/**
* 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.
*/
package org.apache.lucene.search.function;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.FieldCache;
import java.io.IOException;
/**
* Expert: obtains the ordinal of the field value from the default Lucene
* {@link org.apache.lucene.search.FieldCache FieldCache} using getStringIndex()
* and reverses the order.
* <p>
* The native lucene index order is used to assign an ordinal value for each field value.
* <p>
* Field values (terms) are lexicographically ordered by unicode value, and numbered starting at 1.
* <br>
* Example of reverse ordinal (rord):
* <br>If there were only three field values: "apple","banana","pear"
* <br>then rord("apple")=3, rord("banana")=2, ord("pear")=1
* <p>
* WARNING:
* rord() depends on the position in an index and can thus change
* when other documents are inserted or deleted,
* or if a MultiSearcher is used.
*
* <p><font color="#FF0000">
* WARNING: The status of the <b>search.function</b> package is experimental.
* The APIs introduced here might change in the future and will not be
* supported anymore in such a case.</font>
*
* @author yonik
*/
public class ReverseOrdFieldSource extends ValueSource {
public String field;
/**
* Contructor for a certain field.
* @param field field whose values reverse order is used.
*/
public ReverseOrdFieldSource(String field) {
this.field = field;
}
/*(non-Javadoc) @see org.apache.lucene.search.function.ValueSource#description() */
public String description() {
return "rord("+field+')';
}
/*(non-Javadoc) @see org.apache.lucene.search.function.ValueSource#getValues(org.apache.lucene.index.IndexReader) */
public DocValues getValues(IndexReader reader) throws IOException {
final FieldCache.StringIndex sindex = FieldCache.DEFAULT.getStringIndex(reader, field);
final int arr[] = sindex.order;
final int end = sindex.lookup.length;
return new DocValues(arr.length) {
/*(non-Javadoc) @see org.apache.lucene.search.function.DocValues#floatVal(int) */
public float floatVal(int doc) {
return (float)(end - arr[doc]);
}
/* (non-Javadoc) @see org.apache.lucene.search.function.DocValues#intVal(int) */
public int intVal(int doc) {
return end - arr[doc];
}
/* (non-Javadoc) @see org.apache.lucene.search.function.DocValues#strVal(int) */
public String strVal(int doc) {
// the string value of the ordinal, not the string itself
return Integer.toString(intVal(doc));
}
/*(non-Javadoc) @see org.apache.lucene.search.function.DocValues#toString(int) */
public String toString(int doc) {
return description() + '=' + strVal(doc);
}
/*(non-Javadoc) @see org.apache.lucene.search.function.DocValues#getInnerArray() */
Object getInnerArray() {
return arr;
}
};
}
/*(non-Javadoc) @see java.lang.Object#equals(java.lang.Object) */
public boolean equals(Object o) {
if (o.getClass() != ReverseOrdFieldSource.class) return false;
ReverseOrdFieldSource other = (ReverseOrdFieldSource)o;
return this.field.equals(other.field);
}
private static final int hcode = ReverseOrdFieldSource.class.hashCode();
/*(non-Javadoc) @see java.lang.Object#hashCode() */
public int hashCode() {
return hcode + field.hashCode();
}
}
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