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https://issues.apache.org/jira/browse/KAFKA-3561?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15303877#comment-15303877
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Damian Guy commented on KAFKA-3561:
-----------------------------------
Guozhang - i'd like to do this if it is ok with you. I'm going to need a bit of
guidance though.
It looks to me that I'd need to change the signature of map to something like:
{code}
<K1, V1> KStream<K1, V1> map(final KeyValueMapper<K, V, KeyValue<K1, V1>>
mapper,
final Serde<K1> keySerde,
final Serde<V1> valueSerde,
final String topic);
{code}
and then it could be implemented like so:
{code}
@Override
public <K1, V1> KStream<K1, V1> map(final KeyValueMapper<K, V, KeyValue<K1,
V1>> mapper,
final Serde<K1> keySerde,
final Serde<V1> valueSerde,
final String topic) {
String name = topology.newName(MAP_NAME);
topology.addProcessor(name, new KStreamMap<>(mapper), this.name);
return new KStreamImpl<K1, V1>(topology, name, null).through(keySerde,
valueSerde, topic);
}
{code}
What other methods does this apply to. What am I missing? (I'm sure there is a
lot of context i'm missing)
Thanks,
Damian
> Auto create through topic for KStream aggregation and join
> ----------------------------------------------------------
>
> Key: KAFKA-3561
> URL: https://issues.apache.org/jira/browse/KAFKA-3561
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Reporter: Guozhang Wang
> Assignee: Damian Guy
> Labels: api
> Fix For: 0.10.1.0
>
>
> For KStream.join / aggregateByKey operations that requires the streams to be
> partitioned on the record key, today users should repartition themselves
> through the "through" call:
> {code}
> stream1 = builder.stream("topic1");
> stream2 = builder.stream("topic2");
> stream3 = stream1.map(/* set the right key for join*/).through("topic3");
> stream4 = stream2.map(/* set the right key for join*/).through("topic4");
> stream3.join(stream4, ..)
> {code}
> This pattern can actually be done by the Streams DSL itself instead of
> requiring users to specify themselves, i.e. users can just set the right key
> like (see KAFKA-3430) and then call join, which will be translated by adding
> the "internal topic for repartition".
> Another thing is that today if user do not call "through" after setting a new
> key, the aggregation result would not be correct as the aggregation is based
> on key B while the source partitions is partitioned by key A and hence each
> task will only get a partial aggregation for all keys. But this is not
> validated in the DSL today. We should do both the auto-translation and
> validation.
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