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https://issues.apache.org/jira/browse/NUTCH-2455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18051426#comment-18051426
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Lewis John McGibbney commented on NUTCH-2455:
---------------------------------------------
I took the liberty of changing this ticket title from
{quote}Speed up the merging of HostDb entries for variable fetch delay
{quote}
to
{quote}Use secondary sorting for memory-efficient HostDb integration in
Generator
{quote}
Having reviewed all of the commentary, patch and pull request I thought the
original title to be somewhat misleading because:
# "Speed up" implies execution time improvement, but the primary benefit is
memory efficiency
# "variable fetch delay" is just one feature—it also supports variable max
count per host
# It doesn't mention the key technique: secondary sorting
> Use secondary sorting for memory-efficient HostDb integration in Generator
> --------------------------------------------------------------------------
>
> 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
> Priority: Major
> Fix For: 1.22
>
> 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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