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The following commit(s) were added to refs/heads/2.6 by this push:
new 078f7d4 KAFKA-6453: Document how timestamps are computed for
aggregations and joins (#9009)
078f7d4 is described below
commit 078f7d4b77b61ba7a5a894bf6b240fb8cc366059
Author: Jim Galasyn <[email protected]>
AuthorDate: Mon Jul 13 15:01:14 2020 -0700
KAFKA-6453: Document how timestamps are computed for aggregations and joins
(#9009)
Reviewer: Matthias J. Sax <[email protected]>
---
docs/streams/core-concepts.html | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)
diff --git a/docs/streams/core-concepts.html b/docs/streams/core-concepts.html
index 43e1502..d8cbd7a 100644
--- a/docs/streams/core-concepts.html
+++ b/docs/streams/core-concepts.html
@@ -128,7 +128,33 @@
</ul>
<p>
- Note, that the describe default behavior can be changed in the
Processor API by assigning timestamps to output records explicitly when calling
<code>#forward()</code>.
+ You can change the default behavior in the Processor API by assigning
+ timestamps to output records explicitly when calling
<code>#forward()</code>.
+ </p>
+
+ <p>
+ For aggregations and joins, timestamps are computed by using the
+ following rules.
+ </p>
+
+ <p>
+ <ul>
+ <li>For joins (stream-stream, table-table) that have left and right
+ input records, the timestamp of the output record is assigned
+ <code>max(left.ts, right.ts)</code>.</li>
+ <li>For stream-table joins, the output record is assigned the
timestamp
+ from the stream record.</li>
+ <li>For aggregations, Kafka Streams also computes the
<code>max</code>
+ timestamp over all records, per key, either globally (for
non-windowed)
+ or per-window.</li>
+ <li>For stateless operations, the input record timestamp is passed
through.
+ For <code>flatMap</code> and siblings that emit multiple
records, all
+ output records inherit the timestamp from the corresponding
input record.</li>
+ </ul>
+ </p>
+
+ <p>
+
</p>
<h3><a id="streams_concepts_aggregations"
href="#streams_concepts_aggregations">Aggregations</a></h3>
