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https://issues.apache.org/jira/browse/NUTCH-1113?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13876036#comment-13876036
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Sebastian Nagel edited comment on NUTCH-1113 at 1/19/14 11:36 PM:
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If (re)indexing multiple segments also IndexerMapReduce should take care about
ordering of values: newer ones must overwrite older ones. But that's not done
explicitly - it's just implicitly assumed that later values are newer. But if
indexing is done segment by segment (in chronological order) this should be no
problem. See NUTCH-1617.
was (Author: wastl-nagel):
If (re)indexing multiple segments also IndexerMapReduce should take care about
ordering of values: newer ones must overwrite older ones. But that's not done
explicitly - it's just implicitly assumed that later values are newer. But if
indexing is done segment by segment (in chronological order) this should be no
problem.
> Merging segments causes URLs to vanish from crawldb/index?
> ----------------------------------------------------------
>
> Key: NUTCH-1113
> URL: https://issues.apache.org/jira/browse/NUTCH-1113
> Project: Nutch
> Issue Type: Bug
> Affects Versions: 1.3
> Reporter: Edward Drapkin
> Priority: Blocker
> Fix For: 1.9
>
> Attachments: NUTCH-1113-junit.patch, NUTCH-1113-junit.patch,
> NUTCH-1113-junit.patch, NUTCH-1113-junit.patch, NUTCH-1113-junit.patch,
> NUTCH-1113-trunk.patch, merged_segment_output.txt, unmerged_segment_output.txt
>
>
> When I run Nutch, I use the following steps:
> nutch inject crawldb/ url.txt
> repeated 3 times:
> nutch generate crawldb/ segments/ -normalize
> nutch fetch `ls -d segments/* | tail -1`
> nutch parse `ls -d segments/* | tail -1`
> nutch update crawldb `ls -d segments/* | tail -1`
> nutch mergesegs merged/ -dir segments/
> nutch invertlinks linkdb/ -dir merged/
> nutch index index/ crawldb/ linkdb/ -dir merged/ (I forward ported the lucene
> indexing code from Nutch 1.1).
> When I crawl with merging segments, I lose about 20% of the URLs that wind up
> in the index vs. when I crawl without merging the segments. Somehow the
> segment merger causes me to lose ~20% of my crawl database!
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