kafka-streams-KTable.adoc

KTable API — Changelog Stream

KTable is the abstraction of a changelog stream from a primary-keyed table. Each record in the changelog stream is an update on the primary-keyed table with the record key as the primary key.

KTable assumes that records from the source topic that have null keys are simply dropped.

KTable can be created directly from a Kafka topic (using StreamsBuilder.table operator), as a result of transformations on an existing KTable, or aggregations (aggregate, count, and reduce) of the following abstractions:

• KGroupedStream (KStream.groupBy and KStream.groupByKey aggregate stream operators)

• KGroupedTable

• SessionWindowedKStream (KGroupedStream.windowedBy stream operator)

• TimeWindowedKStream (KGroupedStream.windowedBy stream operator with a TimeWindows window specification)

Tip	Use Scala API for Kafka Streams to make your Kafka Streams development more pleasant if Scala is your programming language.

Table 1. KTable API / Operators

Operator	Description
filter	KTable<K, V> filter( Predicate<? super K, ? super V> predicate) KTable<K, V> filter( Predicate<? super K, ? super V> predicate, Materialized<K, V, KeyValueStore<Bytes, byte[]>> materialized)
filterNot	KTable<K, V> filterNot( Predicate<? super K, ? super V> predicate) KTable<K, V> filterNot( Predicate<? super K, ? super V> predicate, Materialized<K, V, KeyValueStore<Bytes, byte[]>> materialized)
groupBy	KGroupedTable<KR, VR> groupBy( KeyValueMapper<? super K, ? super V, KeyValue<KR, VR>> selector) KGroupedTable<KR, VR> groupBy( KeyValueMapper<? super K, ? super V, KeyValue<KR, VR>> selector, Grouped<KR, VR> grouped)
join	KTable<K, VR> join( KTable<K, VO> other, ValueJoiner<? super V, ? super VO, ? extends VR> joiner) KTable<K, VR> join( KTable<K, VO> other, ValueJoiner<? super V, ? super VO, ? extends VR> joiner, Materialized<K, VR, KeyValueStore<Bytes, byte[]>> materialized)
leftJoin	KTable<K, VR> leftJoin( KTable<K, VO> other, ValueJoiner<? super V, ? super VO, ? extends VR> joiner) KTable<K, VR> leftJoin( KTable<K, VO> other, ValueJoiner<? super V, ? super VO, ? extends VR> joiner, Materialized<K, VR, KeyValueStore<Bytes, byte[]>> materialized)
mapValues	KTable<K, VR> mapValues( ValueMapper<? super V, ? extends VR> mapper) KTable<K, VR> mapValues( ValueMapper<? super V, ? extends VR> mapper, Materialized<K, VR, KeyValueStore<Bytes, byte[]>> materialized) KTable<K, VR> mapValues( ValueMapperWithKey<? super K, ? super V, ? extends VR> mapper) KTable<K, VR> mapValues( ValueMapperWithKey<? super K, ? super V, ? extends VR> mapper, Materialized<K, VR, KeyValueStore<Bytes, byte[]>> materialized)
outerJoin	KTable<K, VR> outerJoin( KTable<K, VO> other, ValueJoiner<? super V, ? super VO, ? extends VR> joiner) KTable<K, VR> outerJoin( KTable<K, VO> other, ValueJoiner<? super V, ? super VO, ? extends VR> joiner, Materialized<K, VR, KeyValueStore<Bytes, byte[]>> materialized)
queryableStoreName	String queryableStoreName()
suppress	KTable<K, V> suppress( Suppressed<? super K> suppressed)
toStream	KStream<K, V> toStream() KStream<KR, V> toStream( KeyValueMapper<? super K, ? super V, ? extends KR> mapper)
transformValues	KTable<K, VR> transformValues( ValueTransformerWithKeySupplier<? super K, ? super V, ? extends VR> transformerSupplier, Materialized<K, VR, KeyValueStore<Bytes, byte[]>> materialized, String... stateStoreNames) KTable<K, VR> transformValues( ValueTransformerWithKeySupplier<? super K, ? super V, ? extends VR> transformerSupplier, String... stateStoreNames)