bbejeck commented on code in PR #18865:
URL: https://github.com/apache/kafka/pull/18865#discussion_r1953378378
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streams/src/main/java/org/apache/kafka/streams/kstream/KStream.java:
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@@ -909,28 +908,42 @@ <VRight, VOut> KStream<K, VOut> leftJoin(final KStream<K,
VRight> rightStream,
final StreamJoined<K, V, VRight>
streamJoined);
/**
- * Join records of this stream with another {@code KStream}'s records
using windowed outer equi join with default
- * serializers and deserializers.
- * In contrast to {@link #join(KStream, ValueJoiner, JoinWindows)
inner-join} or
- * {@link #leftJoin(KStream, ValueJoiner, JoinWindows) left-join}, all
records from both streams will produce at
- * least one output record (cf. below).
- * The join is computed on the records' key with join attribute {@code
thisKStream.key == otherKStream.key}.
+ * Join records of this (left) stream with another (right) {@code
KStream}'s records using a windowed outer equi-join.
+ * In contrast to an {@link #join(KStream, ValueJoiner, JoinWindows) inner
join} or
+ * {@link #leftJoin(KStream, ValueJoiner, JoinWindows) left join}, all
records from both stream will produce at
+ * least one output record (more details below).
+ * The join is computed using the records' key as join attribute, i.e.,
{@code leftRecord.key == rightRight.key}.
* Furthermore, two records are only joined if their timestamps are close
to each other as defined by the given
* {@link JoinWindows}, i.e., the window defines an additional join
predicate on the record timestamps.
- * <p>
- * For each pair of records meeting both join predicates the provided
{@link ValueJoiner} will be called to compute
- * a value (with arbitrary type) for the result record.
- * The key of the result record is the same as for both joining input
records.
- * Furthermore, for each input record of both {@code KStream}s that does
not satisfy the join predicate the provided
- * {@link ValueJoiner} will be called with a {@code null} value for
this/other stream, respectively.
- * If an input record value is {@code null} the record will not be
included in the join operation and thus no
- * output record will be added to the resulting {@code KStream}.
- * <p>
- * Example (assuming all input records belong to the correct windows):
+ *
+ * <p>For each pair of records meeting both join predicates the provided
{@link ValueJoiner} will be called to
+ * compute a value (with arbitrary type) for the result record.
+ * Furthermore, for each input record of either {@code KStream} that does
not have any join-partner in the other
+ * stream (i.e., no record with the same key within the join interval),
{@link ValueJoiner} will be called with a
+ * {@code null} value for right/left stream, respectively.
+ *
+ * <p>Note: By default, non-joining records from either stream are
buffered until their join window closes, and
+ * corresponding outer-join results for these records are emitted with
some delay.
+ * If you want to get outer-join results without any delay, you can use
{@link JoinWindows#of(Duration)
+ * JoinWindows#of(Duration) [deprecated]} instead.
Review Comment:
no concerns - feel free to merge
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