Package org.apache.hadoop.mapreduce.lib.aggregate

Class ValueAggregatorBaseDescriptor

java.lang.Object

org.apache.hadoop.mapreduce.lib.aggregate.ValueAggregatorBaseDescriptor

All Implemented Interfaces:

ValueAggregatorDescriptor

Direct Known Subclasses:

ValueAggregatorBaseDescriptor

@Public
@Stable
public class ValueAggregatorBaseDescriptor
extends Object
implements ValueAggregatorDescriptor

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

Field Summary

Fields

Modifier and Type	Field	Description
static final String	DOUBLE_VALUE_SUM
String	inputFile
static final String	LONG_VALUE_MAX
static final String	LONG_VALUE_MIN
static final String	LONG_VALUE_SUM
static final String	STRING_VALUE_MAX
static final String	STRING_VALUE_MIN
static final String	UNIQ_VALUE_COUNT
static final String	VALUE_HISTOGRAM

Fields inherited from interface org.apache.hadoop.mapreduce.lib.aggregate.ValueAggregatorDescriptor

ONE, TYPE_SEPARATOR

Constructor Summary

Constructors

Constructor	Description
ValueAggregatorBaseDescriptor()

Method Summary

Modifier and Type	Method	Description
void	configure(Configuration conf)	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, long uniqCount)

Methods inherited from class java.lang.Object

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

Field Details

UNIQ_VALUE_COUNT

public static final String UNIQ_VALUE_COUNT

See Also:

• Constant Field Values

LONG_VALUE_SUM

public static final String LONG_VALUE_SUM

See Also:

• Constant Field Values

DOUBLE_VALUE_SUM

public static final String DOUBLE_VALUE_SUM

See Also:

• Constant Field Values

VALUE_HISTOGRAM

public static final String VALUE_HISTOGRAM

See Also:

• Constant Field Values

LONG_VALUE_MAX

public static final String LONG_VALUE_MAX

See Also:

• Constant Field Values

LONG_VALUE_MIN

public static final String LONG_VALUE_MIN

See Also:

• Constant Field Values

STRING_VALUE_MAX

public static final String STRING_VALUE_MAX

See Also:

• Constant Field Values

STRING_VALUE_MIN

public static final String STRING_VALUE_MIN

See Also:

• Constant Field Values

inputFile

public String inputFile

Constructor Details

ValueAggregatorBaseDescriptor

public ValueAggregatorBaseDescriptor()

Method Details

generateEntry

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

Parameters:

type - the aggregation type

id - the aggregation id

val - the val associated with the id to be aggregated

Returns:

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

generateValueAggregator

public static ValueAggregator generateValueAggregator(String type,
 long uniqCount)

Parameters:

type - the aggregation type

uniqCount - the limit in the number of unique values to keep, if type is UNIQ_VALUE_COUNT

Returns:

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.

Specified by:

generateKeyValPairs in interface ValueAggregatorDescriptor

Parameters:

key - input key

val - input value

Returns:

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(Configuration conf)

get the input file name.

Specified by:

configure in interface ValueAggregatorDescriptor

Parameters:

conf - a configuration object