[GitHub] spark pull request #16757: [SPARK-18609][SPARK-18841][SQL] Fix redundant Ali...

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

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

    https://github.com/apache/spark/pull/16757#discussion_r99357432
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala ---
    @@ -154,56 +155,108 @@ class SimpleTestOptimizer extends Optimizer(
       new SimpleCatalystConf(caseSensitiveAnalysis = true))
     
     /**
    - * Removes the Project only conducting Alias of its child node.
    - * It is created mainly for removing extra Project added in EliminateSerialization rule,
    - * but can also benefit other operators.
    + * Remove redundant aliases from a query plan. A redundant alias is an alias that does not change
    + * the name or metadata of a column, and does not deduplicate it.
      */
    -object RemoveAliasOnlyProject extends Rule[LogicalPlan] {
    +object RemoveRedundantAliases extends Rule[LogicalPlan] {
    +
       /**
    -   * Returns true if the project list is semantically same as child output, after strip alias on
    -   * attribute.
    +   * Replace the attributes in an expression using the given mapping.
    --- End diff --
    
    looks like this doc is wrong?


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