vpapavas commented on code in PR #12644:
URL: https://github.com/apache/kafka/pull/12644#discussion_r977470895
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streams/src/main/java/org/apache/kafka/streams/kstream/internals/InternalStreamsBuilder.java:
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@@ -356,12 +383,55 @@ private void mergeDuplicateSourceNodes() {
}
}
- private void optimizeKTableSourceTopics() {
+
+ /**
+ * The self-join rewriting can be applied if the StreamStreamJoinNode has
a single parent.
+ * If the join is a self-join, remove the node KStreamJoinWindow
corresponding to the
+ * right argument of the join (the "other"). The join node may have
multiple siblings but for
+ * this rewriting we only care about the ThisKStreamJoinWindow and the
OtherKStreamJoinWindow.
+ * We iterate over all the siblings to identify these two nodes so that we
can remove the
+ * latter.
+ */
+ @SuppressWarnings("unchecked")
+ private void rewriteSingleStoreSelfJoin(
+ final GraphNode currentNode, final Map<GraphNode, Boolean> visited) {
+ visited.put(currentNode, true);
+ if (currentNode instanceof StreamStreamJoinNode &&
currentNode.parentNodes().size() == 1) {
+ final StreamStreamJoinNode joinNode = (StreamStreamJoinNode)
currentNode;
+ // Remove JoinOtherWindowed node
+ final GraphNode parent =
joinNode.parentNodes().stream().findFirst().get();
+ GraphNode left = null, right = null;
+ for (final GraphNode child: parent.children()) {
+ if (child instanceof WindowedStreamProcessorNode
Review Comment:
The current JoinNode might have other JoinNodes as siblings. We need to
differentiate between the `WindowedStreamProcessorNode` nodes that belong the
current node versus others.
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