org.elasticsearch.search.rescore.Rescorer Maven / Gradle / Ivy
package org.elasticsearch.search.rescore;
/*
* Licensed to ElasticSearch and Shay Banon under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. ElasticSearch 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 java.io.IOException;
import java.util.Set;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.Explanation;
import org.apache.lucene.search.TopDocs;
import org.elasticsearch.action.search.SearchType;
import org.elasticsearch.common.xcontent.XContentParser;
import org.elasticsearch.search.internal.SearchContext;
/**
* A query rescorer interface used to re-rank the Top-K results of a previously
* executed search.
*/
public interface Rescorer {
/**
* Returns the name of this rescorer
*/
public String name();
/**
* Modifies the result of the previously executed search ({@link TopDocs})
* in place based on the given {@link RescoreSearchContext}.
*
* @param topDocs the result of the previously exectued search
* @param context the current {@link SearchContext}. This will never be null.
* @param rescoreContext the {@link RescoreSearchContext}. This will never be null
* @throws IOException if an {@link IOException} occurs during rescoring
*/
public void rescore(TopDocs topDocs, SearchContext context, RescoreSearchContext rescoreContext) throws IOException;
/**
* Executes an {@link Explanation} phase on the rescorer.
* @param topLevelDocId the global / top-level document ID to explain
* @param context the current {@link SearchContext}
* @param rescoreContext TODO
* @return the explain for the given top level document ID.
* @throws IOException if an {@link IOException} occurs
*/
public Explanation explain(int topLevelDocId, SearchContext context, RescoreSearchContext rescoreContext) throws IOException;
/**
* Parses the {@link RescoreSearchContext} for this impelementation
* @param parser the parser to read the context from
* @param context the current search context
* @return the parsed {@link RescoreSearchContext}
* @throws IOException if an {@link IOException} occurs while parsing the context
*/
public RescoreSearchContext parse(XContentParser parser, SearchContext context) throws IOException;
/**
* Extracts all terms needed to exectue this {@link Rescorer}. This method
* is executed in a distributed frequency collection roundtrip for
* {@link SearchType#DFS_QUERY_AND_FETCH} and
* {@link SearchType#DFS_QUERY_THEN_FETCH}
*/
public void extractTerms(SearchContext context, RescoreSearchContext rescoreContext, Set termsSet);
/*
* TODO: At this point we only have one implemenation which modifies the
* TopDocs given. Future implemenations might return actual resutls that
* contain information about the rescore context. For example a pair wise
* reranker might return the feature vector for the top N window in order to
* merge results on the callers side. For now we don't have a return type at
* all since something like this requires a more general refactoring how
* documents are merged since in such a case we don't really have a score
* per document rather a "X is more relevant than Y" relation
*/
}