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A module that is everything required to understands Druid Segments

There is a newer version: 0.12.3

/*
 * Licensed to Metamarkets Group Inc. (Metamarkets) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Metamarkets 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 io.druid.query;

import com.google.common.collect.Ordering;
import com.metamx.common.guava.Sequence;
import com.metamx.common.guava.nary.BinaryFn;
import io.druid.common.guava.CombiningSequence;

import java.util.Map;

/**
 */
public abstract class ResultMergeQueryRunner extends BySegmentSkippingQueryRunner
{
  public ResultMergeQueryRunner(
      QueryRunner baseRunner
  )
  {
    super(baseRunner);
  }

  @Override
  public Sequence doRun(QueryRunner baseRunner, Query query, Map context)
  {
    return CombiningSequence.create(baseRunner.run(query, context), makeOrdering(query), createMergeFn(query));
  }

  protected abstract Ordering makeOrdering(Query query);

  protected abstract BinaryFn createMergeFn(Query query);
}