Lucene.Net  3.0.3
Lucene.Net is a .NET port of the Java Lucene Indexing Library
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FieldScoreQuery.cs File Reference

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class  Lucene.Net.Search.Function.FieldScoreQuery
 A query that scores each document as the value of the numeric input field. The query matches all documents, and scores each document according to the numeric value of that field. It is assumed, and expected, that:

  • The field used here is indexed, and has exactly one token in every scored document.
  • Best if this field is un_tokenized.
  • That token is parsable to the selected type.
Combining this query in a FunctionQuery allows much freedom in affecting document scores. Note, that with this freedom comes responsibility: it is more than likely that the default Lucene scoring is superior in quality to scoring modified as explained here. However, in some cases, and certainly for research experiments, this capability may turn useful. When contructing this query, select the appropriate type. That type should match the data stored in the field. So in fact the "right" type should be selected before indexing. Type selection has effect on the RAM usage:

Caching: Values for the numeric field are loaded once and cached in memory for further use with the same IndexReader. To take advantage of this, it is extremely important to reuse index-readers or index-searchers, otherwise, for instance if for each query a new index reader is opened, large penalties would be paid for loading the field values into memory over and over again! More...
class  Lucene.Net.Search.Function.FieldScoreQuery.Type
 Type of score field, indicating how field values are interpreted/parsed. The type selected at search search time should match the data stored in the field. Different types have different RAM requirements:

  • BYTE consumes 1 * maxDocs bytes.
  • SHORT consumes 2 * maxDocs bytes.
  • INT consumes 4 * maxDocs bytes.
  • FLOAT consumes 8 * maxDocs bytes.


package  Lucene.Net.Search.Function