[GitHub] spark pull request #22713: [SPARK-25691][SQL] Use semantic equality in Optim...

[cloud-fan <gi...@git.apache.org>]

Github user cloud-fan commented on a diff in the pull request:

    https://github.com/apache/spark/pull/22713#discussion_r225025827
  
    --- Diff: sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/RemoveRedundantAliasAndProjectSuite.scala ---
    @@ -124,4 +124,11 @@ class RemoveRedundantAliasAndProjectSuite extends PlanTest with PredicateHelper
         val expected = Subquery(relation.select('a as "a", 'b).where('b < 10).select('a).analyze)
         comparePlans(optimized, expected)
       }
    +
    +  test("SPARK-25691: RemoveRedundantProject works also with different cases") {
    +    val relation = LocalRelation('a.int, 'b.int)
    +    val query = relation.select('A, 'b).analyzeCaseInsensitive
    +    val optimized = Optimize.execute(query)
    +    comparePlans(optimized, relation)
    --- End diff --
    
    I agree that using `==` on attributes is error-prone, but we should update then one-by-one, to narrow down the scope and make sure the change is reasonable.
    
    For instance, I don't think this is a valid case. If we optimize it, the final schema field names will change, which is a breaking change if this plan an input of a parquet writing plan. (the result parquet files will have a different schema)


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