com.hazelcast.jet

Class JoinClause<K,E0,E1,E1_OUT>

java.lang.Object

com.hazelcast.jet.JoinClause<K,E0,E1,E1_OUT>

Type Parameters:

K - the type of the join key

E0 - the type of the left-hand stream item

E1 - the type of the right-hand stream item

E1_OUT - the result type of the right-hand projection function

All Implemented Interfaces:

Serializable

public final class JoinClause<K,E0,E1,E1_OUT>
extends Object
implements Serializable

Specifies how to join an enriching stream to the primary stream in a hash-join operation. It holds three primitives:

1. left-hand key extractor: extracts the join key from the primary stream
2. right-hand key extractor: extracts the join key from the enriching stream
3. right-hand projection function: maps the enriching stream item to the item that will be in the result of the join operation.

The primary use case for the projection function is enrichment from a map source, such as Sources.map(java.lang.String). The enriching stream consists of map entries, but the result should contain just the vaules. In this case the projection function should be Entry::getValue. There is direct support for this case with the method joinMapEntries(DistributedFunction).

See Also:

Serialized Form

Method Summary

Modifier and Type	Method and Description
static <K,E0,E1_IN extends Map.Entry<K,E1>,E1> JoinClause<K,E0,E1_IN,E1>	joinMapEntries(DistributedFunction<E0,K> leftKeyFn) A shorthand factory for the common case of hash-joining with a stream of map entries.
DistributedFunction<E0,K>	leftKeyFn() Returns the left-hand key extractor function.
static <K,E0,E1> JoinClause<K,E0,E1,E1>	onKeys(DistributedFunction<E0,K> leftKeyFn, DistributedFunction<E1,K> rightKeyFn) Constructs and returns a join clause with the supplied left-hand and right-hand key extractor functions, and with an identity right-hand projection function.
<E1_NEW_OUT> JoinClause<K,E0,E1,E1_NEW_OUT>	projecting(DistributedFunction<E1,E1_NEW_OUT> rightProjectFn) Returns a copy of this join clause, but with the right-hand projection function replaced with the supplied one.
DistributedFunction<E1,K>	rightKeyFn() Returns the right-hand key extractor function.
DistributedFunction<E1,E1_OUT>	rightProjectFn() Returns the right-hand projection function.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

onKeys

public static <K,E0,E1> JoinClause<K,E0,E1,E1> onKeys(DistributedFunction<E0,K> leftKeyFn,
                                                      DistributedFunction<E1,K> rightKeyFn)

Constructs and returns a join clause with the supplied left-hand and right-hand key extractor functions, and with an identity right-hand projection function.

joinMapEntries

public static <K,E0,E1_IN extends Map.Entry<K,E1>,E1> JoinClause<K,E0,E1_IN,E1> joinMapEntries(DistributedFunction<E0,K> leftKeyFn)

A shorthand factory for the common case of hash-joining with a stream of map entries. The right key extractor is Map.Entry::getKey and the right-hand projection function is Map.Entry::getValue.

Type Parameters:

K - the type of the key

E0 - the type of the primary stream

E1 - the type of the enriching stream's entry value

E1_IN - the type of the enriching stream (Map.Entry<K, E1>)

Parameters:

leftKeyFn - the function to extract the key from the primary stream

projecting

public <E1_NEW_OUT> JoinClause<K,E0,E1,E1_NEW_OUT> projecting(DistributedFunction<E1,E1_NEW_OUT> rightProjectFn)

Returns a copy of this join clause, but with the right-hand projection function replaced with the supplied one.

leftKeyFn

public DistributedFunction<E0,K> leftKeyFn()

Returns the left-hand key extractor function.

rightKeyFn

public DistributedFunction<E1,K> rightKeyFn()

Returns the right-hand key extractor function.

rightProjectFn

public DistributedFunction<E1,E1_OUT> rightProjectFn()

Returns the right-hand projection function.