org.apache.kafka.streams.kstream

Interface KGroupedTable<K,V>

Type Parameters:

K - Type of primary keys

V - Type of value changes

@InterfaceStability.Unstable
public interface KGroupedTable<K,V>

KGroupedTable is an abstraction of a grouped changelog stream from a primary-keyed table, usually on a different grouping key than the original primary key.

It is an intermediate representation after a re-grouping of a KTable before an aggregation is applied to the new partitions resulting in a new KTable.

Method Summary

Methods

Modifier and Type	Method and Description
<T> KTable<K,T>	aggregate(Initializer<T> initializer, Aggregator<K,V,T> adder, Aggregator<K,V,T> subtractor, Serde<T> aggValueSerde, String storeName) Aggregate updating values of this stream by the selected key into a new instance of KTable.
<T> KTable<K,T>	aggregate(Initializer<T> initializer, Aggregator<K,V,T> adder, Aggregator<K,V,T> subtractor, String storeName) Aggregate updating values of this stream by the selected key into a new instance of KTable using default serializers and deserializers.
KTable<K,Long>	count(String storeName) Count number of records of this stream by the selected key into a new instance of KTable.
KTable<K,V>	reduce(Reducer<V> adder, Reducer<V> subtractor, String storeName) Combine updating values of this stream by the selected key into a new instance of KTable.

Method Detail

reduce

KTable<K,V> reduce(Reducer<V> adder,
                 Reducer<V> subtractor,
                 String storeName)

Combine updating values of this stream by the selected key into a new instance of KTable. The resulting KTable will be materialized in a local state store with the given store name. Also a changelog topic named "${applicationId}-${storeName}-changelog" will be automatically created in Kafka for failure recovery, where "applicationID" is specified by the user in StreamsConfig.

Parameters:

adder - the instance of Reducer for addition

subtractor - the instance of Reducer for subtraction

storeName - the name of the underlying KTable state store

Returns:

a KTable with the same key and value types as this KGroupedTable, containing aggregated values for each key

aggregate

<T> KTable<K,T> aggregate(Initializer<T> initializer,
                        Aggregator<K,V,T> adder,
                        Aggregator<K,V,T> subtractor,
                        Serde<T> aggValueSerde,
                        String storeName)

Aggregate updating values of this stream by the selected key into a new instance of KTable. The resulting KTable will be materialized in a local state store with the given store name. Also a changelog topic named "${applicationId}-${storeName}-changelog" will be automatically created in Kafka for failure recovery, where "applicationID" is specified by the user in StreamsConfig.

Type Parameters:

T - the value type of the aggregated KTable

Parameters:

initializer - the instance of Initializer

adder - the instance of Aggregator for addition

subtractor - the instance of Aggregator for subtraction

aggValueSerde - value serdes for materializing the aggregated table, if not specified the default serdes defined in the configs will be used

storeName - the name of the underlying KTable state store

Returns:

a KTable with same key and aggregated value type T, containing aggregated values for each key

aggregate

<T> KTable<K,T> aggregate(Initializer<T> initializer,
                        Aggregator<K,V,T> adder,
                        Aggregator<K,V,T> subtractor,
                        String storeName)

Aggregate updating values of this stream by the selected key into a new instance of KTable using default serializers and deserializers. The resulting KTable will be materialized in a local state store with the given store name. Also a changelog topic named "${applicationId}-${storeName}-changelog" will be automatically created in Kafka for failure recovery, where "applicationID" is specified by the user in StreamsConfig.

Type Parameters:

T - the value type of the aggregated KTable

Parameters:

initializer - the instance of Initializer

adder - the instance of Aggregator for addition

subtractor - the instance of Aggregator for subtraction

storeName - the name of the underlying KTable state store

Returns:

a KTable with same key and aggregated value type T, containing aggregated values for each key

count

KTable<K,Long> count(String storeName)

Count number of records of this stream by the selected key into a new instance of KTable. The resulting KTable will be materialized in a local state store with the given store name. Also a changelog topic named "${applicationId}-${storeName}-changelog" will be automatically created in Kafka for failure recovery, where "applicationID" is specified by the user in StreamsConfig.

Parameters:

storeName - the name of the underlying KTable state store

Returns:

a KTable with same key and Long value type as this KGroupedTable, containing the number of values for each key