[GitHub] [kafka] vpapavas commented on a diff in pull request #12555: Optimize self-join

[GitBox]

vpapavas commented on code in PR #12555:
URL: https://github.com/apache/kafka/pull/12555#discussion_r961012010


##########
streams/src/main/java/org/apache/kafka/streams/kstream/internals/InternalStreamsBuilder.java:
##########
@@ -270,16 +272,20 @@ private void maybeAddNodeForOptimizationMetadata(final 
GraphNode node) {
 
     // use this method for testing only
     public void buildAndOptimizeTopology() {
-        buildAndOptimizeTopology(false);
+        buildAndOptimizeTopology(false, false);
     }
 
-    public void buildAndOptimizeTopology(final boolean optimizeTopology) {
+    public void buildAndOptimizeTopology(
+        final boolean optimizeTopology, final boolean optimizeSelfJoin) {
 
         mergeDuplicateSourceNodes();
         if (optimizeTopology) {
             LOG.debug("Optimizing the Kafka Streams graph for repartition 
nodes");
             optimizeKTableSourceTopics();
             maybeOptimizeRepartitionOperations();
+            if (optimizeSelfJoin) {

Review Comment:
   The logical plan will have only one source since they will get merged as 
they are referring to the same topic. Hence, all the nodes will be children of 
the source node and siblings of the join node. 
   For example,
   Case 2:
   ```
   root -> source
   source -> join-window1, join-window2, stream-join
   ```
   
   and
   Case 3:
   ```
   root -> source
   source -> join-window1, map-values1, join-window2, stream-join
   ```



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