1. Luke Plant
  2. south

Source

south / south / migration / __init__.py

The rebase branch has multiple heads

"""
Main migration logic.
"""

import sys

from django.core.exceptions import ImproperlyConfigured

import south.db
from south import exceptions
from south.models import MigrationHistory
from south.db import db, DEFAULT_DB_ALIAS
from south.migration.migrators import (Backwards, Forwards,
                                       DryRunMigrator, FakeMigrator,
                                       LoadInitialDataMigrator)
from south.migration.base import Migration, Migrations
from south.migration.utils import SortedSet
from south.migration.base import all_migrations
from south.signals import pre_migrate, post_migrate


def to_apply(forwards, done):
    return [m for m in forwards if m not in done]

def to_unapply(backwards, done):
    return [m for m in backwards if (m in done) or m.is_rebase()]

def problems(pending, done):
    last = None
    if not pending:
        raise StopIteration()
    for migration in pending:
        if migration in done:
            last = migration
            continue
        if last and migration not in done:
            yield last, migration

def forwards_problems(pending, done, verbosity):
    """
    Takes the list of linearised pending migrations, and the set of done ones,
    and returns the list of problems, if any.
    """
    return inner_problem_check(problems(reversed(pending), done), done, verbosity)

def backwards_problems(pending, done, verbosity):
    return inner_problem_check(problems(pending, done), done, verbosity)

def inner_problem_check(problems, done, verbosity):
    "Takes a set of possible problems and gets the actual issues out of it."
    result = []
    for last, migration in problems:
        # 'Last' is the last applied migration. Step back from it until we
        # either find nothing wrong, or we find something.
        to_check = list(last.dependencies)
        while to_check:
            checking = to_check.pop()
            if checking not in done:
                # That's bad. Error.
                if verbosity:
                    print (" ! Migration %s should not have been applied "
                           "before %s but was." % (last, checking))
                result.append((last, checking))
            else:
                to_check.extend(checking.dependencies)
    return result

def check_migration_histories(histories, delete_ghosts=False, ignore_ghosts=False):
    "Checks that there's no 'ghost' migrations in the database."
    exists = SortedSet()
    ghosts = []
    for h in histories:
        try:
            m = h.get_migration()
            m.migration()
        except exceptions.UnknownMigration:
            ghosts.append(h)
        except ImproperlyConfigured:
            pass                        # Ignore missing applications
        else:
            exists.add(m)
    if ghosts:
        # They may want us to delete ghosts.
        if delete_ghosts:
            for h in ghosts:
                h.delete()
        elif not ignore_ghosts:
            raise exceptions.GhostMigrations(ghosts)
    return exists

def get_dependencies(target, migrations):
    forwards = lambda allow_rebase=False: list()
    backwards = lambda allow_rebase=False: list()
    if target is None:
        backwards = migrations[0].backwards_plan
    else:
        forwards = target.forwards_plan
        # When migrating backwards we want to remove up to and
        # including the next migration up in this app (not the next
        # one, that includes other apps)
        migration_before_here = target.next()
        if migration_before_here:
            backwards = migration_before_here.backwards_plan
    return forwards, backwards

def get_direction(target, applied, migrations, verbosity, interactive):
    # Get the forwards and reverse dependencies for this target
    forwards, backwards = get_dependencies(target, migrations)
    # Is the whole forward branch applied?
    problems = None
    if target is not None:
        forwards = forwards(allow_rebase = not [x for x in applied if x.migrations is target.migrations])
        workplan = to_apply(forwards, applied)
    else:
        workplan = None
    # See if there's some forward work to be done.
    if not workplan:
        # If they're all applied, we only know it's not backwards
        direction = None
    else:
        # If the remaining migrations are strictly a right segment of
        # the forwards trace, we just need to go forwards to our
        # target (and check for badness)
        problems = forwards_problems(forwards, applied, verbosity)
        direction = Forwards(verbosity=verbosity, interactive=interactive)
    if not problems:
        # What about the whole backward trace then?
        backwards = backwards(allow_rebase=target is None)
        missing_backwards = to_apply(backwards, applied)
        if missing_backwards != backwards:
            # If what's missing is a strict left segment of backwards (i.e.
            # all the higher migrations) then we need to go backwards
            workplan = to_unapply(backwards, applied)
            problems = backwards_problems(
                [x for x in backwards if not x.is_rebase()],
                applied,
                verbosity,
            )
            direction = Backwards(verbosity=verbosity, interactive=interactive)
    return direction, problems, workplan

def get_migrator(direction, db_dry_run, fake, load_initial_data):
    if not direction:
        return direction
    if db_dry_run:
        direction = DryRunMigrator(migrator=direction, ignore_fail=False)
    elif fake:
        direction = FakeMigrator(migrator=direction)
    elif load_initial_data:
        direction = LoadInitialDataMigrator(migrator=direction)
    return direction

def migrate_app(migrations, target_name=None, merge=False, fake=False, db_dry_run=False, yes=False, verbosity=0, load_initial_data=False, skip=False, database=DEFAULT_DB_ALIAS, delete_ghosts=False, ignore_ghosts=False, interactive=False):
    app_label = migrations.app_label()

    verbosity = int(verbosity)
    # Fire off the pre-migrate signal
    pre_migrate.send(None, app=app_label)
    
    # If there aren't any, quit quizically
    if not migrations:
        print "? You have no migrations for the '%s' app. You might want some." % app_label
        return
    
    # Load the entire dependency graph
    Migrations.calculate_dependencies()
    
    # Check there's no strange ones in the database
    applied = MigrationHistory.objects.filter(applied__isnull=False)
    # If we're using a different database, use that
    if database != DEFAULT_DB_ALIAS:
        applied = applied.using(database)
        south.db.db = south.db.dbs[database]
        # We now have to make sure the migrations are all reloaded, as they'll
        # have imported the old value of south.db.db.
        Migrations.invalidate_all_modules()
    
    south.db.db.debug = (verbosity > 1)
    applied = check_migration_histories(applied, delete_ghosts, ignore_ghosts)
    
    # Guess the target_name
    target = migrations.guess_migration(target_name)
    if verbosity:
        if target_name not in ('zero', None) and target.name() != target_name:
            print " - Soft matched migration %s to %s." % (target_name,
                                                           target.name())
        print "Running migrations for %s:" % app_label
    
    # Get the forwards and reverse dependencies for this target
    direction, problems, workplan = get_direction(target, applied, migrations,
                                                  verbosity, interactive)
    if problems and not (merge or skip):
        raise exceptions.InconsistentMigrationHistory(problems)
    
    # Perform the migration
    migrator = get_migrator(direction, db_dry_run, fake, load_initial_data)
    if migrator:
        migrator.print_title(target)
        success = migrator.migrate_many(target, workplan, database)
        # Finally, fire off the post-migrate signal
        if success:
            post_migrate.send(None, app=app_label)
    elif verbosity:
        # Say there's nothing.
        print '- Nothing to migrate.'
        # If we have initial data enabled, and we're at the most recent
        # migration, do initial data.
        # Note: We use a fake Forwards() migrator here. It's never used really.
        if load_initial_data:
            migrator = LoadInitialDataMigrator(migrator=Forwards(verbosity=verbosity))
            migrator.load_initial_data(target)
        # Send signal.
        post_migrate.send(None, app=app_label)