Github user hvanhovell commented on a diff in the pull request:
https://github.com/apache/spark/pull/18541#discussion_r125631060
--- Diff:
core/src/main/java/org/apache/spark/util/collection/unsafe/sort/UnsafeExternalSorter.java
---
@@ -596,17 +600,37 @@ public long getKeyPrefix() {
*
* TODO: support forced spilling
*/
- public UnsafeSorterIterator getIterator() throws IOException {
+ public UnsafeSorterIterator getIterator(int startIndex) throws
IOException {
if (spillWriters.isEmpty()) {
assert(inMemSorter != null);
- return inMemSorter.getSortedIterator();
+ UnsafeSorterIterator iter = inMemSorter.getSortedIterator();
+ for (int i = 0; i < startIndex && iter.hasNext(); i++) {
+ iter.loadNext();
+ }
+ return iter;
} else {
LinkedList<UnsafeSorterIterator> queue = new LinkedList<>();
+ int i = 0;
for (UnsafeSorterSpillWriter spillWriter : spillWriters) {
- queue.add(spillWriter.getReader(serializerManager));
+ if (i + spillWriter.recordsSpilled() <= startIndex) {
+ i += spillWriter.recordsSpilled();
+ continue;
+ } else {
+ UnsafeSorterIterator iter =
spillWriter.getReader(serializerManager);
+ for (int j = i; j < startIndex && iter.hasNext(); j++) {
+ iter.loadNext();
+ }
+ queue.add(iter);
+ i += spillWriter.recordsSpilled();
+ }
}
if (inMemSorter != null) {
- queue.add(inMemSorter.getSortedIterator());
+ UnsafeSorterIterator iter = inMemSorter.getSortedIterator();
--- End diff --
This is almost similar to the code in the first if clause. Let's try to get
rid of this duplication, and move this logic into a separate function.
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