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https://issues.apache.org/jira/browse/FLINK-13580?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16899928#comment-16899928
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Timo Walther commented on FLINK-13580:
--------------------------------------
This issue should be solved after FLIP-37 part 2 has been implemented.
> Add overload support for user defined function to blink-planner
> ---------------------------------------------------------------
>
> Key: FLINK-13580
> URL: https://issues.apache.org/jira/browse/FLINK-13580
> Project: Flink
> Issue Type: New Feature
> Components: Table SQL / Planner
> Reporter: Jingsong Lee
> Priority: Major
> Fix For: 1.10.0
>
>
> Currently overload is not supported in user defined function and given the
> following UDF
> {code:java}
> class Func21 extends ScalarFunction {
> def eval(p: People): String = {
> p.name
> }
> def eval(p: Student): String = {
> "student#" + p.name
> }
> }
> class People(val name: String)
> class Student(name: String) extends People(name)
> class GraduatedStudent(name: String) extends Student(name)
> {code}
> Queries such as the following will compile failed with error msg "Found
> multiple 'eval' methods which match the signature."
>
> {code:java}
> val udf = new Func21
> val table = ...
> table.select(udf(new GraduatedStudent("test"))) {code}
> That's because overload is not supported in user defined function currently.
> I think it will make sense to support overload following the java language
> specification in section
> [15.2|https://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.12].
>
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