[GitHub] [spark] chasingegg commented on pull request #35290: [SPARK-37865][SQL][3.0]Fix union bug when the first child of union has duplicate columns

[GitBox <gi...@apache.org>]

chasingegg commented on pull request #35290:
URL: https://github.com/apache/spark/pull/35290#issuecomment-1034924638


   I am still not very clear about your approach, maybe I misunderstand it. So if we have select a, a union a, b. And assume we get `1, 1 union 1, 2`, the correct result is  `(1, 1), (1, 2)`. As your approach goes, if we `select a from (select a, a union a, b)`, it will produce `1, 1`, am I right? But I think it is proper to make such sql broken because it is ambiguous, `1, 1` or `1, 2` are neither correct. If my understanding is right, I would prefer to fix it only in the master with my approach.


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