cloud-fan commented on a change in pull request #29342:
URL: https://github.com/apache/spark/pull/29342#discussion_r470463130
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File path: core/src/main/java/org/apache/spark/unsafe/map/BytesToBytesMap.java
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@@ -428,6 +428,68 @@ public MapIterator destructiveIterator() {
return new MapIterator(numValues, new Location(), true);
}
+ /**
+ * Iterator for the entries of this map. This is to first iterate over key
index array
+ * `longArray` then accessing values in `dataPages`. NOTE: this is different
from `MapIterator`
+ * in the sense that key index is preserved here
+ * (See `UnsafeHashedRelation` for example of usage).
+ */
+ public final class MapIteratorWithKeyIndex implements Iterator<Location> {
+
+ /**
+ * The index in `longArray` where the key is stored.
+ */
+ private int keyIndex = 0;
+
+ private int numRecords;
+ private final Location loc;
+
+ private MapIteratorWithKeyIndex() {
+ this.numRecords = numValues;
+ this.loc = new Location();
+ }
+
+ @Override
+ public boolean hasNext() {
+ return numRecords > 0;
+ }
+
+ @Override
+ public Location next() {
+ if (!loc.isDefined() || !loc.nextValue()) {
+ while (longArray.get(keyIndex * 2) == 0) {
+ keyIndex++;
+ }
+ loc.with(keyIndex, 0, true);
+ keyIndex++;
+ }
+ numRecords--;
+ return loc;
+ }
+ }
+
+ /**
+ * Returns an iterator for iterating over the entries of this map,
+ * by first iterating over the key index inside hash map's `longArray`.
+ *
+ * For efficiency, all calls to `next()` will return the same {@link
Location} object.
+ *
+ * The returned iterator is NOT thread-safe. If the map is modified while
iterating over it,
+ * the behavior of the returned iterator is undefined.
+ */
+ public MapIteratorWithKeyIndex iteratorWithKeyIndex() {
+ return new MapIteratorWithKeyIndex();
+ }
+
+ /**
+ * The maximum number of allowed keys index.
+ *
+ * The value of allowed keys index is in the range of [0, maxNumKeysIndex -
1].
+ */
+ public int maxNumKeysIndex() {
Review comment:
maybe `maxAllowedKeyIndex` is more accurate.
e.g. it's possible that the max key index is 90 while the `longArray` can
hold 100 keys. So the `maxAllowedKeyIndex` is 100 not 90.
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