[GitHub] [flink] TanYuxin-tyx commented on a change in pull request #18474: [FLINK-25786][network] Adjust the generation of subpartition data storage order for sort-shuffle from random shuffle to random shift

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TanYuxin-tyx commented on a change in pull request #18474:
URL: https://github.com/apache/flink/pull/18474#discussion_r791322643



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File path: flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/SortMergeResultPartition.java
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@@ -492,10 +490,13 @@ public int getNumberOfQueuedBuffers(int targetSubpartition) {
     }
 
     private int[] getRandomSubpartitionOrder(int numSubpartitions) {
-        List<Integer> list =
-                IntStream.range(0, numSubpartitions).boxed().collect(Collectors.toList());
-        Collections.shuffle(list);
-        return list.stream().mapToInt(Integer::intValue).toArray();
+        int[] order = new int[numSubpartitions];
+        Random random = new Random();
+        int shift = random.nextInt(numSubpartitions);

Review comment:
       If `shift` is 0, the returned array may not be changed. 
   
   In addition, this patch may cause the actual traversal order not to change, but only the starting position to be modified. Is this expected?




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