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[SPARK-23129][CORE] Make deserializeStream of DiskMapIterator init lazily #20292

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[SPARK-23129][CORE] Make deserializeStream of DiskMapIterator init lazily #20292

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[SPARK][CORE] Make deserializeStream of DiskMapIterator init lazily
caneGuy Jan 17, 2018
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caneGuy Jan 18, 2018
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caneGuy Jan 25, 2018
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17 changes: 10 additions & 7 deletions core/src/main/scala/org/apache/spark/util/collection/ExternalAppendOnlyMap.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -463,7 +463,7 @@ class ExternalAppendOnlyMap[K, V, C](

// An intermediate stream that reads from exactly one batch
// This guards against pre-fetching and other arbitrary behavior of higher level streams
private var deserializeStream = nextBatchStream()
private var deserializeStream: DeserializationStream = null
private var nextItem: (K, C) = null
private var objectsRead = 0

Expand Down Expand Up @@ -528,27 +528,30 @@ class ExternalAppendOnlyMap[K, V, C](
override def hasNext: Boolean = {
if (nextItem == null) {
if (deserializeStream == null) {
return false
// In case of deserializeStream has not been initialized
deserializeStream = nextBatchStream()
if (deserializeStream == null) {
return false
}
}
nextItem = readNextItem()
}
nextItem != null
}

override def next(): (K, C) = {
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@cloud-fan cloud-fan Jan 24, 2018

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nit:

if (!hasNext) {
  throw new NoSuchElementException
}
val item = nextItem
nextItem = null
item

val item = if (nextItem == null) readNextItem() else nextItem
if (item == null) {
if (!hasNext) {
throw new NoSuchElementException
}
val item = nextItem
nextItem = null
item
}

private def cleanup() {
batchIndex = batchOffsets.length // Prevent reading any other batch
val ds = deserializeStream
if (ds != null) {
ds.close()
if (deserializeStream != null) {
deserializeStream.close()
deserializeStream = null
}
if (fileStream != null) {
Expand Down