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.AbstractEncoder<T>

org.apache.accumulo.core.client.lexicoder.impl.AbstractLexicoder<org.apache.accumulo.core.util.ComparablePair<A,B>>

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

All Implemented Interfaces:

Encoder<org.apache.accumulo.core.util.ComparablePair<A,B>>, Lexicoder<org.apache.accumulo.core.util.ComparablePair<A,B>>, org.apache.accumulo.core.iterators.TypedValueCombiner.Encoder<org.apache.accumulo.core.util.ComparablePair<A,B>>

public class PairLexicoder<A extends Comparable<A>,B extends Comparable<B>>
extends org.apache.accumulo.core.client.lexicoder.impl.AbstractLexicoder<org.apache.accumulo.core.util.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:

 
 StringLexicoder strEncoder = new StringLexicoder();
 ReverseLexicoder<Date> dateEnc = new ReverseLexicoder<>(new DateLexicoder());
 PairLexicoder<String,Date> pair = new PairLexicoder<>(strEncoder, dateEnc);
 long now = System.currentTimeMillis();
 byte[] pair1 = pair.encode(new ComparablePair<>("com", new Date(now)));
 byte[] pair2 = pair.encode(new ComparablePair<>("com", new Date(now + 500)));
 byte[] pair3 = pair.encode(new ComparablePair<>("org", new Date(now + 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

Modifier and Type	Method and Description
org.apache.accumulo.core.util.ComparablePair<A,B>	decode(byte[] b)
protected org.apache.accumulo.core.util.ComparablePair<A,B>	decodeUnchecked(byte[] data, int offset, int len) Decodes a byte array without checking if the offset and len exceed the bounds of the actual array.
byte[]	encode(org.apache.accumulo.core.util.ComparablePair<A,B> data)

Methods inherited from class org.apache.accumulo.core.client.lexicoder.AbstractEncoder

decode

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(org.apache.accumulo.core.util.ComparablePair<A,B> data)

decode

public org.apache.accumulo.core.util.ComparablePair<A,B> decode(byte[] b)

Specified by:

decode in interface org.apache.accumulo.core.iterators.TypedValueCombiner.Encoder<org.apache.accumulo.core.util.ComparablePair<A extends Comparable<A>,B extends Comparable<B>>>

Overrides:

decode in class AbstractEncoder<org.apache.accumulo.core.util.ComparablePair<A extends Comparable<A>,B extends Comparable<B>>>

decodeUnchecked

protected org.apache.accumulo.core.util.ComparablePair<A,B> decodeUnchecked(byte[] data,
                                                                            int offset,
                                                                            int len)

Description copied from class: AbstractEncoder

Decodes a byte array without checking if the offset and len exceed the bounds of the actual array.

Specified by:

decodeUnchecked in class AbstractEncoder<org.apache.accumulo.core.util.ComparablePair<A extends Comparable<A>,B extends Comparable<B>>>