from __future__ import unicode_literals from django.db import migrations from .loader import MigrationLoader from .recorder import MigrationRecorder class MigrationExecutor(object): """ End-to-end migration execution - loads migrations, and runs them up or down to a specified set of targets. """ def __init__(self, connection, progress_callback=None): self.connection = connection self.loader = MigrationLoader(self.connection) self.recorder = MigrationRecorder(self.connection) self.progress_callback = progress_callback def migration_plan(self, targets): """ Given a set of targets, returns a list of (Migration instance, backwards?). """ plan = [] applied = set(self.loader.applied_migrations) for target in targets: # If the target is (app_label, None), that means unmigrate everything if target[1] is None: for root in self.loader.graph.root_nodes(): if root[0] == target[0]: for migration in self.loader.graph.backwards_plan(root): if migration in applied: plan.append((self.loader.graph.nodes[migration], True)) applied.remove(migration) # If the migration is already applied, do backwards mode, # otherwise do forwards mode. elif target in applied: backwards_plan = self.loader.graph.backwards_plan(target)[:-1] # We only do this if the migration is not the most recent one # in its app - that is, another migration with the same app # label is in the backwards plan if any(node[0] == target[0] for node in backwards_plan): for migration in backwards_plan: if migration in applied: plan.append((self.loader.graph.nodes[migration], True)) applied.remove(migration) else: for migration in self.loader.graph.forwards_plan(target): if migration not in applied: plan.append((self.loader.graph.nodes[migration], False)) applied.add(migration) return plan def migrate(self, targets, plan=None, fake=False): """ Migrates the database up to the given targets. """ if plan is None: plan = self.migration_plan(targets) for migration, backwards in plan: if not backwards: self.apply_migration(migration, fake=fake) else: self.unapply_migration(migration, fake=fake) def collect_sql(self, plan): """ Takes a migration plan and returns a list of collected SQL statements that represent the best-efforts version of that plan. """ statements = [] for migration, backwards in plan: with self.connection.schema_editor(collect_sql=True) as schema_editor: project_state = self.loader.project_state((migration.app_label, migration.name), at_end=False) if not backwards: migration.apply(project_state, schema_editor, collect_sql=True) else: migration.unapply(project_state, schema_editor, collect_sql=True) statements.extend(schema_editor.collected_sql) return statements def apply_migration(self, migration, fake=False): """ Runs a migration forwards. """ if self.progress_callback: self.progress_callback("apply_start", migration, fake) if not fake: # Test to see if this is an already-applied initial migration if self.detect_soft_applied(migration): fake = True else: # Alright, do it normally with self.connection.schema_editor() as schema_editor: project_state = self.loader.project_state((migration.app_label, migration.name), at_end=False) migration.apply(project_state, schema_editor) # For replacement migrations, record individual statuses if migration.replaces: for app_label, name in migration.replaces: self.recorder.record_applied(app_label, name) else: self.recorder.record_applied(migration.app_label, migration.name) # Report progress if self.progress_callback: self.progress_callback("apply_success", migration, fake) def unapply_migration(self, migration, fake=False): """ Runs a migration backwards. """ if self.progress_callback: self.progress_callback("unapply_start", migration, fake) if not fake: with self.connection.schema_editor() as schema_editor: project_state = self.loader.project_state((migration.app_label, migration.name), at_end=False) migration.unapply(project_state, schema_editor) # For replacement migrations, record individual statuses if migration.replaces: for app_label, name in migration.replaces: self.recorder.record_unapplied(app_label, name) else: self.recorder.record_unapplied(migration.app_label, migration.name) # Report progress if self.progress_callback: self.progress_callback("unapply_success", migration, fake) def detect_soft_applied(self, migration): """ Tests whether a migration has been implicitly applied - that the tables it would create exist. This is intended only for use on initial migrations (as it only looks for CreateModel). """ project_state = self.loader.project_state((migration.app_label, migration.name), at_end=True) apps = project_state.render() found_create_migration = False for operation in migration.operations: if isinstance(operation, migrations.CreateModel): model = apps.get_model(migration.app_label, operation.name) if model._meta.db_table not in self.connection.introspection.get_table_list(self.connection.cursor()): return False found_create_migration = True # If we get this far and we found at least one CreateModel migration, # the migration is considered implicitly applied. return found_create_migration