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/*
* Licensed to Elasticsearch 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.
*/
package org.elasticsearch.index.query;
import org.apache.lucene.queries.BoostingQuery;
import org.apache.lucene.search.Query;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.xcontent.XContentBuilder;
import java.io.IOException;
import java.util.Objects;
/**
* The BoostingQuery class can be used to effectively demote results that match a given query.
* Unlike the "NOT" clause, this still selects documents that contain undesirable terms,
* but reduces their overall score:
* <p>
* Query balancedQuery = new BoostingQuery(positiveQuery, negativeQuery, 0.01f);
* In this scenario the positiveQuery contains the mandatory, desirable criteria which is used to
* select all matching documents, and the negativeQuery contains the undesirable elements which
* are simply used to lessen the scores. Documents that match the negativeQuery have their score
* multiplied by the supplied "boost" parameter, so this should be less than 1 to achieve a
* demoting effect
*/
public class BoostingQueryBuilder extends AbstractQueryBuilder<BoostingQueryBuilder> {
public static final String NAME = "boosting";
private final QueryBuilder positiveQuery;
private final QueryBuilder negativeQuery;
private float negativeBoost = -1;
static final BoostingQueryBuilder PROTOTYPE = new BoostingQueryBuilder(EmptyQueryBuilder.PROTOTYPE, EmptyQueryBuilder.PROTOTYPE);
/**
* Create a new {@link BoostingQueryBuilder}
*
* @param positiveQuery the positive query for this boosting query.
* @param negativeQuery the negative query for this boosting query.
*/
public BoostingQueryBuilder(QueryBuilder positiveQuery, QueryBuilder negativeQuery) {
if (positiveQuery == null) {
throw new IllegalArgumentException("inner clause [positive] cannot be null.");
}
if (negativeQuery == null) {
throw new IllegalArgumentException("inner clause [negative] cannot be null.");
}
this.positiveQuery = positiveQuery;
this.negativeQuery = negativeQuery;
}
/**
* Get the positive query for this boosting query.
*/
public QueryBuilder positiveQuery() {
return this.positiveQuery;
}
/**
* Get the negative query for this boosting query.
*/
public QueryBuilder negativeQuery() {
return this.negativeQuery;
}
/**
* Set the negative boost factor.
*/
public BoostingQueryBuilder negativeBoost(float negativeBoost) {
if (negativeBoost < 0) {
throw new IllegalArgumentException("query requires negativeBoost to be set to positive value");
}
this.negativeBoost = negativeBoost;
return this;
}
/**
* Get the negative boost factor.
*/
public float negativeBoost() {
return this.negativeBoost;
}
@Override
protected void doXContent(XContentBuilder builder, Params params) throws IOException {
builder.startObject(NAME);
builder.field(BoostingQueryParser.POSITIVE_FIELD.getPreferredName());
positiveQuery.toXContent(builder, params);
builder.field(BoostingQueryParser.NEGATIVE_FIELD.getPreferredName());
negativeQuery.toXContent(builder, params);
builder.field(BoostingQueryParser.NEGATIVE_BOOST_FIELD.getPreferredName(), negativeBoost);
printBoostAndQueryName(builder);
builder.endObject();
}
@Override
public String getWriteableName() {
return NAME;
}
@Override
protected Query doToQuery(QueryShardContext context) throws IOException {
Query positive = positiveQuery.toQuery(context);
Query negative = negativeQuery.toQuery(context);
// make upstream queries ignore this query by returning `null`
// if either inner query builder returns null
if (positive == null || negative == null) {
return null;
}
return new BoostingQuery(positive, negative, negativeBoost);
}
@Override
protected int doHashCode() {
return Objects.hash(negativeBoost, positiveQuery, negativeQuery);
}
@Override
protected boolean doEquals(BoostingQueryBuilder other) {
return Objects.equals(negativeBoost, other.negativeBoost) &&
Objects.equals(positiveQuery, other.positiveQuery) &&
Objects.equals(negativeQuery, other.negativeQuery);
}
@Override
protected BoostingQueryBuilder doReadFrom(StreamInput in) throws IOException {
QueryBuilder positiveQuery = in.readQuery();
QueryBuilder negativeQuery = in.readQuery();
BoostingQueryBuilder boostingQuery = new BoostingQueryBuilder(positiveQuery, negativeQuery);
boostingQuery.negativeBoost = in.readFloat();
return boostingQuery;
}
@Override
protected void doWriteTo(StreamOutput out) throws IOException {
out.writeQuery(positiveQuery);
out.writeQuery(negativeQuery);
out.writeFloat(negativeBoost);
}
}
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