Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/1981#discussion_r64710283
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/plan/logical/operators.scala
---
@@ -298,11 +333,34 @@ case class Join(
val resolvedJoin = super.validate(tableEnv).asInstanceOf[Join]
if (!resolvedJoin.condition.forall(_.resultType == BOOLEAN_TYPE_INFO))
{
failValidation(s"filter expression ${resolvedJoin.condition} is not
a boolean")
- } else if (!ambiguousName.isEmpty) {
+ } else if (ambiguousName.nonEmpty) {
failValidation(s"join relations with ambiguous names:
${ambiguousName.mkString(", ")}")
}
+
+ resolvedJoin.condition.foreach(testJoinCondition(_))
resolvedJoin
}
+
+ 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.")
+ }
+
+ var equiJoinFound = false
+ def validateConditions(exp: Expression) : Unit = exp match {
--- End diff --
Checking whether it is an equi-join is a bit more difficult. For instance
`l.a = r.b AND (l.c = r.d OR l.c = r.e)` is a valid equi-join condition. The
first condition `(l.a = r.b)` can be pushed in the DataSet join
(`left.join(right).where(a).equalTo(b)`) and the remaining condition can be
evaluated in the `JoinFunction`.
To do the check, the predicate should be first normalized into "Conjunctive
Normal Form" (CNF). Once that is done, the check is easy.
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