Mark Tranter created KAFKA-7653:
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Summary: Streams-Scala: Add type level differentiation for Key and
Value serdes.
Key: KAFKA-7653
URL: https://issues.apache.org/jira/browse/KAFKA-7653
Project: Kafka
Issue Type: Improvement
Components: streams
Reporter: Mark Tranter
Implicit resolution/conversion of Serdes/Consumed etc is a big improvement for
the Scala Streams API. However in cases where a user needs to differentiate
between Key and Value serializer functionality (i.e. using the Schema
Registry), implicit resolution doesn't help and could cause issues.
e.g.
{code:java}
case class MouseClickEvent(pageId: Long, userId: String)
builder
// Long serde taken from implicit scope configured with
// `isKey` = true
.stream[Long, MouseClickEvent]("mouse-clicks")
.selectKey((_,v) => v.userId)
.groupByKey
.aggregate(() => 0L, (_: String, mce: MouseClickEvent, count: Long) => count
+ 1)
.toStream
// Same Long serde taken from implicit scope configured with
// `isKey` = true, even thought the `Long` value in this case
// will be the Value
.to("mouse-clicks-by-user")
{code}
It would be ideal if Key and Value Serde/SerdeWrapper types/type classes could
be introduced to overcome this limitation.
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