docs: def upgrade():
      """Upgrade database."""
      op.create_table(
          'pidstore_pid',
          sa.Column('created', sa.DateTime(), nullable=False),
          sa.Column('updated', sa.DateTime(), nullable=False),
          sa.Column('id', sa.Integer(), nullable=False),
          sa.Column('pid_type', sa.String(length=6), nullable=False),
          sa.Column('pid_value', sa.String(length=255), nullable=False),
          sa.Column('pid_provider', sa.String(length=8), nullable=True),
          sa.Column('status', sa.CHAR(1), nullable=False),
          sa.Column('object_type', sa.String(length=3), nullable=True),
          sa.Column(
              'object_uuid',
              sqlalchemy_utils.types.uuid.UUIDType(),
              nullable=True
          ),
          sa.PrimaryKeyConstraint('id')
      )
      op.create_index(
          'idx_object', 'pidstore_pid', ['object_type', 'object_uuid'],
          unique=False
      )
      op.create_index('idx_status', 'pidstore_pid', ['status'], unique=False)
      op.create_index(
          'uidx_type_pid', 'pidstore_pid', ['pid_type', 'pid_value'],
          unique=True
      )
      op.create_table(
          'pidstore_recid',
          sa.Column('recid', sa.BigInteger(), nullable=False),
          sa.PrimaryKeyConstraint('recid')
      )
      op.create_table(
          'pidstore_redirect',
          sa.Column('created', sa.DateTime(), nullable=False),
          sa.Column('updated', sa.DateTime(), nullable=False),
          sa.Column(
              'id',
              sqlalchemy_utils.types.uuid.UUIDType(),
              nullable=False
          ),
          sa.Column('pid_id', sa.Integer(), nullable=False),
          sa.ForeignKeyConstraint(
              ['pid_id'],
              [u'pidstore_pid.id'],
              onupdate='CASCADE',
              ondelete='RESTRICT'
          ),
          sa.PrimaryKeyConstraint('id')
      )