[jira] [Commented] (FLINK-10958) Add overload support for user defined function

["Chesnay Schepler (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-10958?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16886028#comment-16886028 ] 

Chesnay Schepler commented on FLINK-10958:
------------------------------------------

[~sunjincheng121] What's the state of this issue? I saw that we merged _something_; can we close this issue?

> Add overload support for user defined function 
> -----------------------------------------------
>
>                 Key: FLINK-10958
>                 URL: https://issues.apache.org/jira/browse/FLINK-10958
>             Project: Flink
>          Issue Type: Improvement
>          Components: Table SQL / API
>            Reporter: Dian Fu
>            Assignee: Dian Fu
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.9.0
>
>
> 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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