for index in self.options.get("indexes", [])
+                    if index.name != operation.name
+                ]
+                return [
+                    CreateModel(
+                        self.name,
+                        fields=self.fields,
+                        options={
+                            **self.options,
+                            "indexes": options_indexes,
+                        },
+                        bases=self.bases,
+                        managers=self.managers,
+                    ),
+                ]
+            elif isinstance(operation, RenameIndex) and operation.old_fields:
+                options_index_together = {
+                    fields
+                    for fields in self.options.get("index_together", [])
+                    if fields != operation.old_fields
+                }
+                if options_index_together:
+                    self.options["index_together"] = options_index_together
+                else:
+                    self.options.pop("index_together", None)
+                return [
+                    CreateModel(
+                        self.name,
+                        fields=self.fields,
+                        options={
+                            **self.options,
+                            "indexes": [
+                                *self.options.get("indexes", []),
+                                models.Index(
+                                    fields=operation.old_fields, name=operation.new_name
+                                ),
+                            ],
+                        },
+                        bases=self.bases,
+                        managers=self.managers,
+                    ),
+                ]
         return super().reduce(operation, app_label)
 
 
diff --git a/docs/releases/4.2.1.txt b/docs/releases/4.2.1.txt
index a1130effe8..bed64f6ad1 100644
--- a/docs/releases/4.2.1.txt
+++ b/docs/releases/4.2.1.txt
@@ -53,3 +53,8 @@ Bugfixes
 
 * Fixed a regression in Django 4.2 where breadcrumbs didn't appear on admin
   site app index views (:ticket:`34512`).
+
+* Made squashing migrations reduce ``AddIndex``, ``RemoveIndex``,
+  ``RenameIndex``, and ``CreateModel`` operations which allows removing a
+  deprecated ``Meta.index_together`` option from historical migrations and use
+  ``Meta.indexes`` instead (:ticket:`34525`).
diff --git a/docs/releases/4.2.txt b/docs/releases/4.2.txt
index d923be55b8..7d7848708d 100644
--- a/docs/releases/4.2.txt
+++ b/docs/releases/4.2.txt
@@ -502,7 +502,8 @@ Should become::
 
 Running the :djadmin:`makemigrations` command will generate a migration
 containing a :class:`~django.db.migrations.operations.RenameIndex` operation
-which will rename the existing index.
+which will rename the existing index. Next, consider squashing migrations to
+remove ``index_together`` from historical migrations.
 
 The ``AlterIndexTogether`` migration operation is now officially supported only
 for pre-Django 4.2 migration files. For backward compatibility reasons, it's
diff --git a/tests/migrations/test_autodetector.py b/tests/migrations/test_autodetector.py
index 44923a3c2e..ee199fea68 100644
--- a/tests/migrations/test_autodetector.py
+++ b/tests/migrations/test_autodetector.py
@@ -2266,10 +2266,9 @@ class AutodetectorTests(BaseAutodetectorTests):
             changes,
             "eggs",
             0,
-            ["CreateModel", "CreateModel", "AddIndex", "AlterUniqueTogether"],
+            ["CreateModel", "CreateModel"],
         )
         self.assertNotIn("unique_together", changes["eggs"][0].operations[0].options)
-        self.assertNotIn("unique_together", changes["eggs"][0].operations[1].options)
         self.assertMigrationDependencies(changes, "eggs", 0, [])
 
     def test_alter_db_table_add(self):
@@ -2565,6 +2564,9 @@ class AutodetectorTests(BaseAutodetectorTests):
 
     def test_create_model_with_indexes(self):
         """Test creation of new model with indexes already defined."""
+        added_index = models.Index(
+            fields=["name"], name="create_model_with_indexes_idx"
+        )
         author = ModelState(
             "otherapp",
             "Author",
@@ -2573,25 +2575,25 @@ class AutodetectorTests(BaseAutodetectorTests):
                 ("name", models.CharField(max_length=200)),
             ],
             {
-                "indexes": [
-                    models.Index(fields=["name"], name="create_model_with_indexes_idx")
-                ]
+                "indexes": [added_index],
             },
         )
         changes = self.get_changes([], [author])
-        added_index = models.Index(
-            fields=["name"], name="create_model_with_indexes_idx"
-        )
         # Right number of migrations?
         self.assertEqual(len(changes["otherapp"]), 1)
         # Right number of actions?
         migration = changes["otherapp"][0]
-        self.assertEqual(len(migration.operations), 2)
+        self.assertEqual(len(migration.operations), 1)
         # Right actions order?
-        self.assertOperationTypes(changes, "otherapp", 0, ["CreateModel", "AddIndex"])
+        self.assertOperationTypes(changes, "otherapp", 0, ["CreateModel"])
         self.assertOperationAttributes(changes, "otherapp", 0, 0, name="Author")
         self.assertOperationAttributes(
-            changes, "otherapp", 0, 1, model_name="author", index=added_index
+            changes,
+            "otherapp",
+            0,
+            0,
+            name="Author",
+            options={"indexes": [added_index]},
         )
 
     def test_add_indexes(self):
@@ -4043,62 +4045,69 @@ class AutodetectorTests(BaseAutodetectorTests):
             },
         )
 
-    def test_add_model_order_with_respect_to_index_constraint(self):
-        tests = [
-            (
-                "AddIndex",
-                {
-                    "indexes": [
-                        models.Index(fields=["_order"], name="book_order_idx"),
-                    ]
-                },
-            ),
-            (
-                "AddConstraint",
-                {
-                    "constraints": [
-                        models.CheckConstraint(
-                            check=models.Q(_order__gt=1),
-                            name="book_order_gt_1",
-                        ),
-                    ]
-                },
-            ),
-        ]
-        for operation, extra_option in tests:
-            with self.subTest(operation=operation):
-                after = ModelState(
-                    "testapp",
-                    "Author",
-                    [
-                        ("id", models.AutoField(primary_key=True)),
-                        ("name", models.CharField(max_length=200)),
-                        ("book", models.ForeignKey("otherapp.Book", models.CASCADE)),
-                    ],
-                    options={
-                        "order_with_respect_to": "book",
-                        **extra_option,
-                    },
-                )
-                changes = self.get_changes([], [self.book, after])
-                self.assertNumberMigrations(changes, "testapp", 1)
-                self.assertOperationTypes(
-                    changes,
-                    "testapp",
-                    0,
-                    [
-                        "CreateModel",
-                        operation,
-                    ],
-                )
-                self.assertOperationAttributes(
-                    changes,
-                    "testapp",
-                    0,
-                    0,
-                    name="Author",
-                    options={"order_with_respect_to": "book"},
-                )
+    def test_add_model_order_with_respect_to_constraint(self):
+        after = ModelState(
+            "testapp",
+            "Author",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                ("name", models.CharField(max_length=200)),
+                ("book", models.ForeignKey("otherapp.Book", models.CASCADE)),
+            ],
+            options={
+                "order_with_respect_to": "book",
+                "constraints": [
+                    models.CheckConstraint(
+                        check=models.Q(_order__gt=1), name="book_order_gt_1"
+                    ),
+                ],
+            },
+        )
+        changes = self.get_changes([], [self.book, after])
+        self.assertNumberMigrations(changes, "testapp", 1)
+        self.assertOperationTypes(
+            changes,
+            "testapp",
+            0,
+            ["CreateModel", "AddConstraint"],
+        )
+        self.assertOperationAttributes(
+            changes,
+            "testapp",
+            0,
+            0,
+            name="Author",
+            options={"order_with_respect_to": "book"},
+        )
+
+    def test_add_model_order_with_respect_to_index(self):
+        after = ModelState(
+            "testapp",
+            "Author",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                ("name", models.CharField(max_length=200)),
+                ("book", models.ForeignKey("otherapp.Book", models.CASCADE)),
+            ],
+            options={
+                "order_with_respect_to": "book",
+                "indexes": [models.Index(fields=["_order"], name="book_order_idx")],
+            },
+        )
+        changes = self.get_changes([], [self.book, after])
+        self.assertNumberMigrations(changes, "testapp", 1)
+        self.assertOperationTypes(changes, "testapp", 0, ["CreateModel"])
+        self.assertOperationAttributes(
+            changes,
+            "testapp",
+            0,
+            0,
+            name="Author",
+            options={
+                "order_with_respect_to": "book",
+                "indexes": [models.Index(fields=["_order"], name="book_order_idx")],
+            },
+        )
 
     def test_set_alter_order_with_respect_to_index_constraint_unique_together(self):
         tests = [
diff --git a/tests/migrations/test_optimizer.py b/tests/migrations/test_optimizer.py
index 2f6616ad5b..cb4000cb03 100644
--- a/tests/migrations/test_optimizer.py
+++ b/tests/migrations/test_optimizer.py
@@ -1172,3 +1172,181 @@ class OptimizerTests(SimpleTestCase):
             ],
             [],
         )
+
+    def test_create_model_add_index(self):
+        self.assertOptimizesTo(
+            [
+                migrations.CreateModel(
+                    name="Pony",
+                    fields=[
+                        ("weight", models.IntegerField()),
+                        ("age", models.IntegerField()),
+                    ],
+                    options={
+                        "indexes": [models.Index(fields=["age"], name="idx_pony_age")],
+                    },
+                ),
+                migrations.AddIndex(
+                    "Pony",
+                    models.Index(fields=["weight"], name="idx_pony_weight"),
+                ),
+            ],
+            [
+                migrations.CreateModel(
+                    name="Pony",
+                    fields=[
+                        ("weight", models.IntegerField()),
+                        ("age", models.IntegerField()),
+                    ],
+                    options={
+                        "indexes": [
+                            models.Index(fields=["age"], name="idx_pony_age"),
+                            models.Index(fields=["weight"], name="idx_pony_weight"),
+                        ],
+                    },
+                ),
+            ],
+        )
+
+    def test_create_model_remove_index(self):
+        self.assertOptimizesTo(
+            [
+                migrations.CreateModel(
+                    name="Pony",
+                    fields=[
+                        ("weight", models.IntegerField()),
+                        ("age", models.IntegerField()),
+                    ],
+                    options={
+                        "indexes": [
+                            models.Index(fields=["age"], name="idx_pony_age"),
+                            models.Index(fields=["weight"], name="idx_pony_weight"),
+                        ],
+                    },
+                ),
+                migrations.RemoveIndex("Pony", "idx_pony_age"),
+            ],
+            [
+                migrations.CreateModel(
+                    name="Pony",
+                    fields=[
+                        ("weight", models.IntegerField()),
+                        ("age", models.IntegerField()),
+                    ],
+                    options={
+                        "indexes": [
+                            models.Index(fields=["weight"], name="idx_pony_weight"),
+                        ],
+                    },
+                ),
+            ],
+        )
+
+    def test_create_model_remove_index_together_rename_index(self):
+        self.assertOptimizesTo(
+            [
+                migrations.CreateModel(
+                    name="Pony",
+                    fields=[
+                        ("weight", models.IntegerField()),
+                        ("age", models.IntegerField()),
+                    ],
+                    options={
+                        "index_together": [("age", "weight")],
+                    },
+                ),
+                migrations.RenameIndex(
+                    "Pony", new_name="idx_pony_age_weight", old_fields=("age", "weight")
+                ),
+            ],
+            [
+                migrations.CreateModel(
+                    name="Pony",
+                    fields=[
+                        ("weight", models.IntegerField()),
+                        ("age", models.IntegerField()),
+                    ],
+                    options={
+                        "indexes": [
+                            models.Index(
+                                fields=["age", "weight"], name="idx_pony_age_weight"
+                            ),
+                        ],
+                    },
+                ),
+            ],
+        )
+
+    def test_create_model_index_together_rename_index(self):
+        self.assertOptimizesTo(
+            [
+                migrations.CreateModel(
+                    name="Pony",
+                    fields=[
+                        ("weight", models.IntegerField()),
+                        ("age", models.IntegerField()),
+                        ("height", models.IntegerField()),
+                        ("rank", models.IntegerField()),
+                    ],
+                    options={
+                        "index_together": [("age", "weight"), ("height", "rank")],
+                    },
+                ),
+                migrations.RenameIndex(
+                    "Pony", new_name="idx_pony_age_weight", old_fields=("age", "weight")
+                ),
+            ],
+            [
+                migrations.CreateModel(
+                    name="Pony",
+                    fields=[
+                        ("weight", models.IntegerField()),
+                        ("age", models.IntegerField()),
+                        ("height", models.IntegerField()),
+                        ("rank", models.IntegerField()),
+                    ],
+                    options={
+                        "index_together": {("height", "rank")},
+                        "indexes": [
+                            models.Index(
+                                fields=["age", "weight"], name="idx_pony_age_weight"
+                            ),
+                        ],
+                    },
+                ),
+            ],
+        )
+
+    def test_create_model_rename_index_no_old_fields(self):
+        self.assertOptimizesTo(
+            [
+                migrations.CreateModel(
+                    name="Pony",
+                    fields=[
+                        ("weight", models.IntegerField()),
+                        ("age", models.IntegerField()),
+                    ],
+                    options={
+                        "indexes": [models.Index(fields=["age"], name="idx_pony_age")],
+                    },
+                ),
+                migrations.RenameIndex(
+                    "Pony", new_name="idx_pony_age_new", old_name="idx_pony_age"
+                ),
+            ],
+            [
+                migrations.CreateModel(
+                    name="Pony",
+                    fields=[
+                        ("weight", models.IntegerField()),
+                        ("age", models.IntegerField()),
+                    ],
+                    options={
+                        "indexes": [models.Index(fields=["age"], name="idx_pony_age")],
+                    },
+                ),
+                migrations.RenameIndex(
+                    "Pony", new_name="idx_pony_age_new", old_name="idx_pony_age"
+                ),
+            ],
+        )