def migrate_db(self, ctx, config, from_tree, to_tree):
def alembic(against, *args, hide='out'):
alembic_path = Path(against) / 'src'
with cd(str(alembic_path)):
return run('alembic -x url={dsn} '.format(dsn=database) + ' '.join(args), hide=hide)
database = ctx.qabel.block.psql_dsn
if from_tree:
current_commit = get_tree_commit(from_tree)
to_commit = get_tree_commit(to_tree)
# We are upgrading if the current current commit is an ancestor (precedes) the commit we are deploying.
# Otherwise it's an downgrade. This is important because we need to use the correct alembic folder
# which must hold the more recent revision. Alembic also needs to know whether it's an upgrade or
# downgrade, it can't figure this out on it's own.
upgrading = commit_is_ancestor(current_commit, to_commit)
# map "abcdef (head)" to just "abcdef". Empty output means no DB state ("None")
current_revision = alembic(from_tree, 'current').stdout.strip().split(' ')[0] or None
else:
upgrading = True
current_revision = None
# map "Rev: 129sdjsakdasd (head)" (+ extra lines) to just "129sdjsakdasd"
to_revision = alembic(to_tree, 'history -vr +0:').stdout.split('\n')[0].split()[1]
if current_revision == to_revision:
print('No database migration required (alembic revision {rev})'.format(rev=current_revision))
return
print('Current database is at alembic revision', current_revision)
print('Migrating to alembic revision', to_revision)
alembic_verb = 'upgrade' if upgrading else 'downgrade'
against = to_tree if upgrading else from_tree
alembic(against, alembic_verb, to_revision, hide=None)
def migrate_db(self, ctx, config, from_tree, to_tree):
def manage_py(against, args, hide='out'):
return manage_command(against, config, args, hide=hide)
def get_migrations(tree):
# showmigrations output looks like this:
# <app label>
# [X] <migration name> <-- applied migration
# [ ] <migration> <-- not applied
line_prefix_length = len(' [X] ')
all_migrations = manage_py(tree, 'showmigrations').stdout.splitlines()
app_migrations = {}
while all_migrations:
current_app = all_migrations.pop(0)
migrations = []
while all_migrations and all_migrations[0].startswith(' ['):
migrations.append(all_migrations.pop(0))
# migrations is now a list of " [x] nnnn_...", find last applied and the last overall migration
last_migration = migrations[-1][line_prefix_length:]
applied_migrations = filter(lambda m: m.startswith(' [X] '), migrations)
last_applied_migration = None
for last_applied_migration in applied_migrations:
pass
if last_applied_migration:
last_applied_migration = last_applied_migration[line_prefix_length:]
app_migrations[current_app] = last_applied_migration, last_migration
return app_migrations
if from_tree:
current_commit = get_tree_commit(from_tree)
to_commit = get_tree_commit(to_tree)
# We are upgrading if the current current commit is an ancestor (precedes) the commit we are deploying.
# Otherwise it's an downgrade. This is important because we need to use the tree which has the most currently
# applied migration when downgrading, since the downgraded-to-tree cannot undo migrations it doesn't know.
upgrading = commit_is_ancestor(current_commit, to_commit)
else:
# If we have no old tree it's always a straight upgrade of everything
upgrading = True
print('Database is being', 'upgraded' if upgrading else 'downgraded')
if upgrading:
manage_py(to_tree, 'migrate')
else:
if from_tree:
from_migrations = get_migrations(from_tree)
else:
from_migrations = {}
to_migrations = get_migrations(to_tree)
not_migrated = []
for application, (_, target_migration) in to_migrations.items():
try:
applied_migration, _ = from_migrations[application]
except KeyError:
applied_migration = '<None/Unknown>'
if applied_migration == target_migration:
not_migrated.append(application)
continue
print('Migrating \'{app}\': {applied} -> {target}'.format(app=application, applied=applied_migration,
target=target_migration))
if upgrading:
against = to_tree
else:
against = from_tree
manage_py(against, 'migrate {app} {target}'.format(app=application, target=target_migration))
print('No migrations needed for:', ', '.join(not_migrated))
