[ https://issues.apache.org/jira/browse/KAFKA-4217?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Matthias J. Sax updated KAFKA-4217: ----------------------------------- Description: {{KStream.transform}} gives you access to state stores while allowing you to return zero or one transformed {{KeyValue}}. Alas, it is unclear what method you should use if you want to access state stores and return zero or multiple {{KeyValue}}. Presumably you can use {{transform}}, always return {{null}}, and use {{ProcessorContext.forward}} to emit {{KeyValues}}. It may be good to introduce a {{transform}}-like {{flatMap}} equivalent, or allow store access from other {{KStream}} methods, such as {{flatMap}} itself. KIP: [https://cwiki.apache.org/confluence/display/KAFKA/KIP-313%3A+Add+KStream.flatTransform+and+KStream.flatTransformValues] was: {{KStream.transform}} gives you access to state stores while allowing you to return zero or one transformed {{KeyValue}}. Alas, it is unclear what method you should use if you want to access state stores and return zero or multiple {{KeyValue}}. Presumably you can use {{transform}}, always return {{null}}, and use {{ProcessorContext.forward}} to emit {{KeyValues}}. It may be good to introduce a {{transform}}-like {{flatMap}} equivalent, or allow store access from other {{KStream}} methods, such as {{flatMap}} itself. > KStream.transform equivalent of flatMap > --------------------------------------- > > Key: KAFKA-4217 > URL: https://issues.apache.org/jira/browse/KAFKA-4217 > Project: Kafka > Issue Type: Improvement > Components: streams > Affects Versions: 0.10.0.1 > Reporter: Elias Levy > Assignee: Bruno Cadonna > Priority: Major > Labels: api, needs-kip, newbie > Fix For: 2.2.0 > > > {{KStream.transform}} gives you access to state stores while allowing you to > return zero or one transformed {{KeyValue}}. Alas, it is unclear what method > you should use if you want to access state stores and return zero or multiple > {{KeyValue}}. Presumably you can use {{transform}}, always return {{null}}, > and use {{ProcessorContext.forward}} to emit {{KeyValues}}. > It may be good to introduce a {{transform}}-like {{flatMap}} equivalent, or > allow store access from other {{KStream}} methods, such as {{flatMap}} itself. > KIP: > [https://cwiki.apache.org/confluence/display/KAFKA/KIP-313%3A+Add+KStream.flatTransform+and+KStream.flatTransformValues] -- This message was sent by Atlassian JIRA (v7.6.3#76005)