Fixed #31825 -- Made RenameField operation a noop for fields with db_column.

AUTHORS

@@ -386,6 +386,7 @@ answer newbie questions, and generally made Django that much better:
     Ilya Semenov <semenov@inetss.com>
     Ingo Klöcker <djangoproject@ingo-kloecker.de>
     I.S. van Oostveen <v.oostveen@idca.nl>
+    Iuri de Silvio <https://github.com/iurisilvio>
     ivan.chelubeev@gmail.com
     Ivan Sagalaev (Maniac) <http://www.softwaremaniacs.org/>
     Jaap Roes <jaap.roes@gmail.com>

django/db/backends/base/schema.py

@@ -538,6 +538,8 @@ class BaseDatabaseSchemaEditor:
         If `strict` is True, raise errors if the old column does not match
         `old_field` precisely.
         """
+        if not self._field_should_be_altered(old_field, new_field):
+            return
         # Ensure this field is even column-based
         old_db_params = old_field.db_parameters(connection=self.connection)
         old_type = old_db_params['type']
@@ -1034,6 +1036,13 @@ class BaseDatabaseSchemaEditor:
             output.append(self._create_index_sql(model, [field]))
         return output
 
+    def _field_should_be_altered(self, old_field, new_field):
+        # Don't alter when changing only a field name.
+        return (
+            old_field.column != new_field.column or
+            old_field.deconstruct()[1:] != new_field.deconstruct()[1:]
+        )
+
     def _field_should_be_indexed(self, model, field):
         return field.db_index and not field.unique
 

django/db/backends/sqlite3/schema.py

@@ -99,6 +99,8 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
             super().alter_db_table(model, old_db_table, new_db_table)
 
     def alter_field(self, model, old_field, new_field, strict=False):
+        if not self._field_should_be_altered(old_field, new_field):
+            return
         old_field_name = old_field.name
         table_name = model._meta.db_table
         _, old_column_name = old_field.get_attname_column()

tests/migrations/test_operations.py

@@ -1632,6 +1632,48 @@ class OperationTests(OperationTestBase):
         self.assertEqual(definition[1], [])
         self.assertEqual(definition[2], {'model_name': "Pony", 'old_name': "pink", 'new_name': "blue"})
 
+    def test_rename_field_with_db_column(self):
+        project_state = self.apply_operations('test_rfwdbc', ProjectState(), operations=[
+            migrations.CreateModel('Pony', fields=[
+                ('id', models.AutoField(primary_key=True)),
+                ('field', models.IntegerField(db_column='db_field')),
+                ('fk_field', models.ForeignKey(
+                    'Pony',
+                    models.CASCADE,
+                    db_column='db_fk_field',
+                )),
+            ]),
+        ])
+        new_state = project_state.clone()
+        operation = migrations.RenameField('Pony', 'field', 'renamed_field')
+        operation.state_forwards('test_rfwdbc', new_state)
+        self.assertIn('renamed_field', new_state.models['test_rfwdbc', 'pony'].fields)
+        self.assertNotIn('field', new_state.models['test_rfwdbc', 'pony'].fields)
+        self.assertColumnExists('test_rfwdbc_pony', 'db_field')
+        with connection.schema_editor() as editor:
+            with self.assertNumQueries(0):
+                operation.database_forwards('test_rfwdbc', editor, project_state, new_state)
+        self.assertColumnExists('test_rfwdbc_pony', 'db_field')
+        with connection.schema_editor() as editor:
+            with self.assertNumQueries(0):
+                operation.database_backwards('test_rfwdbc', editor, new_state, project_state)
+        self.assertColumnExists('test_rfwdbc_pony', 'db_field')
+
+        new_state = project_state.clone()
+        operation = migrations.RenameField('Pony', 'fk_field', 'renamed_fk_field')
+        operation.state_forwards('test_rfwdbc', new_state)
+        self.assertIn('renamed_fk_field', new_state.models['test_rfwdbc', 'pony'].fields)
+        self.assertNotIn('fk_field', new_state.models['test_rfwdbc', 'pony'].fields)
+        self.assertColumnExists('test_rfwdbc_pony', 'db_fk_field')
+        with connection.schema_editor() as editor:
+            with self.assertNumQueries(0):
+                operation.database_forwards('test_rfwdbc', editor, project_state, new_state)
+        self.assertColumnExists('test_rfwdbc_pony', 'db_fk_field')
+        with connection.schema_editor() as editor:
+            with self.assertNumQueries(0):
+                operation.database_backwards('test_rfwdbc', editor, new_state, project_state)
+        self.assertColumnExists('test_rfwdbc_pony', 'db_fk_field')
+
     def test_rename_missing_field(self):
         state = ProjectState()
         state.add_model(ModelState('app', 'model', []))