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from __future__ import unicode_literals
from django.db import migrations
from django.apps.registry import apps as global_apps
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:
# Don't migrate backwards all the way to the target node (that
# may roll back dependencies in other apps that don't need to
# be rolled back); instead roll back through target's immediate
# child(ren) in the same app, and no further.
next_in_app = sorted(
n for n in
self.loader.graph.dependents.get(target, set())
if n[0] == target[0]
)
for node in next_in_app:
for migration in self.loader.graph.backwards_plan(node):
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
# Bail if the migration isn't the first one in its app
if [name for app, name in migration.dependencies if app == migration.app_label]:
return False
# Make sure all create model are done
for operation in migration.operations:
if isinstance(operation, migrations.CreateModel):
model = apps.get_model(migration.app_label, operation.name)
if model._meta.swapped:
# We have to fetch the model to test with from the
# main app cache, as it's not a direct dependency.
model = global_apps.get_model(model._meta.swapped)
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
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