[GitHub] [pinot] jasperjiaguo commented on a change in pull request #8441: Add retainInstancesSequence feature to table rebalance to minimize data movement between instances

[GitBox <gi...@apache.org>]

jasperjiaguo commented on a change in pull request #8441:
URL: https://github.com/apache/pinot/pull/8441#discussion_r840879048



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File path: pinot-controller/src/main/java/org/apache/pinot/controller/helix/core/assignment/instance/InstanceAssignmentDriver.java
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@@ -77,7 +95,31 @@ public InstancePartitions assignInstances(InstancePartitionsType instancePartiti
         new InstanceReplicaGroupPartitionSelector(assignmentConfig.getReplicaGroupPartitionConfig(), tableNameWithType);
     InstancePartitions instancePartitions = new InstancePartitions(
         instancePartitionsType.getInstancePartitionsName(TableNameBuilder.extractRawTableName(tableNameWithType)));
+    if (shouldRetainInstanceSequence) {
+      // Keep the pool to instances map if instance sequence should be retained.
+      instancePartitions
+          .setPoolToInstancesMap(extractInstanceNamesFromPoolToInstanceConfigsMap(poolToInstanceConfigsMap));
+    }

Review comment:
       Does this mean if we do not set `shouldRetainInstanceSequence` in the initial assignment, the subsequent table rebalance will not be able to retain sequence even if we set `retainInstanceSequence` in the rebalance config? Is it okay that we always persist the instance sequence in the initial assignment?




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