public class LeftJoin extends BaseJoiner
Iterator
that will iterate over a given Joiner
and return tuples that represent
a left inner, right outer join of the CoGrouper internal grouped tuple collections.
Note only the farthest right tuple stream will be used as the outer join. All preceding joins to the left will
be inner joins. See MixedJoin
for more flexibility.
Joins perform based on the equality of the join keys. In the case of null values, Java treats two
null values as equivalent. SQL does not treat null values as equal. To produce SQL like results in a given
join, a new Comparator
will need to be used on the joined values to prevent null from
equaling null. As a convenience, see the NullNotEquivalentComparator
class.MixedJoin
,
Serialized FormModifier and Type | Class and Description |
---|---|
static class |
LeftJoin.JoinIterator |
Constructor and Description |
---|
LeftJoin() |
LeftJoin(Fields fieldDeclaration) |
Modifier and Type | Method and Description |
---|---|
Iterator<Tuple> |
getIterator(JoinerClosure closure)
Returns an iterator that joins the given CoGroupClosure co-groups.
|
int |
numJoins()
Returns the number of joins this instance can handle.
|
getFieldDeclaration
public LeftJoin()
@ConstructorProperties(value="fieldDeclaration") public LeftJoin(Fields fieldDeclaration)
public Iterator<Tuple> getIterator(JoinerClosure closure)
Joiner
closure
- of type GroupClosureCopyright © 2007-2015 Concurrent, Inc. All Rights Reserved.