Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/9260#discussion_r42928573
--- Diff:
core/src/main/scala/org/apache/spark/util/collection/ExternalAppendOnlyMap.scala
---
@@ -214,13 +215,18 @@ class ExternalAppendOnlyMap[K, V, C](
spilledMaps.append(new DiskMapIterator(file, blockId, batchSizes))
}
+ private def freeCurrentMap(): Unit = {
+ currentMap = null // So that the memory can be garbage-collected
+ releaseMemoryForThisThread()
+ }
+
/**
* Return an iterator that merges the in-memory map with the spilled
maps.
* If no spill has occurred, simply return the in-memory map's iterator.
*/
override def iterator: Iterator[(K, C)] = {
if (spilledMaps.isEmpty) {
- currentMap.iterator
+ CompletionIterator[(K, C), Iterator[(K, C)]](currentMap.iterator,
freeCurrentMap())
--- End diff --
I debated whether to push this burden to callers rather than using a
`CompletionIterator` here until I noticed that `ExternalIterator()` ends up
calling `currentMap.destructiveSortedIterator()`, so (implicitly) this method
already had the limitation that it could only be called once.
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