1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
|
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#pragma once
#include "memory/memory_allocator.h"
#include "table/block_based/block.h"
#include "table/block_based/block_type.h"
#include "table/format.h"
namespace ROCKSDB_NAMESPACE {
// Retrieves a single block of a given file. Utilizes the prefetch buffer and/or
// persistent cache provided (if any) to try to avoid reading from the file
// directly. Note that both the prefetch buffer and the persistent cache are
// optional; also, note that the persistent cache may be configured to store either
// compressed or uncompressed blocks.
//
// If the retrieved block is compressed and the do_uncompress flag is set,
// BlockFetcher uncompresses the block (using the uncompression dictionary,
// if provided, to prime the compression algorithm), and returns the resulting
// uncompressed block data. Otherwise, it returns the original block.
//
// Two read options affect the behavior of BlockFetcher: if verify_checksums is
// true, the checksum of the (original) block is checked; if fill_cache is true,
// the block is added to the persistent cache if needed.
//
// Memory for uncompressed and compressed blocks is allocated as needed
// using memory_allocator and memory_allocator_compressed, respectively
// (if provided; otherwise, the default allocator is used).
class BlockFetcher {
public:
BlockFetcher(RandomAccessFileReader* file,
FilePrefetchBuffer* prefetch_buffer, const Footer& footer,
const ReadOptions& read_options, const BlockHandle& handle,
BlockContents* contents, const ImmutableCFOptions& ioptions,
bool do_uncompress, bool maybe_compressed, BlockType block_type,
const UncompressionDict& uncompression_dict,
const PersistentCacheOptions& cache_options,
MemoryAllocator* memory_allocator = nullptr,
MemoryAllocator* memory_allocator_compressed = nullptr,
bool for_compaction = false)
: file_(file),
prefetch_buffer_(prefetch_buffer),
footer_(footer),
read_options_(read_options),
handle_(handle),
contents_(contents),
ioptions_(ioptions),
do_uncompress_(do_uncompress),
maybe_compressed_(maybe_compressed),
block_type_(block_type),
uncompression_dict_(uncompression_dict),
cache_options_(cache_options),
memory_allocator_(memory_allocator),
memory_allocator_compressed_(memory_allocator_compressed),
for_compaction_(for_compaction) {}
Status ReadBlockContents();
CompressionType get_compression_type() const { return compression_type_; }
private:
static const uint32_t kDefaultStackBufferSize = 5000;
RandomAccessFileReader* file_;
FilePrefetchBuffer* prefetch_buffer_;
const Footer& footer_;
const ReadOptions read_options_;
const BlockHandle& handle_;
BlockContents* contents_;
const ImmutableCFOptions& ioptions_;
bool do_uncompress_;
bool maybe_compressed_;
BlockType block_type_;
const UncompressionDict& uncompression_dict_;
const PersistentCacheOptions& cache_options_;
MemoryAllocator* memory_allocator_;
MemoryAllocator* memory_allocator_compressed_;
Status status_;
Slice slice_;
char* used_buf_ = nullptr;
size_t block_size_;
CacheAllocationPtr heap_buf_;
CacheAllocationPtr compressed_buf_;
char stack_buf_[kDefaultStackBufferSize];
bool got_from_prefetch_buffer_ = false;
ROCKSDB_NAMESPACE::CompressionType compression_type_;
bool for_compaction_ = false;
// return true if found
bool TryGetUncompressBlockFromPersistentCache();
// return true if found
bool TryGetFromPrefetchBuffer();
bool TryGetCompressedBlockFromPersistentCache();
void PrepareBufferForBlockFromFile();
// Copy content from used_buf_ to new heap buffer.
void CopyBufferToHeap();
void GetBlockContents();
void InsertCompressedBlockToPersistentCacheIfNeeded();
void InsertUncompressedBlockToPersistentCacheIfNeeded();
void CheckBlockChecksum();
};
} // namespace ROCKSDB_NAMESPACE
|
