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1   /**
2    *
3    * Licensed to the Apache Software Foundation (ASF) under one
4    * or more contributor license agreements.  See the NOTICE file
5    * distributed with this work for additional information
6    * regarding copyright ownership.  The ASF licenses this file
7    * to you under the Apache License, Version 2.0 (the
8    * "License"); you may not use this file except in compliance
9    * with the License.  You may obtain a copy of the License at
10   *
11   *     http://www.apache.org/licenses/LICENSE-2.0
12   *
13   * Unless required by applicable law or agreed to in writing, software
14   * distributed under the License is distributed on an "AS IS" BASIS,
15   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16   * See the License for the specific language governing permissions and
17   * limitations under the License.
18   */
19  package org.apache.hadoop.hbase.regionserver;
20  
21  import java.io.Closeable;
22  import java.io.IOException;
23  import java.util.List;
24  
25  import org.apache.hadoop.hbase.Cell;
26  import org.apache.hadoop.hbase.HBaseInterfaceAudience;
27  import org.apache.hadoop.hbase.classification.InterfaceAudience;
28  import org.apache.hadoop.hbase.classification.InterfaceStability;
29
30  /**
31   * Internal scanners differ from client-side scanners in that they operate on
32   * HStoreKeys and byte[] instead of RowResults. This is because they are
33   * actually close to how the data is physically stored, and therefore it is more
34   * convenient to interact with them that way. It is also much easier to merge
35   * the results across SortedMaps than RowResults.
36   *
37   * <p>Additionally, we need to be able to determine if the scanner is doing
38   * wildcard column matches (when only a column family is specified or if a
39   * column regex is specified) or if multiple members of the same column family
40   * were specified. If so, we need to ignore the timestamp to ensure that we get
41   * all the family members, as they may have been last updated at different
42   * times.
43   */
44  @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
45  @InterfaceStability.Evolving
46  public interface InternalScanner extends Closeable {
47    /**
48     * Grab the next row's worth of values.
49     * @param results return output array
50     * @return true if more rows exist after this one, false if scanner is done
51     * @throws IOException e
52     */
53    boolean next(List<Cell> results) throws IOException;
54
55    /**
56     * Grab the next row's worth of values.
57     * @param result return output array
58     * @param scannerContext
59     * @return true if more rows exist after this one, false if scanner is done
60     * @throws IOException e
61     */
62    boolean next(List<Cell> result, ScannerContext scannerContext) throws IOException;
63
64    /**
65     * Closes the scanner and releases any resources it has allocated
66     * @throws IOException
67     */
68    void close() throws IOException;
69  }