Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/13484#discussion_r65752894
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/trees/TreeNode.scala
---
@@ -169,11 +170,24 @@ abstract class TreeNode[BaseType <:
TreeNode[BaseType]] extends Product {
}
/**
+ * Efficient alternative to `productIterator.map(f).toArray`.
+ */
+ protected def mapProductIterator[B: ClassTag](f: Any => B): Array[B] = {
+ val arr = Array.ofDim[B](productArity)
+ var i = 0
+ while (i < arr.length) {
+ arr(i) = f(productElement(i))
--- End diff --
It turns out that ProductIterator was maintaining its own internal counter
and was calling `productElement(i)`:
```scala
/** An iterator over all the elements of this product.
* @return in the default implementation, an `Iterator[Any]`
*/
def productIterator: Iterator[Any] = new
scala.collection.AbstractIterator[Any] {
private var c: Int = 0
private val cmax = productArity
def hasNext = c < cmax
def next() = { val result = productElement(c); c += 1; result }
}
```
Calling `productElement` ourselves here avoids another layer of object
allocation and buys a bit of additional perf. boost.
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