[FLINK-10958] Add overload support for user defined function

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.9.0
• Component/s: Table SQL / API
• Labels: pull-request-available
• Assignee: Dian Fu
• Reporter: Dian Fu
• Created: 21/Nov/18 08:16
• Updated: 05/Aug/19 09:05
• Resolved: 22/Jul/19 07:21

Description

Currently overload is not supported in user defined function and given the following UDF

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)

Queries such as the following will compile failed with error msg "Found multiple 'eval' methods which match the signature."

 

val udf = new Func21
val table = ...
table.select(udf(new GraduatedStudent("test"))) 

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.

 

Issue Links

• relates to: FLINK-13580 Add overload support for user defined function to blink-planner
• links to: GitHub Pull Request #7152