Github user vanzin commented on a diff in the pull request:
https://github.com/apache/spark/pull/18231#discussion_r120767926
--- Diff:
common/network-shuffle/src/main/java/org/apache/spark/network/shuffle/ExternalShuffleBlockHandler.java
---
@@ -209,4 +190,47 @@ private ShuffleMetrics() {
}
}
+ private class ManagedBufferIterator implements Iterator<ManagedBuffer> {
+
+ private int index = 0;
+ private String appId;
+ private String execId;
+ private String shuffleId;
+ // mapId and reduceId are stored as bytes to save memory.
+ private byte[][] mapIdAndReduceIds;
+
+ ManagedBufferIterator(String appId, String execId, String[] blockIds) {
+ this.appId = appId;
+ this.execId = execId;
+ String blockId = blockIds[0];
+ String[] blockIdParts = blockId.split("_");
+ if (blockIdParts.length < 4) {
+ throw new IllegalArgumentException("Unexpected block id format: "
+ blockId);
+ } else if (!blockIdParts[0].equals("shuffle")) {
+ throw new IllegalArgumentException("Expected shuffle block id,
got: " + blockId);
+ }
+ this.shuffleId = blockIdParts[1];
+ mapIdAndReduceIds = new byte[blockIds.length][];
+ if (blockIds.length > 0) {
+ for (int i = 0; i< blockIds.length; i++) {
+ mapIdAndReduceIds[i] = (blockIdParts[2] + "_" +
blockIdParts[3]).getBytes();
--- End diff --
Instead of storing this as a byte array, how about storing them as ints or
longs (depending on what's the actual data type of the id)?
e.g., instead of:
```
private byte[][] mapIdAndReduceIds;
```
Which results in `blockIds.length + 1` arrays in total, you could have a
single one where for each block id you have two entries, one for map id and one
for reduce id, or something along those lines.
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