Fixed #24110 -- Rewrote migration unapply to preserve intermediate states
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Markus Holtermann
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d89019a84d
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fdc2cc9487
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@ -115,28 +115,39 @@ class Migration(object):
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Takes a project_state representing all migrations prior to this one
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and a schema_editor for a live database and applies the migration
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in a reverse order.
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The backwards migration process consists of two phases:
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1. The intermediate states from right before the first until right
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after the last opertion inside this migration are preserved.
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2. The operations are applied in reverse order using the states
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recorded in step 1.
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"""
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# We need to pre-calculate the stack of project states
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# Construct all the intermediate states we need for a reverse migration
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to_run = []
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new_state = project_state
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# Phase 1
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for operation in self.operations:
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# If this operation cannot be represented as SQL, place a comment
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# there instead
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if collect_sql and not operation.reduces_to_sql:
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schema_editor.collected_sql.append("--")
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schema_editor.collected_sql.append("-- MIGRATION NOW PERFORMS OPERATION THAT CANNOT BE "
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"WRITTEN AS SQL:")
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schema_editor.collected_sql.append("-- %s" % operation.describe())
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schema_editor.collected_sql.append("--")
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continue
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# If it's irreversible, error out
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if not operation.reversible:
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raise Migration.IrreversibleError("Operation %s in %s is not reversible" % (operation, self))
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old_state = project_state.clone()
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operation.state_forwards(self.app_label, project_state)
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to_run.append((operation, old_state, project_state))
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# Now run them in reverse
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to_run.reverse()
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# Preserve new state from previous run to not tamper the same state
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# over all operations
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new_state = new_state.clone()
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old_state = new_state.clone()
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operation.state_forwards(self.app_label, new_state)
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to_run.insert(0, (operation, old_state, new_state))
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# Phase 2
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for operation, to_state, from_state in to_run:
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if collect_sql:
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if not operation.reduces_to_sql:
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schema_editor.collected_sql.append("--")
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schema_editor.collected_sql.append("-- MIGRATION NOW PERFORMS OPERATION THAT CANNOT BE "
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"WRITTEN AS SQL:")
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schema_editor.collected_sql.append("-- %s" % operation.describe())
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schema_editor.collected_sql.append("--")
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continue
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if not schema_editor.connection.features.can_rollback_ddl and operation.atomic:
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# We're forcing a transaction on a non-transactional-DDL backend
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with atomic(schema_editor.connection.alias):
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@ -26,3 +26,5 @@ Bugfixes
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(:ticket:`24097`).
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* Added correct formats for Greek (``el``) (:ticket:`23967`).
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* Fixed a migration crash when unapplying a migration (:ticket:`24110`).
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@ -465,27 +465,33 @@ class OperationTests(OperationTestBase):
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# Test the state alteration
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operation = migrations.RenameModel("Pony", "Horse")
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self.assertEqual(operation.describe(), "Rename model Pony to Horse")
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new_state = project_state.clone()
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operation.state_forwards("test_rnmo", new_state)
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self.assertNotIn(("test_rnmo", "pony"), new_state.models)
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self.assertIn(("test_rnmo", "horse"), new_state.models)
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# Remember, RenameModel also repoints all incoming FKs and M2Ms
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self.assertEqual("test_rnmo.Horse", new_state.models["test_rnmo", "rider"].fields[1][1].rel.to)
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# Test the database alteration
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# Test initial state and database
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self.assertIn(("test_rnmo", "pony"), project_state.models)
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self.assertNotIn(("test_rnmo", "horse"), project_state.models)
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self.assertTableExists("test_rnmo_pony")
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self.assertTableNotExists("test_rnmo_horse")
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if connection.features.supports_foreign_keys:
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self.assertFKExists("test_rnmo_rider", ["pony_id"], ("test_rnmo_pony", "id"))
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self.assertFKNotExists("test_rnmo_rider", ["pony_id"], ("test_rnmo_horse", "id"))
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with connection.schema_editor() as editor:
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operation.database_forwards("test_rnmo", editor, project_state, new_state)
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# Migrate forwards
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new_state = project_state.clone()
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new_state = self.apply_operations("test_rnmo", new_state, [operation])
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# Test new state and database
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self.assertNotIn(("test_rnmo", "pony"), new_state.models)
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self.assertIn(("test_rnmo", "horse"), new_state.models)
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# RenameModel also repoints all incoming FKs and M2Ms
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self.assertEqual("test_rnmo.Horse", new_state.models["test_rnmo", "rider"].fields[1][1].rel.to)
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self.assertTableNotExists("test_rnmo_pony")
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self.assertTableExists("test_rnmo_horse")
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if connection.features.supports_foreign_keys:
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self.assertFKNotExists("test_rnmo_rider", ["pony_id"], ("test_rnmo_pony", "id"))
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self.assertFKExists("test_rnmo_rider", ["pony_id"], ("test_rnmo_horse", "id"))
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# And test reversal
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self.unapply_operations("test_rnmo", project_state, [operation])
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# Migrate backwards
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original_state = self.unapply_operations("test_rnmo", project_state, [operation])
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# Test original state and database
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self.assertIn(("test_rnmo", "pony"), original_state.models)
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self.assertNotIn(("test_rnmo", "horse"), original_state.models)
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self.assertEqual("Pony", original_state.models["test_rnmo", "rider"].fields[1][1].rel.to)
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self.assertTableExists("test_rnmo_pony")
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self.assertTableNotExists("test_rnmo_horse")
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if connection.features.supports_foreign_keys:
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