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From cloud-fan <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-14939][SQL] Add FoldablePropagation opt...
Date Wed, 11 May 2016 04:54:24 GMT
Github user cloud-fan commented on a diff in the pull request:

    https://github.com/apache/spark/pull/12719#discussion_r62791648
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
    @@ -650,15 +646,15 @@ object FoldablePropagation extends Rule[LogicalPlan] {
     
         if (foldableExprSet.isEmpty) {
           plan
    -    } else if (hasCommandOrUnion(plan)) {
    -      replaceInSubplan(plan)
         } else {
           val foldableMap = AttributeMap(foldableExprSet.toSeq.map(_.asInstanceOf[Alias])
             .map(a => (a.toAttribute, a.child)))
     
    -      CleanupAliases(plan.transformAllExpressions {
    -        case a : AttributeReference if foldableMap.contains(a) =>
    -          Alias(foldableMap.getOrElse(a.toAttribute, a), a.name)()
    +      CleanupAliases(plan.transformUp {
    +        case p: LogicalPlan if !hasCommandOrUnion(p) => p.transformAllExpressions
{
    +          case a: AttributeReference if foldableMap.contains(a) =>
    +            Alias(foldableMap.getOrElse(a.toAttribute, a), a.name)()
    +        }
    --- End diff --
    
    I'd like to write:
    ```
    var stop = false
    plan.transformUp {
      case u: Union =>
        stop = true
        u
      case c: Command =>
        stop = true
        c
      case p if !stop => p.transformExpressions {
        case a: AttributeReference if foldableMap.contains(a) =>
          foldableMap(a) // foldableMap's value shoud be Alias, not its child
      }
    }
    ```
    
    if earlier sibling is `Union`, this is suboptimal, but still safe(it's ok to not apply
this optimization for some corner cases)


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