: I would like to alter the similarity behaviour of solr to remove : the fieldnorm factor in the similarity calculations. As far as I : read, I need to recreate my own similarity class and import it into : solr using the <similarity> config in schema.xml. : : Has anybody already tweaked or played with this topic, and might : give me some code or advices ?
as you're already noticed, you can specify the Similarity class at runtime via the schema.xml -- the only Solr specific aspect of this making sure your Similarity class is in your servlet containers classpath (exactly how you do this depends on your servlet container) searching the java-dev and java-user Lucene mailing lists is the best bet for finding discussions on writing your own similarity, there are also some examples in the main Lucene code base... contrib/miscellaneous/src/java/org/apache/lucene/misc/SweetSpotSimilarity.java src/test/org/apache/lucene/search/TestDisjunctionMaxQuery.java ...if your main interest is just eliminating norms, there is a special option for that in Lucene Fields called "Omit Norms" (it not only eliminates the effects of norms on scoring, but it saves space in your index as well) in Solr you can turn it on/off per <field> or <fieldtype> using the omitNorms="true" option in the schema.xml -Hoss
