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From "Grant Ingersoll" <gsing...@syr.edu>
Subject Re: Term vectors: .tvf format question
Date Mon, 14 Jun 2004 18:20:45 GMT
Hey Erik,

The original code used ints to store the tv info.  Upon merging this into the latest code
base, it no longer worked b/c Lucene now uses longs for term info (if I recall correctly)
and this caused a problem on merging/optimization (at least with the old way of doing things.)
 After thinking about  alternatives, I chose the String implementation, as it allows term
vectors to be used in non-optimized indexes and the String is guaranteed to be unique w/in
the index, thus making optimization very easy.  Of course, there may be alternatives that
would allow one to use longs, I just didn't see one that was efficient, so I made the assumption
that disk space is cheap and went with it.

-Grant

>>> erik@ehatchersolutions.com 06/12/04 12:54PM >>>
I'm digging deeper into the Lucene index format to develop some higher 
level diagrams of its structure.   One thing that is curious to me is 
the term text being stored in the .tvf file.  Why not point to the term 
dictionary by position somehow and avoid duplicating this string, 
saving possibly substantial index size?  I'm assuming this is for 
performance reasons.

Note, the Lucene index file formats documentation needs to be updated - 
TermText is no longer just a String, it is a <PrefixLength,Suffix> 
similar to how terms in the .tis are stored.  I've updated 
fileformats.xml/.html - if I've gotten this wrong, let me know.

Just out of curiosity - are there any other known inconsistencies with 
the file formats documentation?  I'd be happy to fix them up if there 
are any other out of sync issues.  I just happened to spot the one just 
mentioned because I looked in the code to see how term vectors were 
written when I saw that the term text is duplicated.

	Erik


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