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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.Lists;
import io.druid.query.aggregation.AggregatorFactory;

import java.nio.ByteBuffer;
import java.util.List;

/**
 */
public class QueryCacheHelper
{
  public static byte[] computeAggregatorBytes(List aggregatorSpecs)
  {
    List cacheKeySet = Lists.newArrayListWithCapacity(aggregatorSpecs.size());

    int totalSize = 0;
    for (AggregatorFactory spec : aggregatorSpecs) {
      final byte[] cacheKey = spec.getCacheKey();
      cacheKeySet.add(cacheKey);
      totalSize += cacheKey.length;
    }

    ByteBuffer retVal = ByteBuffer.allocate(totalSize);
    for (byte[] bytes : cacheKeySet) {
      retVal.put(bytes);
    }
    return retVal.array();
  }

}