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 java.io.IOException;
23  import java.util.ArrayList;
24  import java.util.List;
25  
26  import org.apache.hadoop.hbase.KeyValue;
27  import org.apache.hadoop.hbase.client.Scan;
28  import org.apache.hadoop.hbase.regionserver.InternalScanner;
29  import org.apache.hadoop.hbase.util.Bytes;
30  
31  
32  /**
33   * The aggregation implementation at a region.
34   */
35  public class ColumnAggregationEndpoint extends BaseEndpointCoprocessor
36  implements ColumnAggregationProtocol {
37  
38    @Override
39    public long sum(byte[] family, byte[] qualifier)
40    throws IOException {
41      // aggregate at each region
42      Scan scan = new Scan();
43      scan.addColumn(family, qualifier);
44      int sumResult = 0;
45  
46      InternalScanner scanner = ((RegionCoprocessorEnvironment)getEnvironment())
47          .getRegion().getScanner(scan);
48      try {
49        List<KeyValue> curVals = new ArrayList<KeyValue>();
50        boolean done = false;
51        do {
52          curVals.clear();
53          done = scanner.next(curVals);
54          KeyValue kv = curVals.get(0);
55          sumResult += Bytes.toInt(kv.getBuffer(), kv.getValueOffset());
56        } while (done);
57      } finally {
58        scanner.close();
59      }
60      return sumResult;
61    }
62  }