cassandra中的按计数排序查询

我正在尝试在CQL中执行此查询

select path_name, count(*) as cont from a_data where a_id=5 group by path_name order by cont limit 10;

InvalidRequest:来自服务器的错误:code=2200[无效查询] message=“未定义的列名cont”

CQL版本信息:

cqlsh>显示版本[cqlsh 5.0.1 | Cassandra 3.11.4 | CQL spec 3.4.4|