Github user nsyca commented on a diff in the pull request:
https://github.com/apache/spark/pull/14719#discussion_r80714835
--- Diff: sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala
---
@@ -1580,6 +1583,28 @@ class DataFrameSuite extends QueryTest with
SharedSQLContext {
assert(df.persist.take(1).apply(0).toSeq(100).asInstanceOf[Long] ==
100)
}
+ test("""SPARK-17154: df("column_name") should return correct result when
we do self-join""") {
--- End diff --
I don't think we should support a self-join of the same Dataset/DateFrame
of the same name. That is,
`df.join(df)`
should be blocked. We can ask the user to express it as
`df.join(df.as("df2"))`
, which is clearer. We certainly must not support
`df.join(df, df("col1") === df("col2")`
, which blindly put `"col1"` and `"col2"` to the first `df`. @sarutak 's
solution does change the behaviour to an error.
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