Github user squito commented on a diff in the pull request:
https://github.com/apache/spark/pull/6423#discussion_r32050912
--- Diff:
core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleReader.scala ---
@@ -33,17 +34,52 @@ private[spark] class HashShuffleReader[K, C](
"Hash shuffle currently only supports fetching one partition")
private val dep = handle.dependency
+ private val blockManager = SparkEnv.get.blockManager
/** Read the combined key-values for this reduce task */
override def read(): Iterator[Product2[K, C]] = {
+ val blockStreams = BlockStoreShuffleFetcher.fetchBlockStreams(
+ handle.shuffleId, startPartition, context)
+
+ // Wrap the streams for compression based on configuration
+ val wrappedStreams = blockStreams.map { case (blockId, inputStream) =>
+ blockManager.wrapForCompression(blockId, inputStream)
+ }
+
val ser = Serializer.getSerializer(dep.serializer)
- val iter = BlockStoreShuffleFetcher.fetch(handle.shuffleId,
startPartition, context, ser)
+ val serializerInstance = ser.newInstance()
+
+ // Create a key/value iterator for each stream
+ val recordIterator = wrappedStreams.flatMap { wrappedStream =>
+ val kvIter =
serializerInstance.deserializeStream(wrappedStream).asKeyValueIterator
+ CompletionIterator[(Any, Any), Iterator[(Any, Any)]](kvIter, {
+ // Close the stream once all the records have been read from it
+ wrappedStream.close()
--- End diff --
and can you also expand the comment a bit here that the
`CompletionIterator` necessary to free underlying ManagedBuffers as soon as
possible (but there is already a `TaskCompletionListener` to guarantee the
buffer is released even if there is an exception).
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