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https://issues.apache.org/jira/browse/NUTCH-2455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16271137#comment-16271137
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Semyon Semyonov commented on NUTCH-2455:
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Thanks for the suggestion [~wastl-nagel]
The main question is : why not to change key of reducer to host instead?
Now I see that reducers reduce based on sorting value, but it never used in the
reducer itself.
output.collect(key, entry); is only call with the key.
Why not perform host parsing in the mapper and then reduce based on key(what
means all the values from the host go to the same reducer)?
> Speed up the merging of HostDb entries for variable fetch delay
> ---------------------------------------------------------------
>
> Key: NUTCH-2455
> URL: https://issues.apache.org/jira/browse/NUTCH-2455
> Project: Nutch
> Issue Type: Improvement
> Components: generator
> Affects Versions: 1.13
> Reporter: Markus Jelsma
> Attachments: NUTCH-2455.patch
>
>
> Citing Sebastian at NUTCH-2420:
> ??The correct solution would be to use <host,score> pairs as keys in the
> Selector job, with a partitioner and secondary sorting so that all keys with
> same host end up in the same call of the reducer. If values can also hold a
> HostDb entry and the sort comparator guarantees that the HostDb entry
> (entries if partitioned by domain or IP) comes in front of all CrawlDb
> entries. But that would be a substantial improvement...??
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