Manoharam Reddy wrote:
> My segment merger is not functioning properly. I am unable to figure
> out the problem.
> 
> These are the commands I am using.
> 
> bin/nutch inject crawl/crawldb seedurls
> 
> In a loop iterating 10 times:-
> 
>  bin/nutch generate crawl/crawldb crawl/segments -topN 1000 -adddays 5
>  segment=`ls -d crawl/segments/* | tail -1`
>  bin/nutch fetch $segment -threads 50
>  bin/nutch updatedb crawl/crawldb $segment
> 
> After loop:-
> 
> bin/nutch mergesegs crawl/merged_segments crawl/segments/*
> rm -rf crawl/segments/*
> mv --verbose crawl/merged_segments/* crawl/segments
> rm -rf crawl/merged_segments
> 
> Merging 10 segments to crawl/MERGEDsegments/20050529095045
> SegmentMerger:   adding crawl/segments/20050528144604
> SegmentMerger:   adding crawl/segments/20050528144619
> SegmentMerger:   adding crawl/segments/20050528145426
> SegmentMerger:   adding crawl/segments/20050528151323
> SegmentMerger:   adding crawl/segments/20050528164032
> SegmentMerger:   adding crawl/segments/20050528170544
> SegmentMerger:   adding crawl/segments/20050528192341
> SegmentMerger:   adding crawl/segments/20050528203512
> SegmentMerger:   adding crawl/segments/20050528210029
> SegmentMerger:   adding crawl/segments/20050529055733
> SegmentMerger: using segment data from: crawl_generate
> `crawl/MERGEDsegments/20050529095045' -> `crawl/segments/20050529095045'
> 
> As can be seen here, only crawl_generate was used to merge. Other
> folders like parse_data, crawl_fetch were not used. Why?

This behavior is described in the javadoc of SegmentMerger. In general 
case, users may wish to merge segments at different stages of processing 
- only generated, fetched but not parsed, and parsed. It's easy to do 
this if segments are homogenous, i.e. they all contain the same parts.

However, if segments are heterogenous, i.e some of them are processed 
further than others, we cannot merge all their parts, because we will 
get an incomplete segment as a result (e.g for some urls we will have 
parse_data, for other urls it will be missing).

In such cases SegmentMerger processes only the lowest common 
denominator, i.e. only those segment parts that are present in all input 
segments - and disregards any other existing parts.

That's a long answer to your problem, which is that one or more of your 
input segments isn't fetched yet - don't include that segment on the 
list of input segments, and all should be fine.


-- 
Best regards,
Andrzej Bialecki     <><
  ___. ___ ___ ___ _ _   __________________________________
[__ || __|__/|__||\/|  Information Retrieval, Semantic Web
___|||__||  \|  ||  |  Embedded Unix, System Integration
http://www.sigram.com  Contact: info at sigram dot com


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