godfreyhe commented on a change in pull request #11321:
URL: https://github.com/apache/flink/pull/11321#discussion_r449544239
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File path:
flink-table/flink-table-common/src/main/java/org/apache/flink/table/functions/UserDefinedFunction.java
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@@ -45,10 +45,19 @@
/**
* Returns a unique, serialized representation for this function.
+ *
+ * <p>If the function has no constructor or only one constructor
without any parameter,
Review comment:
if a class contains no constructor declarations, then a default
constructor is automatically generated by the compiler. We can't distinguish
between a user-defined constructor and a compiler-generated constructor. I will
update the javadoc to `If the function has only one constructor without any
parameter (a default constructor is automatically generated by the compiler if
a class contains no constructor declarations), identifier is the class name,
else identifier is the class name and instance's md5.`
> It may contains some variable and may be changed after constructed.
That means this UDF is non-deterministic, the identifier of this UDF is also
unstable.
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