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From Andrzej Bialecki ...@getopt.org>
Subject Re: Document boost, is it working?
Date Wed, 31 Oct 2007 08:12:42 GMT
Bruno Dery wrote:
> Thanks for the help, you're right your example works. However looking in
> Luke I also see only ones (1 1 1) as the document boost. 

Then perhaps this value should be removed from the Luke's display ... 
because it will always read 1, and it's a correct value (see below).

> 
> I imagine Luke use's Lucene's Document.getBoost() function. Shouldn't
> this be considered a bug, as I'd expect to retrieve the same boost
> number (or at least some factor of it) when I look at my documents once
> indexed? Or perhaps there is something I'm not understanding about this
> Document.getBoost function, normally you expect a getter to return you
> the exact value you entered with the setter.

Document.setBoost / getBoost is _only_ guaranteed to return the same 
value if a document is newly created, i.e. it hasn't been stored & 
retrieved. This is related to the way Lucene stores boost values in the 
index - in order to save storage space the boost value is never stored 
explicitly, instead during the storing process it's multiplied by every 
field's lengthNorm, and stored together as a single-byte float.

(Actually, it's a function of the current index format - perhaps in the 
future Lucene will be able to store these values separately using 
another type of storage. So far there was no pressing need to do this).

-- 
Best regards,
Andrzej Bialecki     <><
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