guozhangwang commented on code in PR #12555:
URL: https://github.com/apache/kafka/pull/12555#discussion_r961002924
##########
streams/src/main/java/org/apache/kafka/streams/kstream/internals/InternalStreamsBuilder.java:
##########
@@ -356,6 +381,95 @@ private void mergeDuplicateSourceNodes() {
}
}
+ /**
+ * If the join is a self-join, remove the node KStreamJoinWindow
corresponding to the
+ */
+ @SuppressWarnings("unchecked")
+ private void rewriteSelfJoin(final GraphNode currentNode, final
Set<GraphNode> visited) {
+ visited.add(currentNode);
+ if (currentNode instanceof StreamStreamJoinNode &&
isSelfJoin(currentNode)) {
+ ((StreamStreamJoinNode) currentNode).setSelfJoin();
+ // Remove JoinOtherWindowed node
+ final GraphNode parent =
currentNode.parentNodes().stream().findFirst().get();
+ GraphNode left = null, right = null;
+ for (final GraphNode child: parent.children()) {
+ if (child instanceof ProcessorGraphNode
+ && isStreamJoinWindowNode((ProcessorGraphNode) child)) {
+ if (left == null) {
+ left = child;
+ } else {
+ right = child;
+ }
+ }
+ }
+ // Sanity check
+ if (left != null && right != null && left.buildPriority() <
right.buildPriority()) {
+ parent.removeChild(right);
+ }
+ }
+ for (final GraphNode child: currentNode.children()) {
+ if (!visited.contains(child)) {
+ rewriteSelfJoin(child, visited);
+ }
+ }
+ }
+
+ /**
+ * The self-join rewriting can be applied if:
+ * 1. The path from the StreamStreamJoinNode to the root contains a single
source node.
+ * 2. The StreamStreamJoinNode has a single parent.
+ * 3. There are no other nodes besides the KStreamJoinWindow that are
siblings of the
+ * StreamStreamJoinNode and have smaller build priority.
Review Comment:
Just curious, in the above case, logically speaking since we are not
reassigning the map-valued result stream back to stream1 like `stream1 =
stream1.mapValues()`, this step is basically a no-op and should not affect
stream1 right?
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
