django1/django/db/migrations/executor.py

65 lines
2.5 KiB
Python

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):
self.connection = connection
self.loader = MigrationLoader(self.connection)
self.recorder = MigrationRecorder(self.connection)
def migration_plan(self, targets):
"""
Given a set of targets, returns a list of (Migration instance, backwards?).
"""
plan = []
applied = self.recorder.applied_migrations()
for target in targets:
# If the migration is already applied, do backwards mode,
# otherwise do forwards mode.
if target in applied:
for migration in self.loader.graph.backwards_plan(target)[:-1]:
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):
"""
Migrates the database up to the given targets.
"""
plan = self.migration_plan(targets)
for migration, backwards in plan:
if not backwards:
self.apply_migration(migration)
else:
self.unapply_migration(migration)
def apply_migration(self, migration):
"""
Runs a migration forwards.
"""
with self.connection.schema_editor() as schema_editor:
project_state = self.loader.graph.project_state((migration.app_label, migration.name), at_end=False)
migration.apply(project_state, schema_editor)
self.recorder.record_applied(migration.app_label, migration.name)
def unapply_migration(self, migration):
"""
Runs a migration backwards.
"""
with self.connection.schema_editor() as schema_editor:
project_state = self.loader.graph.project_state((migration.app_label, migration.name), at_end=False)
migration.unapply(project_state, schema_editor)
self.recorder.record_unapplied(migration.app_label, migration.name)