LQXshane commented on code in PR #15740:
URL: https://github.com/apache/kafka/pull/15740#discussion_r1650218909
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streams/src/main/java/org/apache/kafka/streams/kstream/KStream.java:
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@@ -685,6 +685,41 @@ <VR> KStream<K, VR> flatMapValues(final ValueMapper<?
super V, ? extends Iterabl
<VR> KStream<K, VR> flatMapValues(final ValueMapperWithKey<? super K, ?
super V, ? extends Iterable<? extends VR>> mapper,
final Named named);
+ /**
+ * Marking the {@code KStream} as partitioned signals the stream is
partitioned as intended,
+ * and does not require further repartitioning by downstream key changing
operations.
+ * <p>
+ * Note that {@link KStream#markAsPartitioned()} SHOULD NOT be used with
interactive query(IQ) or {@link KStream#join}.
+ * For reasons that when repartitions happen, records are physically
shuffled by a composite key defined in the stateful operation.
+ * However, if the repartitions were cancelled, records stayed in their
original partition by its original key. IQ or joins
+ * assumes and uses the composite key instead of the original key.
Review Comment:
@mjsax
Sorry for the confusion, the javadoc here can be better written...Before I
do that, the composite key notion came from the original discussion
[here](https://lists.apache.org/thread/r7yqsoqsox0z2mzxt33r9r99tnwvb58o) -
nonetheless I should remove it. Perhaps a brief description that `interactive
query might fail when trying to guess the original key`.
As for Joins, I might need your help. Most of my understanding of the
problem came from the discussion thread.
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