org.apache.hadoop.mapred.lib.aggregate

类 ValueAggregatorBaseDescriptor

java.lang.Object

org.apache.hadoop.mapred.lib.aggregate.ValueAggregatorBaseDescriptor

所有已实现的接口:

ValueAggregatorDescriptor

直接已知子类:

AggregateWordCount.WordCountPlugInClass, AggregateWordHistogram.AggregateWordHistogramPlugin

public class ValueAggregatorBaseDescriptor
extends Object
implements ValueAggregatorDescriptor

This class implements the common functionalities of the subclasses of ValueAggregatorDescriptor class.

字段概要

字段

限定符和类型	字段和说明
static String	DOUBLE_VALUE_SUM
String	inputFile
static String	LONG_VALUE_MAX
static String	LONG_VALUE_MIN
static String	LONG_VALUE_SUM
static String	STRING_VALUE_MAX
static String	STRING_VALUE_MIN
static String	UNIQ_VALUE_COUNT
static String	VALUE_HISTOGRAM

从接口继承的字段 org.apache.hadoop.mapred.lib.aggregate.ValueAggregatorDescriptor

ONE, TYPE_SEPARATOR

构造器概要

构造器

构造器和说明
ValueAggregatorBaseDescriptor()

方法概要

方法

限定符和类型	方法和说明
void	configure(JobConf job) get the input file name.
static Map.Entry<Text,Text>	generateEntry(String type, String id, Text val)
ArrayList<Map.Entry<Text,Text>>	generateKeyValPairs(Object key, Object val) Generate 1 or 2 aggregation-id/value pairs for the given key/value pair.
static ValueAggregator	generateValueAggregator(String type)

从类继承的方法 java.lang.Object

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

字段详细资料

UNIQ_VALUE_COUNT

public static final String UNIQ_VALUE_COUNT

另请参阅:

常量字段值

LONG_VALUE_SUM

public static final String LONG_VALUE_SUM

另请参阅:

常量字段值

DOUBLE_VALUE_SUM

public static final String DOUBLE_VALUE_SUM

另请参阅:

常量字段值

VALUE_HISTOGRAM

public static final String VALUE_HISTOGRAM

另请参阅:

常量字段值

LONG_VALUE_MAX

public static final String LONG_VALUE_MAX

另请参阅:

常量字段值

LONG_VALUE_MIN

public static final String LONG_VALUE_MIN

另请参阅:

常量字段值

STRING_VALUE_MAX

public static final String STRING_VALUE_MAX

另请参阅:

常量字段值

STRING_VALUE_MIN

public static final String STRING_VALUE_MIN

另请参阅:

常量字段值

inputFile

public String inputFile

构造器详细资料

ValueAggregatorBaseDescriptor

public ValueAggregatorBaseDescriptor()

方法详细资料

generateEntry

public static Map.Entry<Text,Text> generateEntry(String type,
                                 String id,
                                 Text val)

参数:

type - the aggregation type

id - the aggregation id

val - the val associated with the id to be aggregated

返回:

an Entry whose key is the aggregation id prefixed with the aggregation type.

generateValueAggregator

public static ValueAggregator generateValueAggregator(String type)

参数:

type - the aggregation type

返回:

a value aggregator of the given type.

generateKeyValPairs

public ArrayList<Map.Entry<Text,Text>> generateKeyValPairs(Object key,
                                                  Object val)

Generate 1 or 2 aggregation-id/value pairs for the given key/value pair. The first id will be of type LONG_VALUE_SUM, with "record_count" as its aggregation id. If the input is a file split, the second id of the same type will be generated too, with the file name as its aggregation id. This achieves the behavior of counting the total number of records in the input data, and the number of records in each input file.

指定者:

generateKeyValPairs 在接口中 ValueAggregatorDescriptor

参数:

key - input key

val - input value

返回:

a list of aggregation id/value pairs. An aggregation id encodes an aggregation type which is used to guide the way to aggregate the value in the reduce/combiner phrase of an Aggregate based job.

configure

public void configure(JobConf job)

get the input file name.

指定者:

configure 在接口中 ValueAggregatorDescriptor

参数:

job - a job configuration object