org.apache.beam.sdk.schemas.transforms

Class Join

java.lang.Object

org.apache.beam.sdk.schemas.transforms.Join

@Experimental(value=SCHEMAS)
public class Join
extends java.lang.Object

A transform that performs equijoins across two schema PCollections.

This transform allows joins between two input PCollections simply by specifying the fields to join on. The resulting PCollection<Row> will have two fields named "lhs" and "rhs" respectively, each with the schema of the corresponding input PCollection.

For example, the following demonstrates joining two PCollections using a natural join on the "user" and "country" fields, where both the left-hand and the right-hand PCollections have fields with these names.

  PCollection<Row> joined = pCollection1.apply(Join.innerJoin(pCollection2).using("user", "country"));
 

If the right-hand PCollection contains fields with different names to join against, you can specify them as follows:

 PCollection<Row> joined = pCollection1.apply(Join.innerJoin(pCollection2)
       .on(FieldsEqual.left("user", "country").right("otherUser", "otherCountry")));
 

Full outer joins, left outer joins, and right outer joins are also supported.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Join.FieldsEqual Predicate object to specify fields to compare when doing an equi-join.
static class	Join.Impl<LhsT,RhsT> Implementation class .

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	LHS_TAG
static java.lang.String	RHS_TAG

Constructor Summary

Constructors

Constructor and Description
Join()

Method Summary

Modifier and Type	Method and Description
static <LhsT,RhsT> Join.Impl<LhsT,RhsT>	fullOuterJoin(PCollection<RhsT> rhs) Perform a full outer join.
static <LhsT,RhsT> Join.Impl<LhsT,RhsT>	innerJoin(PCollection<RhsT> rhs) Perform an inner join.
static <LhsT,RhsT> Join.Impl<LhsT,RhsT>	leftOuterJoin(PCollection<RhsT> rhs) Perform a left outer join.
static <LhsT,RhsT> Join.Impl<LhsT,RhsT>	rightOuterJoin(PCollection<RhsT> rhs) Perform a right outer join.

Methods inherited from class java.lang.Object

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

Field Detail

LHS_TAG

public static final java.lang.String LHS_TAG

See Also:

Constant Field Values

RHS_TAG

public static final java.lang.String RHS_TAG

See Also:

Constant Field Values

Constructor Detail

Join

public Join()

Method Detail

innerJoin

public static <LhsT,RhsT> Join.Impl<LhsT,RhsT> innerJoin(PCollection<RhsT> rhs)

Perform an inner join.

fullOuterJoin

public static <LhsT,RhsT> Join.Impl<LhsT,RhsT> fullOuterJoin(PCollection<RhsT> rhs)

Perform a full outer join.

leftOuterJoin

public static <LhsT,RhsT> Join.Impl<LhsT,RhsT> leftOuterJoin(PCollection<RhsT> rhs)

Perform a left outer join.

rightOuterJoin

public static <LhsT,RhsT> Join.Impl<LhsT,RhsT> rightOuterJoin(PCollection<RhsT> rhs)

Perform a right outer join.