org.apache.nutch.crawl

## Class CrawlDbMerger

- java.lang.Object
- - org.apache.hadoop.conf.Configured
  - - org.apache.nutch.crawl.CrawlDbMerger

- All Implemented Interfaces:
    Configurable, Tool

      public class CrawlDbMerger
      extends Configured
      implements Tool

  This tool merges several CrawlDb-s into one, optionally filtering URLs through the current URLFilters, to skip prohibited pages.

  It's possible to use this tool just for filtering - in that case only one CrawlDb should be specified in arguments.

  If more than one CrawlDb contains information about the same URL, only the most recent version is retained, as determined by the value of `CrawlDatum.getFetchTime()`. However, all metadata information from all versions is accumulated, with newer values taking precedence over older values.

  Author:
    Andrzej Bialecki

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `static class` | `CrawlDbMerger.Merger`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `CrawlDbMerger()`
    `CrawlDbMerger(Configuration conf)`

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `static Job` | `createMergeJob(Configuration conf, Path output, boolean normalize, boolean filter)`
    `static void` | `main(String[] args)`
    `void` | `merge(Path output, Path[] dbs, boolean normalize, boolean filter)`
    `int` | `run(String[] args)`

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

      `getConf, setConf`

    - ### 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`

- - ### Constructor Detail

    - #### CrawlDbMerger

          public CrawlDbMerger()

    - #### CrawlDbMerger

          public CrawlDbMerger(Configuration conf)

  - ### Method Detail

    - #### merge

          public void merge(Path output,
                            Path[] dbs,
                            boolean normalize,
                            boolean filter)
                     throws Exception

      Throws:
        `Exception`

    - #### createMergeJob

          public static Job createMergeJob(Configuration conf,
                                           Path output,
                                           boolean normalize,
                                           boolean filter)
                                    throws IOException

      Throws:
        `IOException`

    - #### main

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

      Parameters:
        `args` -
      Throws:
        `Exception`

    - #### run

          public int run(String[] args)
                  throws Exception

      Specified by:
        `run` in interface `Tool`
      Throws:
        `Exception`

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