mysql.py 文件源码

def _mysql_drop_constraint(element, compiler, **kw):
    """Redefine SQLAlchemy's drop constraint to
    raise errors for invalid constraint type."""

    constraint = element.element
    if isinstance(constraint, (schema.ForeignKeyConstraint,
                               schema.PrimaryKeyConstraint,
                               schema.UniqueConstraint)
                  ):
        return compiler.visit_drop_constraint(element, **kw)
    elif isinstance(constraint, schema.CheckConstraint):
        raise NotImplementedError(
            "MySQL does not support CHECK constraints.")
    else:
        raise NotImplementedError(
            "No generic 'DROP CONSTRAINT' in MySQL - "
            "please specify constraint type")