Unknown call expression: avg(amount) when use distinct() in Flink Thanks~!

[Appleyuchi]

I posted this question here.

http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Unknown-call-expression-avg-amount-when-use-distinct-in-Flink-Thanks-td40905.html

but my replies to it is now delivered,it's strange.

Flink1.12

scala2.12

Could anyone help me?

Thanks~!