Package org.apache.nutch.crawl

Class DeduplicationJob

java.lang.Object

org.apache.hadoop.conf.Configured

org.apache.nutch.util.NutchTool

org.apache.nutch.crawl.DeduplicationJob

All Implemented Interfaces:

Configurable, Tool

public class DeduplicationJob
extends NutchTool
implements Tool

Generic deduplicator which groups fetched URLs with the same digest and marks all of them as duplicate except the one with the highest score (based on the score in the crawldb, which is not necessarily the same as the score indexed). If two (or more) documents have the same score, then the document with the latest timestamp is kept. If the documents have the same timestamp then the one with the shortest URL is kept. The documents marked as duplicate can then be deleted with the command CleaningJob.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	DeduplicationJob.DBFilter
static class	DeduplicationJob.DedupReducer<K extends Writable>
static class	DeduplicationJob.StatusUpdateReducer	Combine multiple new entries for a url.

Field Summary

Fields

Modifier and Type	Field	Description
protected static final String	DEDUPLICATION_COMPARE_ORDER
protected static final String	DEDUPLICATION_GROUP_MODE
protected static final Text	urlKey
protected static final Charset	UTF_8

Fields inherited from class org.apache.nutch.util.NutchTool

currentJob, currentJobNum, numJobs, results, status

Constructor Summary

Constructors

Constructor	Description
DeduplicationJob()

Method Summary

Modifier and Type	Method	Description
static void	main(String[] args)
int	run(String[] args)
Map<String,Object>	run(Map<String,Object> args, String crawlId)	Runs the tool, using a map of arguments.

Methods inherited from class org.apache.nutch.util.NutchTool

getProgress, getStatus, killJob, setConf, stopJob

Methods inherited from class org.apache.hadoop.conf.Configured

getConf

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.hadoop.conf.Configurable

getConf, setConf

Field Details

urlKey

protected static final Text urlKey

DEDUPLICATION_GROUP_MODE

protected static final String DEDUPLICATION_GROUP_MODE

See Also:

• Constant Field Values

DEDUPLICATION_COMPARE_ORDER

protected static final String DEDUPLICATION_COMPARE_ORDER

See Also:

• Constant Field Values

UTF_8

protected static final Charset UTF_8

Constructor Details

DeduplicationJob

public DeduplicationJob()

Method Details

run

public int run(String[] args)
        throws IOException

Specified by:

run in interface Tool

Throws:

IOException

main

public static void main(String[] args)
                 throws Exception

Throws:

Exception

run

public Map<String,Object> run(Map<String,Object> args,
 String crawlId)
                       throws Exception

Description copied from class: NutchTool

Runs the tool, using a map of arguments. May return results, or null.

Specified by:

run in class NutchTool

Parameters:

args - a Map of arguments to be run with the tool

crawlId - a crawl identifier to associate with the tool invocation

Returns:

Map results object if tool executes successfully otherwise null

Throws:

Exception - if there is an error during the tool execution