Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/1981#discussion_r64742780
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/plan/logical/operators.scala
---
@@ -342,21 +368,29 @@ case class Join(
}
private def testJoinCondition(expression: Expression): Unit = {
- def checkIfJoinCondition(exp : Expression) = if
(exp.children.exists(!_.isInstanceOf[JoinFieldReference])) {
- failValidation(s"Only join predicates supported. For non-join
predicates use Table#where.")
- }
+ def checkIfJoinCondition(exp : BinaryComparison) =
+ if (exp.children match {
--- End diff --
The condition looks good but can be a bit simplified like this:
```
exp.children match {
case (x: JoinFieldReference) :: (y: JoinFieldReference) :: Nil
if x.isFromLeftInput != y.isFromLeftInput
=> // predicate references both inputs. All good!
case _ => failValidation(
s"Only join predicates supported. For non-join predicates use
Table#where.")
}
```
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