Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/6141#discussion_r31379184
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/basicOperators.scala
---
@@ -34,6 +35,32 @@ case class Project(projectList: Seq[NamedExpression],
child: LogicalPlan) extend
!expressions.exists(!_.resolved) && childrenResolved &&
!hasSpecialExpressions
}
+
+ /**
+ * Attempt to resolve an ambiguous attribute resolution.
+ * e.g. df1.join(df2, df1("key") === df2("key")).select("key")
+ *
+ * @param name name of the attribute which is ambiguous
+ * @param resolver resolver for comparing attributes
+ * @param ambiguousReferences the references which matched the name
+ * @return Some([[NamedExpression]]) if the ambiguity can be resolved,
otherwise None
+ */
+ override protected def resolveAmbiguous(
+ name: String,
+ resolver: Resolver,
+ ambiguousReferences: Seq[(Attribute, List[String])]):
Option[NamedExpression] =
+ this.child match {
+
+ // case where select is from an inner join where join keys resolve
to the same string
+ case _ @ Join(_,_,Inner,Some(EqualTo(leftExpr:NamedExpression,
rightExpr:NamedExpression)))
--- End diff --
This is too promising, what if something like `t1.a = t2.a and t1.c > 1`?
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