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org.apache.crunch
Class FilterFn<T>

java.lang.Object
  org.apache.crunch.DoFn<T,T>
      org.apache.crunch.FilterFn<T>

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

FilterFn.AndFn, FilterFn.NotFn, FilterFn.OrFn

public abstract class FilterFn<T>
extends DoFn<T,T>

A DoFn for the common case of filtering the members of a PCollection based on a boolean condition.

See Also:

Serialized Form

Nested Class Summary

static class	FilterFn.AndFn<S>
static class	FilterFn.NotFn<S>
static class	FilterFn.OrFn<S>

Constructor Summary

FilterFn()

Method Summary

abstract boolean	accept(T input) If true, emit the given record.
static <S> FilterFn<S>	and(FilterFn<S>... fns)
static <S> FilterFn<S>	not(FilterFn<S> fn)
static <S> FilterFn<S>	or(FilterFn<S>... fns)
void	process(T input, Emitter<T> emitter) Processes the records from a PCollection.
float	scaleFactor() Returns an estimate of how applying this function to a PCollection will cause it to change in side.

Methods inherited from class org.apache.crunch.DoFn

cleanup, configure, initialize, setConfigurationForTest, setContext

Methods inherited from class java.lang.Object

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

Constructor Detail

FilterFn

public FilterFn()

Method Detail

accept

public abstract boolean accept(T input)

If true, emit the given record.

process

public void process(T input,
                    Emitter<T> emitter)

Description copied from class: DoFn

Processes the records from a PCollection.

Note: Crunch can reuse a single input record object whose content changes on each DoFn.process(Object, Emitter) method call. This functionality is imposed by Hadoop's Reducer implementation: The framework will reuse the key and value objects that are passed into the reduce, therefore the application should clone the objects they want to keep a copy of.

Specified by:

process in class DoFn<T,T>

Parameters:

input - The input record.

emitter - The emitter to send the output to

scaleFactor

public float scaleFactor()

Description copied from class: DoFn

Returns an estimate of how applying this function to a PCollection will cause it to change in side. The optimizer uses these estimates to decide where to break up dependent MR jobs into separate Map and Reduce phases in order to minimize I/O.

Subclasses of DoFn that will substantially alter the size of the resulting PCollection should override this method.

Overrides:

scaleFactor in class DoFn<T,T>

and

public static <S> FilterFn<S> and(FilterFn<S>... fns)

or

public static <S> FilterFn<S> or(FilterFn<S>... fns)

not

public static <S> FilterFn<S> not(FilterFn<S> fn)