Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/1447#discussion_r15037091
--- Diff: core/src/main/scala/org/apache/spark/rdd/PairRDDFunctions.scala
---
@@ -216,17 +216,17 @@ class PairRDDFunctions[K, V](self: RDD[(K, V)])
def reducePartition(iter: Iterator[(K, V)]): Iterator[JHashMap[K, V]]
= {
val map = new JHashMap[K, V]
- iter.foreach { case (k, v) =>
- val old = map.get(k)
- map.put(k, if (old == null) v else func(old, v))
+ iter.foreach { pair =>
+ val old = map.get(pair._1)
--- End diff --
can we save the key into a variable here so we don't call _1 twice?
I was looking at the bytecode generated by pattern matching versus
non-pattern-matching, and the main difference is that we bypass some
unnecessary branches:
{code}
final def apply(x0$1: Tuple2): Unit = {
case <synthetic> val x1: Tuple2 = x0$1;
case4(){
if (x1.ne(null))
{
val k: Int = x1._1$mcI$sp();
val v: Int = x1._2$mcI$sp();
matchEnd3({
scala.this.Predef.println(scala.Int.box(k.+(v)));
scala.runtime.BoxedUnit.UNIT
})
}
else
case5()
};
case5(){
matchEnd3(throw new MatchError(x1))
};
matchEnd3(x: runtime.BoxedUnit){
()
}
{code}
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