Github user sunjincheng121 commented on a diff in the pull request:
https://github.com/apache/flink/pull/4200#discussion_r124439457
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/UserDefinedFunction.scala
---
@@ -40,6 +40,12 @@ abstract class UserDefinedFunction extends Serializable {
@throws(classOf[Exception])
def close(): Unit = {}
+ /**
+ * @return true iff a call to this function is guaranteed to always
return
+ * the same result given the same parameters; true is assumed
by default
+ */
+ def isDeterministic: Boolean = true
--- End diff --
I suggest explain when user need to overwrite the method, what the impact
if not overwrite the method.
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