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.
*/
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.function.DocValues;
import java.io.IOException;
import java.io.Serializable;
/**
* Expert: source of values for basic function queries.
* <P>At its default/simplest form, values - one per doc - are used as the score of that doc.
* <P>Values are instantiated as
* {@link org.apache.lucene.search.function.DocValues DocValues} for a particular reader.
* <P>ValueSource implementations differ in RAM requirements: it would always be a factor
* of the number of documents, but for each document the number of bytes can be 1, 2, 4, or 8.
*
* @lucene.experimental
*
*
*/
public abstract class ValueSource implements Serializable {
/**
* Return the DocValues used by the function query.
* @param reader the IndexReader used to read these values.
* If any caching is involved, that caching would also be IndexReader based.
* @throws IOException for any error.
*/
public abstract DocValues getValues(IndexReader reader) throws IOException;
/**
* description of field, used in explain()
*/
public abstract String description();
/* (non-Javadoc) @see java.lang.Object#toString() */
@Override
public String toString() {
return description();
}
/**
* Needed for possible caching of query results - used by {@link ValueSourceQuery#equals(Object)}.
* @see Object#equals(Object)
*/
@Override
public abstract boolean equals(Object o);
/**
* Needed for possible caching of query results - used by {@link ValueSourceQuery#hashCode()}.
* @see Object#hashCode()
*/
@Override
public abstract int hashCode();
}