[GitHub] [spark] LuciferYang commented on a change in pull request #35694: [SPARK-38360][SQL][SS][PYTHON] Introduce a `exists` function for `TreeNode` to eliminate duplicate code patterns

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

LuciferYang commented on a change in pull request #35694:
URL: https://github.com/apache/spark/pull/35694#discussion_r822278258



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/trees/TreeNode.scala
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@@ -246,6 +246,16 @@ abstract class TreeNode[BaseType <: TreeNode[BaseType]] extends Product with Tre
     children.foldLeft(Option.empty[BaseType]) { (l, r) => l.orElse(r.find(f)) }
   }
 
+  /**
+   * Test whether there is [[TreeNode]] satisfies the conditions specified in `f`.
+   * The condition is recursively applied to this node and all of its children (pre-order).
+   */
+  def exists(f: BaseType => Boolean): Boolean = if (f(this)) {

Review comment:
       Like
   ```scala
   def exists(pf: PartialFunction[BaseType, Boolean]): Boolean = {
       if (pf.applyOrElse(this, { _: Any => false})) {
         true
       } else {
         children.exists(c => pf.applyOrElse(c, { _: Any => false}))
       }
     }
   ```
   
   This implementation is more like `PartialFunction#cond` as follows:
   
   ```scala
    /** Creates a Boolean test based on a value and a partial function.
      *  It behaves like a 'match' statement with an implied 'case _ => false'
      *  following the supplied cases.
      *
      *  @param  x   the value to test
      *  @param  pf  the partial function
      *  @return true, iff `x` is in the domain of `pf` and `pf(x) == true`.
      */
     def cond[T](x: T)(pf: PartialFunction[T, Boolean]): Boolean = pf.applyOrElse(x, constFalse)
   ```
   
   This requires the assumption that `case _ => false`
   
   




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