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https://issues.apache.org/jira/browse/NUTCH-656?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julien Nioche reopened NUTCH-656:
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Assignee: Julien Nioche
Am reopening this one as we need a generic deduplicator now that we have
committed NUTCH-1047. The SOLR dedup did work but was not very efficient as it
required pulling all the documents from SOLR and use them as an input to the
MapReduce code. The patch attached implements a generic deduplicator that can
be used with any indexing backend (e.g. elasticsearch, cloudsearch but also
solr). The main difference with the SOLR-specific code is that the score is the
one from the crawldb and not from the index and the entries are currently not
deleted from the crawldb, just in the index.
Andrzej's point about having duplicates entries in the segment is still
relevant but in practice documents with the same URLs (i.e. unique in the
crawldb) override each other when indexed so they are already deduped in a way.
> DeleteDuplicates based on crawlDB only
> ---------------------------------------
>
> Key: NUTCH-656
> URL: https://issues.apache.org/jira/browse/NUTCH-656
> Project: Nutch
> Issue Type: Wish
> Components: indexer
> Reporter: Julien Nioche
> Assignee: Julien Nioche
> Attachments: NUTCH-656.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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