import re import datetime from django.db.migrations import operations from django.db.migrations.migration import Migration from django.db.migrations.questioner import MigrationQuestioner class MigrationAutodetector(object): """ Takes a pair of ProjectStates, and compares them to see what the first would need doing to make it match the second (the second usually being the project's current state). Note that this naturally operates on entire projects at a time, as it's likely that changes interact (for example, you can't add a ForeignKey without having a migration to add the table it depends on first). A user interface may offer single-app usage if it wishes, with the caveat that it may not always be possible. """ def __init__(self, from_state, to_state, questioner=None): self.from_state = from_state self.to_state = to_state self.questioner = questioner or MigrationQuestioner() def changes(self, graph, trim_to_apps=None): """ Main entry point to produce a list of appliable changes. Takes a graph to base names on and an optional set of apps to try and restrict to (restriction is not guaranteed) """ changes = self._detect_changes() changes = self._arrange_for_graph(changes, graph) if trim_to_apps: changes = self._trim_to_apps(changes, trim_to_apps) return changes def _detect_changes(self): """ Returns a dict of migration plans which will achieve the change from from_state to to_state. The dict has app labels as keys and a list of migrations as values. The resulting migrations aren't specially named, but the names do matter for dependencies inside the set. """ # We'll store migrations as lists by app names for now self.migrations = {} old_apps = self.from_state.render() new_apps = self.to_state.render() # Prepare lists of old/new model keys that we care about # (i.e. ignoring proxy ones) old_model_keys = [ (al, mn) for al, mn in self.from_state.models.keys() if not old_apps.get_model(al, mn)._meta.proxy ] new_model_keys = [ (al, mn) for al, mn in self.to_state.models.keys() if not new_apps.get_model(al, mn)._meta.proxy ] # Adding models. Phase 1 is adding models with no outward relationships. added_models = set(new_model_keys) - set(old_model_keys) pending_add = {} for app_label, model_name in added_models: model_state = self.to_state.models[app_label, model_name] # Are there any relationships out from this model? if so, punt it to the next phase. related_fields = [] for field in new_apps.get_model(app_label, model_name)._meta.local_fields: if field.rel: if field.rel.to: related_fields.append((field.name, field.rel.to._meta.app_label, field.rel.to._meta.model_name)) if hasattr(field.rel, "through") and not field.rel.though._meta.auto_created: related_fields.append((field.name, field.rel.through._meta.app_label, field.rel.through._meta.model_name)) if related_fields: pending_add[app_label, model_name] = related_fields else: self.add_to_migration( app_label, operations.CreateModel( name=model_state.name, fields=model_state.fields, options=model_state.options, bases=model_state.bases, ) ) # Phase 2 is progressively adding pending models, splitting up into two # migrations if required. pending_new_fks = [] while pending_add: # Is there one we can add that has all dependencies satisfied? satisfied = [(m, rf) for m, rf in pending_add.items() if all((al, mn) not in pending_add for f, al, mn in rf)] if satisfied: (app_label, model_name), related_fields = sorted(satisfied)[0] model_state = self.to_state.models[app_label, model_name] self.add_to_migration( app_label, operations.CreateModel( name=model_state.name, fields=model_state.fields, options=model_state.options, bases=model_state.bases, ) ) for field_name, other_app_label, other_model_name in related_fields: # If it depends on a swappable something, add a dynamic depend'cy swappable_setting = new_apps.get_model(app_label, model_name)._meta.get_field_by_name(field_name)[0].swappable_setting if swappable_setting is not None: self.add_swappable_dependency(app_label, swappable_setting) elif app_label != other_app_label: self.add_dependency(app_label, other_app_label) del pending_add[app_label, model_name] # Ah well, we'll need to split one. Pick deterministically. else: (app_label, model_name), related_fields = sorted(pending_add.items())[0] model_state = self.to_state.models[app_label, model_name] # Work out the fields that need splitting out bad_fields = dict((f, (al, mn)) for f, al, mn in related_fields if (al, mn) in pending_add) # Create the model, without those self.add_to_migration( app_label, operations.CreateModel( name=model_state.name, fields=[(n, f) for n, f in model_state.fields if n not in bad_fields], options=model_state.options, bases=model_state.bases, ) ) # Add the bad fields to be made in a phase 3 for field_name, (other_app_label, other_model_name) in bad_fields.items(): pending_new_fks.append((app_label, model_name, field_name, other_app_label)) del pending_add[app_label, model_name] # Phase 3 is adding the final set of FKs as separate new migrations for app_label, model_name, field_name, other_app_label in pending_new_fks: model_state = self.to_state.models[app_label, model_name] self.add_to_migration( app_label, operations.AddField( model_name=model_name, name=field_name, field=model_state.get_field_by_name(field_name), ), new=True, ) # If it depends on a swappable something, add a dynamic depend'cy swappable_setting = new_apps.get_model(app_label, model_name)._meta.get_field_by_name(field_name)[0].swappable_setting if swappable_setting is not None: self.add_swappable_dependency(app_label, swappable_setting) elif app_label != other_app_label: self.add_dependency(app_label, other_app_label) # Removing models removed_models = set(old_model_keys) - set(new_model_keys) for app_label, model_name in removed_models: model_state = self.from_state.models[app_label, model_name] self.add_to_migration( app_label, operations.DeleteModel( model_state.name, ) ) # Changes within models kept_models = set(old_model_keys).intersection(new_model_keys) old_fields = set() new_fields = set() for app_label, model_name in kept_models: old_model_state = self.from_state.models[app_label, model_name] new_model_state = self.to_state.models[app_label, model_name] # Collect field changes for later global dealing with (so AddFields # always come before AlterFields even on separate models) old_fields.update((app_label, model_name, x) for x, y in old_model_state.fields) new_fields.update((app_label, model_name, x) for x, y in new_model_state.fields) # Unique_together changes if old_model_state.options.get("unique_together", set()) != new_model_state.options.get("unique_together", set()): self.add_to_migration( app_label, operations.AlterUniqueTogether( name=model_name, unique_together=new_model_state.options.get("unique_together", set()), ) ) # New fields for app_label, model_name, field_name in new_fields - old_fields: old_model_state = self.from_state.models[app_label, model_name] new_model_state = self.to_state.models[app_label, model_name] field = new_model_state.get_field_by_name(field_name) # Scan to see if this is actually a rename! field_dec = field.deconstruct()[1:] found_rename = False for rem_app_label, rem_model_name, rem_field_name in (old_fields - new_fields): if rem_app_label == app_label and rem_model_name == model_name: if old_model_state.get_field_by_name(rem_field_name).deconstruct()[1:] == field_dec: if self.questioner.ask_rename(model_name, rem_field_name, field_name, field): self.add_to_migration( app_label, operations.RenameField( model_name=model_name, old_name=rem_field_name, new_name=field_name, ) ) old_fields.remove((rem_app_label, rem_model_name, rem_field_name)) new_fields.remove((app_label, model_name, field_name)) found_rename = True break if found_rename: continue # You can't just add NOT NULL fields with no default if not field.null and not field.has_default(): field = field.clone() field.default = self.questioner.ask_not_null_addition(field_name, model_name) self.add_to_migration( app_label, operations.AddField( model_name=model_name, name=field_name, field=field, preserve_default=False, ) ) else: self.add_to_migration( app_label, operations.AddField( model_name=model_name, name=field_name, field=field, ) ) # Old fields for app_label, model_name, field_name in old_fields - new_fields: old_model_state = self.from_state.models[app_label, model_name] new_model_state = self.to_state.models[app_label, model_name] self.add_to_migration( app_label, operations.RemoveField( model_name=model_name, name=field_name, ) ) # The same fields for app_label, model_name, field_name in old_fields.intersection(new_fields): # Did the field change? old_model_state = self.from_state.models[app_label, model_name] new_model_state = self.to_state.models[app_label, model_name] old_field_dec = old_model_state.get_field_by_name(field_name).deconstruct() new_field_dec = new_model_state.get_field_by_name(field_name).deconstruct() if old_field_dec != new_field_dec: self.add_to_migration( app_label, operations.AlterField( model_name=model_name, name=field_name, field=new_model_state.get_field_by_name(field_name), ) ) # Alright, now add internal dependencies for app_label, migrations in self.migrations.items(): for m1, m2 in zip(migrations, migrations[1:]): m2.dependencies.append((app_label, m1.name)) # Clean up dependencies for app_label, migrations in self.migrations.items(): for migration in migrations: migration.dependencies = list(set(migration.dependencies)) return self.migrations def add_to_migration(self, app_label, operation, new=False): migrations = self.migrations.setdefault(app_label, []) if not migrations or new: subclass = type("Migration", (Migration,), {"operations": [], "dependencies": []}) instance = subclass("auto_%i" % (len(migrations) + 1), app_label) migrations.append(instance) migrations[-1].operations.append(operation) def add_dependency(self, app_label, other_app_label): """ Adds a dependency to app_label's newest migration on other_app_label's latest migration. """ if self.migrations.get(other_app_label, []): dependency = (other_app_label, self.migrations[other_app_label][-1].name) else: dependency = (other_app_label, "__first__") self.migrations[app_label][-1].dependencies.append(dependency) def add_swappable_dependency(self, app_label, setting_name): """ Adds a dependency to the value of a swappable model setting. """ dependency = ("__setting__", setting_name) self.migrations[app_label][-1].dependencies.append(dependency) def _arrange_for_graph(self, changes, graph): """ Takes in a result from changes() and a MigrationGraph, and fixes the names and dependencies of the changes so they extend the graph from the leaf nodes for each app. """ leaves = graph.leaf_nodes() name_map = {} for app_label, migrations in list(changes.items()): if not migrations: continue # Find the app label's current leaf node app_leaf = None for leaf in leaves: if leaf[0] == app_label: app_leaf = leaf break # Do they want an initial migration for this app? if app_leaf is None and not self.questioner.ask_initial(app_label): # They don't. for migration in migrations: name_map[(app_label, migration.name)] = (app_label, "__first__") del changes[app_label] continue # Work out the next number in the sequence if app_leaf is None: next_number = 1 else: next_number = (self.parse_number(app_leaf[1]) or 0) + 1 # Name each migration for i, migration in enumerate(migrations): if i == 0 and app_leaf: migration.dependencies.append(app_leaf) if i == 0 and not app_leaf: new_name = "0001_initial" else: new_name = "%04i_%s" % (next_number, self.suggest_name(migration.operations)) name_map[(app_label, migration.name)] = (app_label, new_name) migration.name = new_name # Now fix dependencies for app_label, migrations in changes.items(): for migration in migrations: migration.dependencies = [name_map.get(d, d) for d in migration.dependencies] return changes def _trim_to_apps(self, changes, app_labels): """ Takes changes from arrange_for_graph and set of app labels and returns a modified set of changes which trims out as many migrations that are not in app_labels as possible. Note that some other migrations may still be present, as they may be required dependencies. """ # Gather other app dependencies in a first pass app_dependencies = {} for app_label, migrations in changes.items(): for migration in migrations: for dep_app_label, name in migration.dependencies: app_dependencies.setdefault(app_label, set()).add(dep_app_label) required_apps = set(app_labels) # Keep resolving till there's no change old_required_apps = None while old_required_apps != required_apps: old_required_apps = set(required_apps) for app_label in list(required_apps): required_apps.update(app_dependencies.get(app_label, set())) # Remove all migrations that aren't needed for app_label in list(changes.keys()): if app_label not in required_apps: del changes[app_label] return changes @classmethod def suggest_name(cls, ops): """ Given a set of operations, suggests a name for the migration they might represent. Names are not guaranteed to be unique, but we put some effort in to the fallback name to avoid VCS conflicts if we can. """ if len(ops) == 1: if isinstance(ops[0], operations.CreateModel): return ops[0].name.lower() elif isinstance(ops[0], operations.DeleteModel): 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()) elif isinstance(ops[0], operations.RemoveField): return "remove_%s_%s" % (ops[0].model_name.lower(), ops[0].name.lower()) elif all(isinstance(o, operations.CreateModel) 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 def parse_number(cls, name): """ Given a migration name, tries to extract a number from the beginning of it. If no number found, returns None. """ if re.match(r"^\d+_", name): return int(name.split("_")[0]) return None