jiangxb1987 commented on code in PR #40690:
URL: https://github.com/apache/spark/pull/40690#discussion_r1160971328
##########
core/src/main/scala/org/apache/spark/MapOutputTracker.scala:
##########
@@ -157,22 +164,29 @@ private class ShuffleStatus(
invalidateSerializedMapOutputStatusCache()
}
mapStatuses(mapIndex) = status
+ mapIdToMapIndex(status.mapId) = mapIndex
}
/**
* Update the map output location (e.g. during migration).
*/
def updateMapOutput(mapId: Long, bmAddress: BlockManagerId): Unit =
withWriteLock {
try {
- val mapStatusOpt = mapStatuses.find(x => x != null && x.mapId == mapId)
+ // OpenHashMap would return 0 if the key doesn't exist.
+ val mapIndex = if (mapIdToMapIndex.contains(mapId)) {
+ Some(mapIdToMapIndex(mapId))
+ } else {
+ None
+ }
Review Comment:
The problem is OpenHashMap casts null value to the declared type internally.
Thus if the key doesn't exist, it would cast `null` to Int, and the output
would be 0. It is not possible for us tell whether the key doesn't exist or the
value is really 0, without calling the `contains` function.
I'll try to follow the first option to add a `get(key): Option[V]`.
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