1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with this
4 * work for additional information regarding copyright ownership. The ASF
5 * licenses this file to you under the Apache License, Version 2.0 (the
6 * "License"); you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
13 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
14 * License for the specific language governing permissions and limitations
15 * under the License.
16 */
17 package org.apache.hadoop.hbase.io.hfile;
18
19 import java.io.IOException;
20 import java.nio.ByteBuffer;
21
22 import org.apache.hadoop.hbase.io.encoding.DataBlockEncoding;
23 import org.apache.hadoop.hbase.util.Bytes;
24 import org.apache.hadoop.hbase.util.Pair;
25
26 /**
27 * Controls what kind of data block encoding is used. If data block encoding is
28 * not set or the given block is not a data block (encoded or not), methods
29 * should just return the unmodified block.
30 */
31 public interface HFileDataBlockEncoder {
32 /** Type of encoding used for data blocks in HFile. Stored in file info. */
33 public static final byte[] DATA_BLOCK_ENCODING = Bytes.toBytes("DATA_BLOCK_ENCODING");
34
35 /**
36 * Converts a block from the on-disk format to the in-cache format. Called in
37 * the following cases:
38 * <ul>
39 * <li>After an encoded or unencoded data block is read from disk, but before
40 * it is put into the cache.</li>
41 * <li>To convert brand-new blocks to the in-cache format when doing
42 * cache-on-write.</li>
43 * </ul>
44 * @param block a block in an on-disk format (read from HFile or freshly
45 * generated).
46 * @return non null block which is coded according to the settings.
47 */
48 public HFileBlock diskToCacheFormat(HFileBlock block,
49 boolean isCompaction);
50
51 /**
52 * Should be called before an encoded or unencoded data block is written to
53 * disk.
54 * @param in KeyValues next to each other
55 * @param dummyHeader A dummy header to be written as a placeholder
56 * @return a non-null on-heap buffer containing the contents of the
57 * HFileBlock with unfilled header and block type
58 */
59 public Pair<ByteBuffer, BlockType> beforeWriteToDisk(
60 ByteBuffer in, boolean includesMemstoreTS, byte[] dummyHeader);
61
62 /**
63 * Decides whether we should use a scanner over encoded blocks.
64 * @param isCompaction whether we are in a compaction.
65 * @return Whether to use encoded scanner.
66 */
67 public boolean useEncodedScanner(boolean isCompaction);
68
69 /**
70 * Save metadata in HFile which will be written to disk
71 * @param writer writer for a given HFile
72 * @exception IOException on disk problems
73 */
74 public void saveMetadata(HFile.Writer writer) throws IOException;
75
76 /** @return the on-disk data block encoding */
77 public DataBlockEncoding getEncodingOnDisk();
78
79 /** @return the preferred in-cache data block encoding for normal reads */
80 public DataBlockEncoding getEncodingInCache();
81
82 /**
83 * @return the effective in-cache data block encoding, taking into account
84 * whether we are doing a compaction.
85 */
86 public DataBlockEncoding getEffectiveEncodingInCache(boolean isCompaction);
87
88 }