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From JensBurkhardt <jensburkha...@web.de>
Subject Re: explain() - fieldnorm
Date Tue, 25 Mar 2008 16:10:41 GMT

another problem just occurred. These are the results from explain() :

0.27576536 = (MATCH) product of:
  0.827296 = (MATCH) sum of:
    0.827296 = (MATCH) sum of:
      0.24544832 = (MATCH) weight(ti:genetik in 1849319), product of:
        0.015469407 = queryWeight(ti:genetik), product of:
          10.577795 = idf(docFreq=270)
          0.0014624415 = queryNorm
        15.866693 = (MATCH) fieldWeight(ti:genetik in 1849319), product of:
          1.0 = tf(termFreq(ti:genetik)=1)
          10.577795 = idf(docFreq=270)
          1.5 = fieldNorm(field=ti, doc=1849319)
      0.58184767 = (MATCH) weight(au:knippers in 1849319), product of:
        0.020028148 = queryWeight(au:knippers), product of:
          13.695007 = idf(docFreq=11)
          0.0014624415 = queryNorm
        29.051497 = (MATCH) fieldWeight(au:knippers in 1849319), product of:
          1.4142135 = tf(termFreq(au:knippers)=2)
          13.695007 = idf(docFreq=11)
          1.5 = fieldNorm(field=au, doc=1849319)
  0.33333334 = coord(1/3)

0.27576536 = (MATCH) product of:
  0.827296 = (MATCH) sum of:
    0.827296 = (MATCH) sum of:
      0.24544832 = (MATCH) weight(ti:genetik in 3221603), product of:
        0.015469407 = queryWeight(ti:genetik), product of:
          10.577795 = idf(docFreq=270)
          0.0014624415 = queryNorm
        15.866693 = (MATCH) fieldWeight(ti:genetik in 3221603), product of:
          1.0 = tf(termFreq(ti:genetik)=1)
          10.577795 = idf(docFreq=270)
          1.5 = fieldNorm(field=ti, doc=3221603)
      0.58184767 = (MATCH) weight(au:knippers in 3221603), product of:
        0.020028148 = queryWeight(au:knippers), product of:
          13.695007 = idf(docFreq=11)
          0.0014624415 = queryNorm
        29.051497 = (MATCH) fieldWeight(au:knippers in 3221603), product of:
          1.4142135 = tf(termFreq(au:knippers)=2)
          13.695007 = idf(docFreq=11)
          1.5 = fieldNorm(field=au, doc=3221603)
  0.33333334 = coord(1/3)

As you can see, both are exactly the same. The thing i don't understand is,
that the two documents have different documentboosts (the first one got an
boost of 1.62 , the second of 1.65) - the boosts are different because the
two books got different publication years - but explain() tells me that my
fieldNorm value is 1.5.
While indexing i use a new similarity class where lengthNorm just returns 1,
so the field length does not matter anymore.

Best Regards 

Jens Burkhardt


hossman wrote:
> 
> : As my subject is telling, i have a little problem with analyzing the
> : explain() output.
> : I know, that the fieldnorm value consists out of "documentboost,
> fieldboost
> : and lengthNorm". 
> : Is is possible to recieve the single values? I know that they are
> multiplied
> : while indexing but
> : can they be stored so that i can read them when i analyze my search?
> 
> the number of terms the docs have in a given field can be determined by 
> doing a nested iteration over a TermEnum and TermDoc and keeping count, 
> but there is no way to keep extract the document boost vs the field boost 
> -- if you want to know what those were later you have to store them 
> yourselves (in a stored field perhaps).
> 
> : The Problem is, that i have 2 Documents I want to compare but the only
> : difference is the fieldnorm value
> : and i don't know which value exactly makes this difference.
> 
> typically the answer to that question for me is "length" because i don't 
> use field boosts and doc boosts -- if you *do* use field boosts or doc 
> boosts, you would typically know what you had, and could check what boost 
> values you had used later (based on whatever source you orriginally built 
> your index from)
> 
> 
> 
> 
> -Hoss
> 
> 
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