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From Patrick Diviacco <patrick.divia...@gmail.com>
Subject Re: How to define different similarity scores per field ?
Date Tue, 01 Mar 2011 22:28:48 GMT
I see, but I don't get one thing... you are actually customizing only
normLenght method but not all the other methods that are calculating the
similarity scores...

those methods are called and they have the implementation you have in
DefaultSimilarityClass.. right ?



On 1 March 2011 21:12, Sujit Pal <sujit.pal@comcast.net> wrote:

> One way to do this currently is to build a per field similarity wrapper
> (that triggers off the field name). I believe there is some work going
> on with Lucene Similarity that would make it pluggable for this sort of
> stuff, but in the meantime, this is what I did:
>
> public class MyPerFieldSimilarityWrapper extends Similarity {
>
>  public MyPerFieldSimilarityWrapper() {
>    this.defaultSimilarity = new DefaultSimilarity();
>    this.fieldSimilarityMap = new HashMap<String,Similarity>();
>    this.fieldSimilarityMap.put("fieldA", new FieldASimilarity());
>    ...
>  }
>
>  @Override
>  public float lengthNorm(String fieldName, int numTokens) {
>    Similarity sim = fieldSimilarityMap.get(fieldName);
>    if (sim == null) {
>      return defaultSimilarity.lengthNorm(fieldName, numTokens);
>    } else {
>      return sim.lengthNorm(fieldName, numTokens);
>    }
>  }
>  // same for scorePayload. For the others, I just delegate
>  // to defaultSimilarity (all I really need is scorePayload in
>  // my case).
> }
>
> and in the schema.xml, I just set this class to be the similarity class:
>  <similarity class="com.mycompany.MyPerFieldSimilarityWrapper"/>
>
> hth
> -sujit
>
> On Tue, 2011-03-01 at 20:41 +0100, Patrick Diviacco wrote:
> > I need to define different similarity scores per document field.
> >
> > For example for field A I want to use Lucene tf.idf score, for the
> numerical
> > field B I want to use a different metric (difference between values) and
> so
> > on...
> >
> > thanks
>
>
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