def drop_block_ss_columns(store):
 for c in ['created', 'destroyed']:
  try:
   store.sql(('ALTER TABLE block DROP COLUMN block_ss_' + c))
  except Exception:
   store.rollback()

def drop_block_ss_columns ( store ) : for c in [ 'created' , 'destroyed' ] : try : store . sql ( ( 'ALTER TABLE block DROP COLUMN block_ss_' + c ) ) except Exception : store . rollback ( )
drop columns that may have been added in error .