[GitHub] [kafka] mjsax commented on a change in pull request #9606: [KAFKA-10722] doc: Improve JavaDoc for KGroupedStream.aggregate

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mjsax commented on a change in pull request #9606:
URL: https://github.com/apache/kafka/pull/9606#discussion_r532996684



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File path: streams/src/main/java/org/apache/kafka/streams/kstream/KGroupedStream.java
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@@ -381,7 +381,8 @@
      * {@link StreamsConfig#COMMIT_INTERVAL_MS_CONFIG commit intervall}.
      *
      * <p>
-     * For failure and recovery the store will be backed by an internal changelog topic that will be created in Kafka.
+     * For failure and recovery the store (which always will be of type {@link TimestampedKeyValueStore}) will be backed by
+     * an internal changelog topic that will be created in Kafka.

Review comment:
       `reduce()` and `count()` are similar to `aggregate()`: reduce only does not allow you to change the value type (ie, output type == input type) and count, well implements an aggregate() that counts :)
   
   And they all work the same for `KGroupedStream`, `CogroupedKStream`, `TimeWindowedKStream` and `TimeWindowedCoGroupedKStream`.
   
   `table()` and `globalTable()` just read a topic and upsert the data into a state store / table.
   
   So it would be great to do them all in one PR?




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