370 lines
17 KiB
Python
370 lines
17 KiB
Python
from django.apps.registry import apps as global_apps
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from django.db import migrations, router
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from .exceptions import InvalidMigrationPlan
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from .loader import MigrationLoader
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from .recorder import MigrationRecorder
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from .state import ProjectState
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class MigrationExecutor:
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"""
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End-to-end migration execution - load migrations and run them up or down
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to a specified set of targets.
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"""
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def __init__(self, connection, progress_callback=None):
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self.connection = connection
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self.loader = MigrationLoader(self.connection)
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self.recorder = MigrationRecorder(self.connection)
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self.progress_callback = progress_callback
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def migration_plan(self, targets, clean_start=False):
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"""
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Given a set of targets, return a list of (Migration instance, backwards?).
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"""
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plan = []
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if clean_start:
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applied = set()
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else:
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applied = set(self.loader.applied_migrations)
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for target in targets:
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# If the target is (app_label, None), that means unmigrate everything
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if target[1] is None:
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for root in self.loader.graph.root_nodes():
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if root[0] == target[0]:
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for migration in self.loader.graph.backwards_plan(root):
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if migration in applied:
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plan.append((self.loader.graph.nodes[migration], True))
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applied.remove(migration)
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# If the migration is already applied, do backwards mode,
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# otherwise do forwards mode.
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elif target in applied:
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# Don't migrate backwards all the way to the target node (that
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# may roll back dependencies in other apps that don't need to
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# be rolled back); instead roll back through target's immediate
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# child(ren) in the same app, and no further.
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next_in_app = sorted(
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n for n in
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self.loader.graph.node_map[target].children
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if n[0] == target[0]
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)
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for node in next_in_app:
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for migration in self.loader.graph.backwards_plan(node):
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if migration in applied:
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plan.append((self.loader.graph.nodes[migration], True))
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applied.remove(migration)
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else:
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for migration in self.loader.graph.forwards_plan(target):
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if migration not in applied:
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plan.append((self.loader.graph.nodes[migration], False))
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applied.add(migration)
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return plan
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def _create_project_state(self, with_applied_migrations=False):
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"""
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Create a project state including all the applications without
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migrations and applied migrations if with_applied_migrations=True.
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"""
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state = ProjectState(real_apps=list(self.loader.unmigrated_apps))
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if with_applied_migrations:
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# Create the forwards plan Django would follow on an empty database
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full_plan = self.migration_plan(self.loader.graph.leaf_nodes(), clean_start=True)
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applied_migrations = {
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self.loader.graph.nodes[key] for key in self.loader.applied_migrations
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if key in self.loader.graph.nodes
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}
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for migration, _ in full_plan:
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if migration in applied_migrations:
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migration.mutate_state(state, preserve=False)
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return state
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def migrate(self, targets, plan=None, state=None, fake=False, fake_initial=False):
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"""
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Migrate the database up to the given targets.
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Django first needs to create all project states before a migration is
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(un)applied and in a second step run all the database operations.
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"""
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# The django_migrations table must be present to record applied
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# migrations.
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self.recorder.ensure_schema()
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if plan is None:
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plan = self.migration_plan(targets)
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# Create the forwards plan Django would follow on an empty database
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full_plan = self.migration_plan(self.loader.graph.leaf_nodes(), clean_start=True)
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all_forwards = all(not backwards for mig, backwards in plan)
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all_backwards = all(backwards for mig, backwards in plan)
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if not plan:
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if state is None:
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# The resulting state should include applied migrations.
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state = self._create_project_state(with_applied_migrations=True)
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elif all_forwards == all_backwards:
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# This should only happen if there's a mixed plan
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raise InvalidMigrationPlan(
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"Migration plans with both forwards and backwards migrations "
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"are not supported. Please split your migration process into "
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"separate plans of only forwards OR backwards migrations.",
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plan
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)
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elif all_forwards:
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if state is None:
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# The resulting state should still include applied migrations.
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state = self._create_project_state(with_applied_migrations=True)
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state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
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else:
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# No need to check for `elif all_backwards` here, as that condition
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# would always evaluate to true.
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state = self._migrate_all_backwards(plan, full_plan, fake=fake)
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self.check_replacements()
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return state
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def _migrate_all_forwards(self, state, plan, full_plan, fake, fake_initial):
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"""
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Take a list of 2-tuples of the form (migration instance, False) and
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apply them in the order they occur in the full_plan.
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"""
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migrations_to_run = {m[0] for m in plan}
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for migration, _ in full_plan:
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if not migrations_to_run:
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# We remove every migration that we applied from these sets so
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# that we can bail out once the last migration has been applied
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# and don't always run until the very end of the migration
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# process.
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break
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if migration in migrations_to_run:
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if 'apps' not in state.__dict__:
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if self.progress_callback:
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self.progress_callback("render_start")
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state.apps # Render all -- performance critical
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if self.progress_callback:
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self.progress_callback("render_success")
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state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
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migrations_to_run.remove(migration)
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return state
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def _migrate_all_backwards(self, plan, full_plan, fake):
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"""
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Take a list of 2-tuples of the form (migration instance, True) and
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unapply them in reverse order they occur in the full_plan.
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Since unapplying a migration requires the project state prior to that
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migration, Django will compute the migration states before each of them
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in a first run over the plan and then unapply them in a second run over
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the plan.
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"""
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migrations_to_run = {m[0] for m in plan}
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# Holds all migration states prior to the migrations being unapplied
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states = {}
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state = self._create_project_state()
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applied_migrations = {
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self.loader.graph.nodes[key] for key in self.loader.applied_migrations
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if key in self.loader.graph.nodes
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}
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if self.progress_callback:
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self.progress_callback("render_start")
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for migration, _ in full_plan:
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if not migrations_to_run:
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# We remove every migration that we applied from this set so
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# that we can bail out once the last migration has been applied
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# and don't always run until the very end of the migration
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# process.
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break
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if migration in migrations_to_run:
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if 'apps' not in state.__dict__:
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state.apps # Render all -- performance critical
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# The state before this migration
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states[migration] = state
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# The old state keeps as-is, we continue with the new state
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state = migration.mutate_state(state, preserve=True)
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migrations_to_run.remove(migration)
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elif migration in applied_migrations:
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# Only mutate the state if the migration is actually applied
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# to make sure the resulting state doesn't include changes
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# from unrelated migrations.
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migration.mutate_state(state, preserve=False)
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if self.progress_callback:
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self.progress_callback("render_success")
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for migration, _ in plan:
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self.unapply_migration(states[migration], migration, fake=fake)
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applied_migrations.remove(migration)
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# Generate the post migration state by starting from the state before
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# the last migration is unapplied and mutating it to include all the
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# remaining applied migrations.
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last_unapplied_migration = plan[-1][0]
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state = states[last_unapplied_migration]
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for index, (migration, _) in enumerate(full_plan):
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if migration == last_unapplied_migration:
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for migration, _ in full_plan[index:]:
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if migration in applied_migrations:
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migration.mutate_state(state, preserve=False)
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break
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return state
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def collect_sql(self, plan):
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"""
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Take a migration plan and return a list of collected SQL statements
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that represent the best-efforts version of that plan.
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"""
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statements = []
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state = None
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for migration, backwards in plan:
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with self.connection.schema_editor(collect_sql=True, atomic=migration.atomic) as schema_editor:
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if state is None:
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state = self.loader.project_state((migration.app_label, migration.name), at_end=False)
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if not backwards:
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state = migration.apply(state, schema_editor, collect_sql=True)
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else:
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state = migration.unapply(state, schema_editor, collect_sql=True)
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statements.extend(schema_editor.collected_sql)
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return statements
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def apply_migration(self, state, migration, fake=False, fake_initial=False):
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"""Run a migration forwards."""
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if self.progress_callback:
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self.progress_callback("apply_start", migration, fake)
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if not fake:
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if fake_initial:
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# Test to see if this is an already-applied initial migration
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applied, state = self.detect_soft_applied(state, migration)
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if applied:
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fake = True
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if not fake:
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# Alright, do it normally
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with self.connection.schema_editor(atomic=migration.atomic) as schema_editor:
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state = migration.apply(state, schema_editor)
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# For replacement migrations, record individual statuses
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if migration.replaces:
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for app_label, name in migration.replaces:
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self.recorder.record_applied(app_label, name)
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else:
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self.recorder.record_applied(migration.app_label, migration.name)
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# Report progress
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if self.progress_callback:
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self.progress_callback("apply_success", migration, fake)
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return state
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def unapply_migration(self, state, migration, fake=False):
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"""Run a migration backwards."""
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if self.progress_callback:
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self.progress_callback("unapply_start", migration, fake)
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if not fake:
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with self.connection.schema_editor(atomic=migration.atomic) as schema_editor:
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state = migration.unapply(state, schema_editor)
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# For replacement migrations, record individual statuses
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if migration.replaces:
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for app_label, name in migration.replaces:
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self.recorder.record_unapplied(app_label, name)
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else:
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self.recorder.record_unapplied(migration.app_label, migration.name)
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# Report progress
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if self.progress_callback:
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self.progress_callback("unapply_success", migration, fake)
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return state
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def check_replacements(self):
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"""
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Mark replacement migrations applied if their replaced set all are.
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Do this unconditionally on every migrate, rather than just when
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migrations are applied or unapplied, to correctly handle the case
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when a new squash migration is pushed to a deployment that already had
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all its replaced migrations applied. In this case no new migration will
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be applied, but the applied state of the squashed migration must be
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maintained.
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"""
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applied = self.recorder.applied_migrations()
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for key, migration in self.loader.replacements.items():
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all_applied = all(m in applied for m in migration.replaces)
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if all_applied and key not in applied:
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self.recorder.record_applied(*key)
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def detect_soft_applied(self, project_state, migration):
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"""
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Test whether a migration has been implicitly applied - that the
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tables or columns it would create exist. This is intended only for use
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on initial migrations (as it only looks for CreateModel and AddField).
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"""
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def should_skip_detecting_model(migration, model):
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"""
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No need to detect tables for proxy models, unmanaged models, or
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models that can't be migrated on the current database.
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"""
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return (
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model._meta.proxy or not model._meta.managed or not
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router.allow_migrate(
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self.connection.alias, migration.app_label,
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model_name=model._meta.model_name,
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)
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)
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if migration.initial is None:
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# Bail if the migration isn't the first one in its app
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if any(app == migration.app_label for app, name in migration.dependencies):
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return False, project_state
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elif migration.initial is False:
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# Bail if it's NOT an initial migration
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return False, project_state
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if project_state is None:
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after_state = self.loader.project_state((migration.app_label, migration.name), at_end=True)
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else:
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after_state = migration.mutate_state(project_state)
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apps = after_state.apps
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found_create_model_migration = False
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found_add_field_migration = False
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with self.connection.cursor() as cursor:
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existing_table_names = self.connection.introspection.table_names(cursor)
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# Make sure all create model and add field operations are done
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for operation in migration.operations:
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if isinstance(operation, migrations.CreateModel):
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model = apps.get_model(migration.app_label, operation.name)
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if model._meta.swapped:
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# We have to fetch the model to test with from the
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# main app cache, as it's not a direct dependency.
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model = global_apps.get_model(model._meta.swapped)
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if should_skip_detecting_model(migration, model):
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continue
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if model._meta.db_table not in existing_table_names:
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return False, project_state
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found_create_model_migration = True
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elif isinstance(operation, migrations.AddField):
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model = apps.get_model(migration.app_label, operation.model_name)
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if model._meta.swapped:
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# We have to fetch the model to test with from the
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# main app cache, as it's not a direct dependency.
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model = global_apps.get_model(model._meta.swapped)
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if should_skip_detecting_model(migration, model):
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continue
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table = model._meta.db_table
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field = model._meta.get_field(operation.name)
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# Handle implicit many-to-many tables created by AddField.
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if field.many_to_many:
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if field.remote_field.through._meta.db_table not in existing_table_names:
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return False, project_state
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else:
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found_add_field_migration = True
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continue
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column_names = [
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column.name for column in
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self.connection.introspection.get_table_description(self.connection.cursor(), table)
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]
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if field.column not in column_names:
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return False, project_state
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found_add_field_migration = True
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# If we get this far and we found at least one CreateModel or AddField migration,
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# the migration is considered implicitly applied.
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return (found_create_model_migration or found_add_field_migration), after_state
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