org.apache.accumulo.core.client.lexicoder

Class PairLexicoder<A extends Comparable<A>,B extends Comparable<B>>

java.lang.Object

org.apache.accumulo.core.client.lexicoder.PairLexicoder<A,B>

All Implemented Interfaces:

Encoder<ComparablePair<A,B>>, Lexicoder<ComparablePair<A,B>>, TypedValueCombiner.Encoder<ComparablePair<A,B>>

public class PairLexicoder<A extends Comparable<A>,B extends Comparable<B>>
extends Object
implements Lexicoder<ComparablePair<A,B>>

This class is a lexicoder that sorts a ComparablePair. Each item in the pair is encoded with the given lexicoder and concatenated together. This makes it easy to construct a sortable key based on two components. There are many examples of this- but a key/value relationship is a great one. If we decided we wanted a two-component key where the first component is a string and the second component a date which is reverse sorted, we can do so with the following example:

 {
   @code
   StringLexicoder stringEncoder = new StringLexicoder();
   ReverseLexicoder<Date> dateEncoder = new ReverseLexicoder<Date>(new DateLexicoder());
   PairLexicoder<String,Date> pairLexicoder = new PairLexicoder<String,Date>(stringEncoder, dateEncoder);
   byte[] pair1 = pairLexicoder.encode(new ComparablePair<String,Date>("com.google", new Date()));
   byte[] pair2 = pairLexicoder.encode(new ComparablePair<String,Date>("com.google", new Date(System.currentTimeMillis() + 500)));
   byte[] pair3 = pairLexicoder.encode(new ComparablePair<String,Date>("org.apache", new Date(System.currentTimeMillis() + 1000)));
 }
 

In the example, pair2 will be sorted before pair1. pair3 will occur last since 'org' is sorted after 'com'. If we just used a DateLexicoder instead of a ReverseLexicoder, pair1 would have been sorted before pair2.

Since:

1.6.0

Constructor Summary

Constructors

Constructor and Description
PairLexicoder(Lexicoder<A> firstLexicoder, Lexicoder<B> secondLexicoder)

Method Summary

Methods

Modifier and Type	Method and Description
ComparablePair<A,B>	decode(byte[] data)
byte[]	encode(ComparablePair<A,B> data)

Methods inherited from class java.lang.Object

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

Constructor Detail

PairLexicoder

public PairLexicoder(Lexicoder<A> firstLexicoder,
             Lexicoder<B> secondLexicoder)

Method Detail

encode

public byte[] encode(ComparablePair<A,B> data)

Specified by:

encode in interface TypedValueCombiner.Encoder<ComparablePair<A extends Comparable<A>,B extends Comparable<B>>>

decode

public ComparablePair<A,B> decode(byte[] data)

Specified by:

decode in interface TypedValueCombiner.Encoder<ComparablePair<A extends Comparable<A>,B extends Comparable<B>>>