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From Grant Ingersoll <gsing...@apache.org>
Subject Re: constructing a mini-index with just the number of hits for a term
Date Sat, 15 Nov 2008 17:39:24 GMT
Can you share what the actual problem is that you are trying to  
solve?  It might help put things in context for me.  I'm guessing you  
are doing some type of co-occurrence analysis, but...

More below.

On Nov 13, 2008, at 11:08 AM, Sven wrote:

> First - I apologize for the double post on my earlier email.  The  
> first time I sent it I received an error message from support@magentanews.com 
>  saying that I should instead send email to java-user@meltwater.com  
> so I thought it did not go through.
> My question is this - is there a way to use the Lucene/Solr  
> infrastructure to create a mini-index that simply contains a lookup  
> table of terms and the number of times they have appeared?

This could be possible.  I think I would create documents with  
Index.ANALYZED, and Store.NO.  Then, you just need to use the TermEnum  
and TermDocs to access the information that you need.  In a sense, you  
are just creating the term dictionary.  You could also turn off  
storing of NORMS, which will save too.

>
> I do not need to record which documents have them nor do I need to  
> know where in the documents they appear.  There could be (and  
> probably will be) more than 2^32 terms, however.

2^32 unique terms or 2^32 total terms?

>  I'm not sure if that makes a difference to the Lucene backend, but  
> thought it might be relevant.
> This question coincides with my earlier question about counting the  
> times a given term is associated with another term.  I figure that  
> this would be more easily accomplished by making the mini-index  
> described above alongside the normal index when a document is  
> indexed.  For example, when scanning:
>
> Bravely bold Sir Robin, brought forth from Camelot.  He was not  
> afraid to die!  Oh, brave Sir Robin!
>
> In addition to the normal indexing function of Lucene, I would like  
> to write something on the backend to also index:
>
> bravely|bold
> bravely|sir
> bravely|robin
> bravely|brought
> bravely|forth
> bold|sir
> bold|robin
> bold|brought
> bold|forth
> bold|camelot  ("from" being a stop word)
> ...and so on
>
> I only need to keep a running total of each "bravely|bold" term,  
> however, since the number of terms will be quite large and keeping  
> track of the document/termpositions would translate to a lot of  
> wasted HD space.

For this, I think you will have to hook into the Analyzer process.   
The other thing to do is just try keeping the document/term positions,  
it may not actually be as bad as you think in terms of space.

>
> If such a thing is not already in place, could someone let me know  
> if there are some tutorials, documentation, or presentations that  
> describe the inner workings of Lucene and the theories/ 
> implementation at work for the actual file formats, structures, data  
> manipulations, etc?  (The javadocs don't go into this kind of  
> detail.)  I'm sure I can sift through the code and eventually make  
> sense of it, but if there is documentation out there, I'd prefer to  
> peruse that first.  My thought being that I can simply generate my  
> own kind of hash for each combined term and write it out to a custom  
> file structure similar to Lucene - but the specifics of how to  
> (optimally) do so are not plain to me yet.
> Thanks again!
> -Sven
>
>
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--------------------------
Grant Ingersoll

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