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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.
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  package org.apache.hadoop.hbase.regionserver;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Random;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.CellUtil;
  import org.apache.hadoop.hbase.HBaseTestCase;
  import org.apache.hadoop.hbase.HColumnDescriptor;
  import org.apache.hadoop.hbase.HTableDescriptor;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.client.Durability;
  import org.apache.hadoop.hbase.client.Put;
  import org.apache.hadoop.hbase.client.Scan;
  import org.apache.hadoop.hbase.testclassification.SmallTests;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.junit.experimental.categories.Category;
  
  @Category(SmallTests.class)
  public class TestWideScanner extends HBaseTestCase {
    private static final Log LOG = LogFactory.getLog(TestWideScanner.class);
  
    static final byte[] A = Bytes.toBytes("A");
    static final byte[] B = Bytes.toBytes("B");
    static final byte[] C = Bytes.toBytes("C");
    static byte[][] COLUMNS = { A, B, C };
    static final Random rng = new Random();
    static final HTableDescriptor TESTTABLEDESC =
      new HTableDescriptor(TableName.valueOf("testwidescan"));
    static {
      for (byte[] cfName : new byte[][] { A, B, C }) {
        TESTTABLEDESC.addFamily(new HColumnDescriptor(cfName)
            // Keep versions to help debugging.
            .setMaxVersions(100)
            .setBlocksize(8 * 1024)
        );
      }
    }
  
    /** HRegionInfo for root region */
    HRegion r;
  
    private int addWideContent(HRegion region) throws IOException {
      int count = 0;
      for (char c = 'a'; c <= 'c'; c++) {
        byte[] row = Bytes.toBytes("ab" + c);
        int i, j;
        long ts = System.currentTimeMillis();
        for (i = 0; i < 100; i++) {
          byte[] b = Bytes.toBytes(String.format("%10d", i));
          for (j = 0; j < 100; j++) {
            Put put = new Put(row);
            put.setDurability(Durability.SKIP_WAL);
            put.add(COLUMNS[rng.nextInt(COLUMNS.length)], b, ++ts, b);
            region.put(put);
            count++;
          }
        }
      }
      return count;
    }
  
    public void testWideScanBatching() throws IOException {
      final int batch = 256;
      try {
        this.r = createNewHRegion(TESTTABLEDESC, null, null);
        int inserted = addWideContent(this.r);
        List<Cell> results = new ArrayList<Cell>();
        Scan scan = new Scan();
        scan.addFamily(A);
        scan.addFamily(B);
        scan.addFamily(C);
        scan.setMaxVersions(100);
        scan.setBatch(batch);
       InternalScanner s = r.getScanner(scan);
       int total = 0;
       int i = 0;
       boolean more;
       do {
         more = s.next(results);
         i++;
         LOG.info("iteration #" + i + ", results.size=" + results.size());
 
         // assert that the result set is no larger
         assertTrue(results.size() <= batch);
 
         total += results.size();
 
         if (results.size() > 0) {
           // assert that all results are from the same row
           byte[] row = CellUtil.cloneRow(results.get(0));
           for (Cell kv: results) {
             assertTrue(Bytes.equals(row, CellUtil.cloneRow(kv)));
           }
         }
 
         results.clear();
 
         // trigger ChangedReadersObservers
         Iterator<KeyValueScanner> scanners =
           ((HRegion.RegionScannerImpl)s).storeHeap.getHeap().iterator();
         while (scanners.hasNext()) {
           StoreScanner ss = (StoreScanner)scanners.next();
           ss.updateReaders(Collections.EMPTY_LIST, Collections.EMPTY_LIST);
         }
       } while (more);
 
       // assert that the scanner returned all values
       LOG.info("inserted " + inserted + ", scanned " + total);
       assertEquals(total, inserted);
 
       s.close();
     } finally {
       HRegion.closeHRegion(this.r);
     }
   }
 
 }