org.apache.druid.query.UnionQueryRunner.java Source code

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Here is the source code for org.apache.druid.query.UnionQueryRunner.java

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/*
 * 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.druid.query;

import com.google.common.base.Function;
import com.google.common.collect.Lists;
import org.apache.druid.java.util.common.guava.MergeSequence;
import org.apache.druid.java.util.common.guava.Sequence;
import org.apache.druid.java.util.common.guava.Sequences;

import java.util.Map;

public class UnionQueryRunner<T> implements QueryRunner<T> {
    private final QueryRunner<T> baseRunner;

    public UnionQueryRunner(QueryRunner<T> baseRunner) {
        this.baseRunner = baseRunner;
    }

    @Override
    public Sequence<T> run(final QueryPlus<T> queryPlus, final Map<String, Object> responseContext) {
        Query<T> query = queryPlus.getQuery();
        DataSource dataSource = query.getDataSource();
        if (dataSource instanceof UnionDataSource) {

            return new MergeSequence<>(query.getResultOrdering(),
                    Sequences.simple(Lists.transform(((UnionDataSource) dataSource).getDataSources(),
                            new Function<DataSource, Sequence<T>>() {
                                @Override
                                public Sequence<T> apply(DataSource singleSource) {
                                    return baseRunner.run(queryPlus.withQuery(query.withDataSource(singleSource)),
                                            responseContext);
                                }
                            })));
        } else {
            return baseRunner.run(queryPlus, responseContext);
        }
    }

}