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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.search.Query;
import org.elasticsearch.action.support.ToXContentToBytes;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.xcontent.XContentBuilder;
import org.elasticsearch.common.xcontent.XContentType;
import java.io.IOException;
/**
* A {@link QueryBuilder} that is a stand in replacement for an empty query clause in the DSL.
* The current DSL allows parsing inner queries / filters like "{ }", in order to have a
* valid non-null representation of these clauses that actually do nothing we can use this class.
*
* This builder has no corresponding parser and it is not registered under the query name. It is
* intended to be used internally as a stand-in for nested queries that are left empty and should
* be ignored upstream.
*/
public class EmptyQueryBuilder extends ToXContentToBytes implements QueryBuilder<EmptyQueryBuilder> {
public static final String NAME = "empty_query";
/** the one and only empty query builder */
public static final EmptyQueryBuilder PROTOTYPE = new EmptyQueryBuilder();
// prevent instances other than prototype
private EmptyQueryBuilder() {
super(XContentType.JSON);
}
@Override
public String getWriteableName() {
return NAME;
}
@Override
public String getName() {
return getWriteableName();
}
@Override
public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
builder.startObject();
builder.endObject();
return builder;
}
@Override
public Query toQuery(QueryShardContext context) throws IOException {
// empty
return null;
}
@Override
public Query toFilter(QueryShardContext context) throws IOException {
// empty
return null;
}
@Override
public void writeTo(StreamOutput out) throws IOException {
}
@Override
public EmptyQueryBuilder readFrom(StreamInput in) throws IOException {
return EmptyQueryBuilder.PROTOTYPE;
}
@Override
public EmptyQueryBuilder queryName(String queryName) {
//no-op
return this;
}
@Override
public String queryName() {
return null;
}
@Override
public float boost() {
return -1;
}
@Override
public EmptyQueryBuilder boost(float boost) {
//no-op
return this;
}
}
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