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From Ole-Martin Mørk <olemar...@gmail.com>
Subject Help understanding fieldNorm
Date Mon, 05 Oct 2009 08:21:19 GMT
Hi. I am trying to understand Lucene's scoring algorithm. We're
getting some strange results. First we search for a given page by it's
url. We get this result:

0.0014793393 = fieldWeight(url:"our super secret url" in 22), product of:
  1.0 = tf(phraseFreq=1.0)
  32.31666 = idf(url: www=7327 host=321 com=7327 article=2456
something=2 something=44 704290075=1)
  4.5776367E-5 = fieldNorm(field=url, doc=22)

When this is done, we use solrJ to read and write the document. The
only change is the title of the document (appends the number 2)

We search again and the fieldNorm is changed significantly:

9.874598 = fieldWeight(url:"our super secret url" in 0), product of:
  1.0 = tf(phraseFreq=1.0)
  31.598713 = idf(url: www=7328 host=322 com=7328 article=2457
something=3 somthing=45 704290075=2)
  0.3125 = fieldNorm(field=url, doc=0)

Why does the value of fieldNorm change so much?

Looking forward to your answers.

--
Ole-Martin Mørk
http://twitter.com/olemartin
http://flickr.com/olemartin

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