Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/9241#discussion_r42953420
--- Diff:
core/src/main/java/org/apache/spark/unsafe/map/BytesToBytesMap.java ---
@@ -227,62 +238,147 @@ public BytesToBytesMap(
*/
public int numElements() { return numElements; }
- public static final class BytesToBytesMapIterator implements
Iterator<Location> {
+ public final class BytesToBytesMapIterator implements Iterator<Location>
{
- private final int numRecords;
- private final Iterator<MemoryBlock> dataPagesIterator;
+ private int numRecords;
private final Location loc;
private MemoryBlock currentPage = null;
- private int currentRecordNumber = 0;
+ private int recordsInPage = 0;
private Object pageBaseObject;
private long offsetInPage;
// If this iterator destructive or not. When it is true, it frees each
page as it moves onto
// next one.
private boolean destructive = false;
- private BytesToBytesMap bmap;
- private BytesToBytesMapIterator(
- int numRecords, Iterator<MemoryBlock> dataPagesIterator, Location
loc,
- boolean destructive, BytesToBytesMap bmap) {
+ private LinkedList<UnsafeSorterSpillWriter> spillWriters =
+ new LinkedList<UnsafeSorterSpillWriter>();
+ private UnsafeSorterSpillReader reader = null;
+
+ private BytesToBytesMapIterator(int numRecords, Location loc, boolean
destructive) {
this.numRecords = numRecords;
- this.dataPagesIterator = dataPagesIterator;
this.loc = loc;
this.destructive = destructive;
- this.bmap = bmap;
- if (dataPagesIterator.hasNext()) {
- advanceToNextPage();
- }
+ destructiveIterator = this;
}
private void advanceToNextPage() {
- if (destructive && currentPage != null) {
- dataPagesIterator.remove();
- this.bmap.taskMemoryManager.freePage(currentPage);
- this.bmap.shuffleMemoryManager.release(currentPage.size());
+ synchronized (this) {
+ int nextIdx = dataPages.indexOf(currentPage) + 1;
+ if (destructive && currentPage != null) {
+ dataPages.remove(currentPage);
+ taskMemoryManager.freePage(currentPage);
+ shuffleMemoryManager.release(currentPage.size());
+ nextIdx --;
+ }
+ if (dataPages.size() > nextIdx) {
+ currentPage = dataPages.get(nextIdx);
+ pageBaseObject = currentPage.getBaseObject();
+ offsetInPage = currentPage.getBaseOffset();
+ recordsInPage = Platform.getInt(pageBaseObject, offsetInPage);
+ offsetInPage += 4;
+ } else {
+ currentPage = null;
+ try {
+ reader = spillWriters.removeFirst().getReader(blockManager);
+ recordsInPage = -1;
+ } catch (IOException e) {
+ // Scala iterator does not handle exception
+ Platform.throwException(e);
+ }
+ }
}
- currentPage = dataPagesIterator.next();
- pageBaseObject = currentPage.getBaseObject();
- offsetInPage = currentPage.getBaseOffset();
}
@Override
public boolean hasNext() {
- return currentRecordNumber != numRecords;
+ return numRecords > 0;
}
@Override
public Location next() {
- int totalLength = Platform.getInt(pageBaseObject, offsetInPage);
- if (totalLength == END_OF_PAGE_MARKER) {
+ if (recordsInPage == 0) {
advanceToNextPage();
- totalLength = Platform.getInt(pageBaseObject, offsetInPage);
}
- loc.with(currentPage, offsetInPage);
- offsetInPage += 4 + totalLength;
- currentRecordNumber++;
- return loc;
+ numRecords --;
+ if (currentPage != null) {
+ int totalLength = Platform.getInt(pageBaseObject, offsetInPage);
+ loc.with(currentPage, offsetInPage);
+ offsetInPage += 4 + totalLength;
+ recordsInPage --;
+ return loc;
+ } else {
+ assert(reader != null);
+ if (!reader.hasNext()) {
+ advanceToNextPage();
+ }
+ try {
+ reader.loadNext();
+ } catch (IOException e) {
+ // Scala iterator does not handle exception
+ Platform.throwException(e);
+ }
+ loc.with(reader.getBaseObject(), reader.getBaseOffset(),
reader.getRecordLength());
+ return loc;
+ }
+ }
+
+ public long spill(long numBytes) throws IOException {
+ synchronized (this) {
+ if (!destructive || dataPages.size() == 1) {
+ return 0L;
+ }
+
+ // TODO: use existing ShuffleWriteMetrics
--- End diff --
Let's chat about this later; I'm not sure whether or not the existing
spillable collections have consistent semantics in terms accounting for spills
via shuffle write metrics. I spent a decent amount of time investigating this
earlier in the year, so I'll see if I can find my notes from then.
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