Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/15032#discussion_r78265127
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/AggregationIterator.scala
---
@@ -181,11 +182,7 @@ abstract class AggregationIterator(
// Process all expression-based aggregate functions.
updateProjection.target(currentBuffer)(joinedRow(currentBuffer,
row))
// Process all imperative aggregate functions.
- var i = 0
- while (i < updateFunctions.length) {
- updateFunctions(i)(currentBuffer, row)
- i += 1
- }
+ updateFunctions.foreach(updateFunction =>
updateFunction(currentBuffer, row))
--- End diff --
I just wonder if it'd make sense if we cache the length and use just a
normal `while` loop as done above. This seems not encouraged [1]. I believe
this is fine but not for critical path. IIUC, this will , at least, introduce
virtual function calls for each row. I found a blog just to be verbose to make
sure myself [2]. I am worried because this change can be a example in the
future. Maybe, we need a clear reason to change this.
[1]
https://github.com/databricks/scala-style-guide#traversal-and-zipwithindex
[2] http://www.scalablescala.com/roller/scala/entry/why_is_using_for_foreach
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