old_contents: """Define database schemas."""
  
  import sqlalchemy
  
  from ndscheduler import settings
  from ndscheduler import utils
  
  METADATA = sqlalchemy.MetaData()
  
  #
  # Jobs
  # It's defined by apscheduler library.
  #
  
  #
  # Executions
  #
  EXECUTIONS = sqlalchemy.Table(
      settings.EXECUTIONS_TABLENAME, METADATA,
      sqlalchemy.Column('eid', sqlalchemy.Text, primary_key=True),
      sqlalchemy.Column('hostname', sqlalchemy.Text, nullable=True),
      sqlalchemy.Column('pid', sqlalchemy.Integer, nullable=True),
      sqlalchemy.Column('state', sqlalchemy.Integer, nullable=False),
      sqlalchemy.Column('scheduled_time', sqlalchemy.DateTime(timezone=True), nullable=False,
                        default=utils.get_current_datetime),
      sqlalchemy.Column('updated_time', sqlalchemy.DateTime(timezone=True),
                        default=utils.get_current_datetime, onupdate=utils.get_current_datetime),
      sqlalchemy.Column('description', sqlalchemy.Text, nullable=True),
      sqlalchemy.Column('job_id', sqlalchemy.Text, nullable=False),
      sqlalchemy.Column('task_id', sqlalchemy.Text, nullable=True))
  
  #
  # Audit logs
  #
  AUDIT_LOGS = sqlalchemy.Table(
      settings.AUDIT_LOGS_TABLENAME, METADATA,
      sqlalchemy.Column('job_id', sqlalchemy.Text, nullable=False),
      sqlalchemy.Column('job_name', sqlalchemy.Text, nullable=False),
      sqlalchemy.Column('event', sqlalchemy.Integer, nullable=False),
      sqlalchemy.Column('user', sqlalchemy.Text, nullable=True),
      sqlalchemy.Column('created_time', sqlalchemy.DateTime(timezone=True), nullable=False,
                        default=utils.get_current_datetime),
      sqlalchemy.Column('description', sqlalchemy.Text, nullable=True))
  
new_contents: """Define database schemas."""
  
  import sqlalchemy
  
  from ndscheduler import settings
  from ndscheduler import utils
  
  METADATA = sqlalchemy.MetaData()
  
  #
  # Jobs
  # It's defined by apscheduler library.
  #
  
  #
  # Executions
  #
  EXECUTIONS = sqlalchemy.Table(
      settings.EXECUTIONS_TABLENAME, METADATA,
      sqlalchemy.Column('eid', sqlalchemy.Unicode(191, _warn_on_bytestring=False), primary_key=True),
      sqlalchemy.Column('hostname', sqlalchemy.Text, nullable=True),
      sqlalchemy.Column('pid', sqlalchemy.Integer, nullable=True),
      sqlalchemy.Column('state', sqlalchemy.Integer, nullable=False),
      sqlalchemy.Column('scheduled_time', sqlalchemy.DateTime(timezone=True), nullable=False,
                        default=utils.get_current_datetime),
      sqlalchemy.Column('updated_time', sqlalchemy.DateTime(timezone=True),
                        default=utils.get_current_datetime, onupdate=utils.get_current_datetime),
      sqlalchemy.Column('description', sqlalchemy.Text, nullable=True),
      sqlalchemy.Column('job_id', sqlalchemy.Text, nullable=False),
      sqlalchemy.Column('task_id', sqlalchemy.Text, nullable=True))
  
  #
  # Audit logs
  #
  AUDIT_LOGS = sqlalchemy.Table(
      settings.AUDIT_LOGS_TABLENAME, METADATA,
      sqlalchemy.Column('job_id', sqlalchemy.Text, nullable=False),
      sqlalchemy.Column('job_name', sqlalchemy.Text, nullable=False),
      sqlalchemy.Column('event', sqlalchemy.Integer, nullable=False),
      sqlalchemy.Column('user', sqlalchemy.Text, nullable=True),
      sqlalchemy.Column('created_time', sqlalchemy.DateTime(timezone=True), nullable=False,
                        default=utils.get_current_datetime),
      sqlalchemy.Column('description', sqlalchemy.Text, nullable=True))
  
subject: Fix MySQL compatibility.