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From MitchK <>
Subject Solr and Nutch/Droids - to use or not to use?
Date Wed, 16 Jun 2010 15:27:20 GMT

Hello community, 

from several discussions about Solr and Nutch, I got some questions for a
virtual web-search-engine. 
I know I've posted this message to the mailing list a few days ago, but the
thread got injected and at least I did not get any more postings about the
topic and so I try to reopen it, hopefully no one gets upset here :-).
Please, bear with me. Thank you.

The requirements: 
I. I need a scalable solution for a growing index that becomes larger than
one machine can handle. If I add more hardware, I want to linear improve the

II. I want to use technologies like the OPIC-algorithm (default algorithm in
Nutch) or PageRank or... whatever is out there to improve the ranking of the

III. I want to be able to easily add more fields to my documents. Imagine
one retrives information from a webpage's content, than I want to make it

IV. While fetching my data, I want to make special-searches possible. For
example I want to retrive pictures from a webpage and want to index
picture-related content into another search-index plus I want to save a
small thumbnail of the picture itself. Btw: This is (as far as I know) not
possible with solr, because solr was not intended to do such special

V. I want to use filter queries (i.e. main-query "christopher lee" returns
1.5mio results, subquery "action" -> the main-query would be a filter-query
and "action" would be the actual query. So a search within search-results
would be easily made available). 

VI. I want to be able to use different logics for different pages. Maybe I
got a pool of 100 domains that I know better than others and I got special
scripts that retrive more special information from those 100 domains. Than I
want to apply my special logic to those 100 domains, but every other domain
should use the default logic. 


The project is only virtual. So why I am asking? 
I want to learn more about websearch and I would like to make some new

What do I know about Solr + Nutch: 
As it is said on, Solr + Nutch does not scale if the
index is too large. 
The article was a little bit older and I don't know whether this problem
gets fixed with the new distributed abilities of Solr. 

Furthermore I don't want to index the pages with nutch and reindex them with
The only exception would be: If the content of a webpage get's indexed by
nutch, I want to use the already tokenized content of the body with some
Solr copyfield operations to extend the search (i.e. making fuzzy search
possible). At the moment: I don't think this is possible. 

I don't know much about the droids project and how well it is documented. 
But from what I can read by some posts of Otis, it seems to be usable as a

Pros for Nutch are: It is very scalable! Thanks to hadoop and MapReduce it
is a scaling-monster (from what I've read). 

Cons: The search is not as rich as it is possible with Solr. Extend Nutch's
search-abilities *seems* to be more complicated than with Solr. Furthermore,
if I want to use Solr to search nutch's index, looking at my requirements I
would need to reindex the whole thing - without the benefits of Hadoop. 

What I don't know at the moment is, how it is possible to use algorithms
like in II. mentioned with Solr. 

I hope you understand the problem here - Solr *seems* to me as it would not
be the best solution for a web-search-engine, because of scaling reasons in

Where should I dive deeper? 
Solr + Droids? 
Solr + Nutch? 
Nutch + howToExtendNutchToMakeSearchBetter? 

Thanks for the discussion! 
- Mitch
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