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From "Sebastian Nagel (JIRA)" <>
Subject [jira] [Commented] (NUTCH-656) DeleteDuplicates based on crawlDB only
Date Thu, 14 Nov 2013 22:19:23 GMT


Sebastian Nagel commented on NUTCH-656:

Well done! Run successful test crawl with deduplication.
One last remark: the dedup command is missing in command-line help of bin/nutch :)

> DeleteDuplicates based on crawlDB only 
> ---------------------------------------
>                 Key: NUTCH-656
>                 URL:
>             Project: Nutch
>          Issue Type: Wish
>          Components: indexer
>            Reporter: Julien Nioche
>            Assignee: Julien Nioche
>         Attachments: NUTCH-656.patch, NUTCH-656.v2.patch, NUTCH-656.v3.patch
> The existing dedup functionality relies on Lucene indices and can't be used when the
indexing is delegated to SOLR.
> I was wondering whether we could use the information from the crawlDB instead to detect
URLs to delete then do the deletions in an indexer-neutral way. As far as I understand the
content of the crawlDB contains all the elements we need for dedup, namely :
> * URL 
> * signature
> * fetch time
> * score
> In map-reduce terms we would have two different jobs : 
> * read crawlDB and compare on URLs : keep only most recent element - oldest are stored
in a file and will be deleted later
> * read crawlDB and have a map function generating signatures as keys and URL + fetch
time +score as value
> * reduce function would depend on which parameter is set (i.e. use signature or score)
and would output as list of URLs to delete
> This assumes that we can then use the URLs to identify documents in the indices.
> Any thoughts on this? Am I missing something?
> Julien

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