old_contents: from sqlalchemy import *
  
  from sqlalchemy.orm import mapper, clear_mappers, create_session, relationship, backref
  
  from deliver.db.models.message import Message
  from deliver.db.models.digest import Digest
  
  class BaseDBWrapper(object):
  
      def _create_tables(self):
  
          metadata = MetaData()
          metadata.bind = self.engine
          self.messages = self._create_table('messages', metadata,
                                             Column('id', String(256), primary_key=True),
                                             Column('content', Text, nullable=False),
                                             Column('received_at', DateTime, nullable=False),
                                             Column('sent_at', DateTime))
  
          self.digests = self._create_table('digests', metadata,
                                            Column('msg_id', String(256), ForeignKey('messages.id', ondelete='cascade'),
                                                   primary_key=True),
                                            Column('send_to', String(256), primary_key=True),
                                            Column('scheduled_at', DateTime, nullable=False),
                                            Column('sent_at', DateTime))
  
          metadata.bind = self.engine
          metadata.create_all(self.engine)
  
          clear_mappers()
          mapper(Message, self.messages, properties={
                  'digests': relationship(Digest, backref='msg')
                  })
          mapper(Digest, self.digests)
  
          self.session = create_session()
  
      def __del__(self):
          self.session.close()
  
      def _create_table(self, name, metadata, *columns):
          return Table(name, metadata, *columns, **self._table_options())
  
new_contents: from sqlalchemy import *
  
  from sqlalchemy.orm import mapper, clear_mappers, create_session, relationship, backref
  
  from deliver.db.models.message import Message
  from deliver.db.models.digest import Digest
  
  class BaseDBWrapper(object):
  
      def _create_tables(self):
  
          metadata = MetaData()
          metadata.bind = self.engine
          self.messages = self._create_table('messages', metadata,
                                             Column('id', String(192), primary_key=True),
                                             Column('content', Text, nullable=False),
                                             Column('received_at', DateTime, nullable=False),
                                             Column('sent_at', DateTime))
  
          self.digests = self._create_table('digests', metadata,
                                            Column('msg_id', String(192), ForeignKey('messages.id', ondelete='cascade'),
                                                   primary_key=True),
                                            Column('send_to', String(192), primary_key=True),
                                            Column('scheduled_at', DateTime, nullable=False),
                                            Column('sent_at', DateTime))
  
          metadata.bind = self.engine
          metadata.create_all(self.engine)
  
          clear_mappers()
          mapper(Message, self.messages, properties={
                  'digests': relationship(Digest, backref='msg')
                  })
          mapper(Digest, self.digests)
  
          self.session = create_session()
  
      def __del__(self):
          self.session.close()
  
      def _create_table(self, name, metadata, *columns):
          return Table(name, metadata, *columns, **self._table_options())
  
subject: fix key size for mysql