[FLINK-3698] Scala Option can't be used as a key

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Duplicate
• Assignee: Chiwan Park
• Reporter: Timur Fayruzov
• Created: 04/Apr/16 22:11
• Updated: 28/Feb/19 13:20
• Resolved: 26/Apr/16 08:49

Description

Discussion: http://mail-archives.apache.org/mod_mbox/flink-user/201603.mbox/%3CCAO0MGUjWQaovvUvAB%3DBYrwQzA0ocFtMy4%3DV%3DP--343Sy1V5BSg%40mail.gmail.com%3E

Option should be treated the same way as other generic objects where it can be used as a key if generic argument implements Comparable.
Here's a scalatest in FunSpec format that illustrates the issue:
```
case class MyKey(x: Option[String])

it("can't use options inside classes used as keys") {
val a = env.fromCollection(Seq(MyKey(Some("a")), MyKey(Some("c"))))
val b = env.fromCollection(Seq(MyKey(Some("a")), MyKey(Some("z"))))
intercept[InvalidProgramException]

{ a.coGroup(b) .where(e => e) .equalTo(e => e) }

// workaround
a.coGroup(b)
.where(e => e.toString) // `e` should be translated to any object that implements Comparable interface to be a valid key.
.equalTo(e => e.toString)
}
```

Issue Links

• duplicates: FLINK-2673 Scala API does not support Option type as key