1   /*
2    * Copyright 2010 The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  package org.apache.hadoop.hbase.coprocessor;
21  
22  import org.apache.hadoop.hbase.ipc.CoprocessorProtocol;
23  import java.io.IOException;
24  
25  /**
26   * A sample protocol for performing aggregation at regions.
27   */
28  public interface ColumnAggregationProtocol extends CoprocessorProtocol {
29    /**
30     * Perform aggregation for a given column at the region. The aggregation
31     * will include all the rows inside the region. It can be extended to
32     * allow passing start and end rows for a fine-grained aggregation.
33     * @param family family
34     * @param qualifier qualifier
35     * @return Aggregation of the column.
36     * @throws exception.
37     */
38    public long sum(byte[] family, byte[] qualifier) throws IOException;
39  }