org.apache.hadoop.mapreduce.lib.partition

类 KeyFieldBasedComparator<K,V>

java.lang.Object

org.apache.hadoop.io.WritableComparator

org.apache.hadoop.mapreduce.lib.partition.KeyFieldBasedComparator<K,V>

所有已实现的接口:

Comparator, Configurable, RawComparator

@InterfaceAudience.Public
@InterfaceStability.Stable
public class KeyFieldBasedComparator<K,V>
extends WritableComparator
implements Configurable

This comparator implementation provides a subset of the features provided by the Unix/GNU Sort. In particular, the supported features are: -n, (Sort numerically) -r, (Reverse the result of comparison) -k pos1[,pos2], where pos is of the form f[.c][opts], where f is the number of the field to use, and c is the number of the first character from the beginning of the field. Fields and character posns are numbered starting with 1; a character position of zero in pos2 indicates the field's last character. If '.c' is omitted from pos1, it defaults to 1 (the beginning of the field); if omitted from pos2, it defaults to 0 (the end of the field). opts are ordering options (any of 'nr' as described above). We assume that the fields in the key are separated by mapreduce.map.output.key.field.separator.

字段概要

字段

限定符和类型	字段和说明
static String	COMPARATOR_OPTIONS

构造器概要

构造器

构造器和说明
KeyFieldBasedComparator()

方法概要

方法

限定符和类型	方法和说明
int	compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) Optimization hook.
Configuration	getConf() Return the configuration used by this object.
static String	getKeyFieldComparatorOption(JobContext job) Get the KeyFieldBasedComparator options
void	setConf(Configuration conf) Set the configuration to be used by this object.
static void	setKeyFieldComparatorOptions(Job job, String keySpec) Set the KeyFieldBasedComparator options used to compare keys.

从类继承的方法 org.apache.hadoop.io.WritableComparator

compare, compare, compareBytes, define, get, getKeyClass, hashBytes, hashBytes, newKey, readDouble, readFloat, readInt, readLong, readUnsignedShort, readVInt, readVLong

从类继承的方法 java.lang.Object

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

从接口继承的方法 java.util.Comparator

equals

字段详细资料

COMPARATOR_OPTIONS

public static String COMPARATOR_OPTIONS

构造器详细资料

KeyFieldBasedComparator

public KeyFieldBasedComparator()

方法详细资料

setConf

public void setConf(Configuration conf)

从接口复制的说明: Configurable

Set the configuration to be used by this object.

指定者:

setConf 在接口中 Configurable

getConf

public Configuration getConf()

从接口复制的说明: Configurable

Return the configuration used by this object.

指定者:

getConf 在接口中 Configurable

compare

public int compare(byte[] b1,
          int s1,
          int l1,
          byte[] b2,
          int s2,
          int l2)

从类复制的说明: WritableComparator

Optimization hook. Override this to make SequenceFile.Sorter's scream.

The default implementation reads the data into two WritableComparables (using Writable.readFields(DataInput), then calls WritableComparator.compare(WritableComparable,WritableComparable).

指定者:

compare 在接口中 RawComparator

覆盖:

compare 在类中 WritableComparator

setKeyFieldComparatorOptions

public static void setKeyFieldComparatorOptions(Job job,
                                String keySpec)

Set the KeyFieldBasedComparator options used to compare keys.

参数:

keySpec - the key specification of the form -k pos1[,pos2], where, pos is of the form f[.c][opts], where f is the number of the key field to use, and c is the number of the first character from the beginning of the field. Fields and character posns are numbered starting with 1; a character position of zero in pos2 indicates the field's last character. If '.c' is omitted from pos1, it defaults to 1 (the beginning of the field); if omitted from pos2, it defaults to 0 (the end of the field). opts are ordering options. The supported options are: -n, (Sort numerically) -r, (Reverse the result of comparison)

getKeyFieldComparatorOption

public static String getKeyFieldComparatorOption(JobContext job)

Get the KeyFieldBasedComparator options