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.client;
20
21 import org.apache.hadoop.hbase.classification.InterfaceAudience;
22 import org.apache.hadoop.hbase.classification.InterfaceStability;
23 import org.apache.hadoop.hbase.client.metrics.ScanMetrics;
24
25 import java.io.Closeable;
26 import java.io.IOException;
27
28 /**
29 * Interface for client-side scanning.
30 * Go to {@link Table} to obtain instances.
31 */
32 @InterfaceAudience.Public
33 @InterfaceStability.Stable
34 public interface ResultScanner extends Closeable, Iterable<Result> {
35
36 /**
37 * Grab the next row's worth of values. The scanner will return a Result.
38 * @return Result object if there is another row, null if the scanner is
39 * exhausted.
40 * @throws IOException e
41 */
42 Result next() throws IOException;
43
44 /**
45 * @param nbRows number of rows to return
46 * @return Between zero and nbRows results
47 * @throws IOException e
48 */
49 Result[] next(int nbRows) throws IOException;
50
51 /**
52 * Closes the scanner and releases any resources it has allocated
53 */
54 @Override
55 void close();
56
57 /**
58 * Allow the client to renew the scanner's lease on the server.
59 * @return true if the lease was successfully renewed, false otherwise.
60 */
61 boolean renewLease();
62
63 /**
64 * @return the scan metrics, or {@code null} if we do not enable metrics.
65 */
66 ScanMetrics getScanMetrics();
67 }