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