content: package org.apache.lucene.search.function;
  
  /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  /**
   * A query that scores each document as the value of the numeric input field.
   * <p> 
   * The query matches all documents, and scores each document according to the numeric 
   * value of that field. 
   * <p>
   * It is assumed, and expected, that:
   * <ul>
   *  <li>The field used here is indexed, and has exactly 
   *      one token in every scored document.</li> 
   *  <li>Best if this field is un_tokenized.</li>
   *  <li>That token is parseable to the selected type.</li>
   * </ul>
   * <p>  
   * 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.
   * <p>
   * When constructing 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: 
   * <ul>
   *   <li>{@link Type#BYTE} consumes 1 * maxDocs bytes.</li>
   *   <li>{@link Type#SHORT} consumes 2 * maxDocs bytes.</li>
   *   <li>{@link Type#INT} consumes 4 * maxDocs bytes.</li>
   *   <li>{@link Type#FLOAT} consumes 8 * maxDocs bytes.</li>
   * </ul>
   * <p>
   * <b>Caching:</b>
   * 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!
   * 
   * @lucene.experimental
   */
  public class FieldScoreQuery extends ValueSourceQuery {
  
    /**
     * Type of score field, indicating how field values are interpreted/parsed.  
     * <p>
     * The type selected at search search time should match the data stored in the field. 
     * Different types have different RAM requirements: 
     * <ul>
     *   <li>{@link #BYTE} consumes 1 * maxDocs bytes.</li>
     *   <li>{@link #SHORT} consumes 2 * maxDocs bytes.</li>
     *   <li>{@link #INT} consumes 4 * maxDocs bytes.</li>
     *   <li>{@link #FLOAT} consumes 8 * maxDocs bytes.</li>
     * </ul>
     */
    public static class Type {
      
      /** field values are interpreted as numeric byte values. */
      public static final Type BYTE = new Type("byte"); 
  
      /** field values are interpreted as numeric short values. */
      public static final Type SHORT = new Type("short"); 
  
      /** field values are interpreted as numeric int values. */
      public static final Type INT = new Type("int"); 
  
      /** field values are interpreted as numeric float values. */
      public static final Type FLOAT = new Type("float"); 
  
      private String typeName;
      private Type (String name) {
        this.typeName = name;
      }
      /*(non-Javadoc) @see java.lang.Object#toString() */
      @Override
      public String toString() {
        return getClass().getName()+"::"+typeName;
      }
    }
    
    /**
     * Create a FieldScoreQuery - a query that scores each document as the value of the numeric input field.
     * <p>
     * The <code>type</code> param tells how to parse the field string values into a numeric score value.
     * @param field the numeric field to be used.
     * @param type the type of the field: either
     * {@link Type#BYTE}, {@link Type#SHORT}, {@link Type#INT}, or {@link Type#FLOAT}. 
     */
    public FieldScoreQuery(String field, Type type) {
      super(getValueSource(field,type));
    }
  
    // create the appropriate (cached) field value source.  
    private static ValueSource getValueSource(String field, Type type) {
      if (type == Type.BYTE) {
        return new ByteFieldSource(field);
      }
      if (type == Type.SHORT) {
        return new ShortFieldSource(field);
      }
      if (type == Type.INT) {
        return new IntFieldSource(field);
      }
      if (type == Type.FLOAT) {
        return new FloatFieldSource(field);
      }
      throw new IllegalArgumentException(type+" is not a known Field Score Query Type!");
    }
  
  }
  