org.apache.crunch.lib

Class Aggregate

java.lang.Object

org.apache.crunch.lib.Aggregate

public class Aggregate
extends Object

Methods for performing various types of aggregations over PCollection instances.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Aggregate.PairValueComparator<K,V>
static class	Aggregate.TopKCombineFn<K,V>
static class	Aggregate.TopKFn<K,V>

Constructor Summary

Constructors

Constructor and Description
Aggregate()

Method Summary

Methods

Modifier and Type	Method and Description
static <K,V> PTable<K,Collection<V>>	collectValues(PTable<K,V> collect)
static <S> PTable<S,Long>	count(PCollection<S> collect) Returns a PTable that contains the unique elements of this collection mapped to a count of their occurrences.
static <S> PObject<Long>	length(PCollection<S> collect) Returns the number of elements in the provided PCollection.
static <S> PObject<S>	max(PCollection<S> collect) Returns the largest numerical element from the input collection.
static <S> PObject<S>	min(PCollection<S> collect) Returns the smallest numerical element from the input collection.
static <K,V> PTable<K,V>	top(PTable<K,V> ptable, int limit, boolean maximize)

Methods inherited from class java.lang.Object

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

Constructor Detail

Aggregate

public Aggregate()

Method Detail

count

public static <S> PTable<S,Long> count(PCollection<S> collect)

Returns a PTable that contains the unique elements of this collection mapped to a count of their occurrences.

length

public static <S> PObject<Long> length(PCollection<S> collect)

Returns the number of elements in the provided PCollection.

Type Parameters:

S - The type of the PCollection.

Parameters:

collect - The PCollection whose elements should be counted.

Returns:

A PObject containing the number of elements in the PCollection.

top

public static <K,V> PTable<K,V> top(PTable<K,V> ptable,
                    int limit,
                    boolean maximize)

max

public static <S> PObject<S> max(PCollection<S> collect)

Returns the largest numerical element from the input collection.

min

public static <S> PObject<S> min(PCollection<S> collect)

Returns the smallest numerical element from the input collection.

collectValues

public static <K,V> PTable<K,Collection<V>> collectValues(PTable<K,V> collect)