blob: cce9a8e671c6ebedb875dafaaa1bedbe5af697f4 (
plain) (
blame)
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
|
#pragma once
#include <memory>
#include <time.h>
#include <IO/ReadBufferFromFileBase.h>
#include "CompressedReadBufferBase.h"
#include <IO/UncompressedCache.h>
namespace DB
{
/** A buffer for reading from a compressed file using the cache of decompressed blocks.
* The external cache is passed as an argument to the constructor.
* Allows you to increase performance in cases where the same blocks are often read.
* Disadvantages:
* - in case you need to read a lot of data in a row, but some of them only a part is cached, you have to do seek-and.
*/
class CachedCompressedReadBuffer final : public CompressedReadBufferBase, public ReadBuffer
{
private:
std::function<std::unique_ptr<ReadBufferFromFileBase>()> file_in_creator;
UncompressedCache * cache;
std::unique_ptr<ReadBufferFromFileBase> file_in;
const std::string path;
/// Current position in file_in
size_t file_pos;
/// A piece of data from the cache, or a piece of read data that we put into the cache.
UncompressedCache::MappedPtr owned_cell;
void initInput();
bool nextImpl() override;
void prefetch(Priority priority) override;
/// Passed into file_in.
ReadBufferFromFileBase::ProfileCallback profile_callback;
clockid_t clock_type {};
/// Check comment in CompressedReadBuffer
/* size_t nextimpl_working_buffer_offset; */
public:
CachedCompressedReadBuffer(const std::string & path, std::function<std::unique_ptr<ReadBufferFromFileBase>()> file_in_creator, UncompressedCache * cache_, bool allow_different_codecs_ = false);
/// Seek is lazy. It doesn't move the position anywhere, just remember them and perform actual
/// seek inside nextImpl.
void seek(size_t offset_in_compressed_file, size_t offset_in_decompressed_block) override;
void setProfileCallback(const ReadBufferFromFileBase::ProfileCallback & profile_callback_, clockid_t clock_type_ = CLOCK_MONOTONIC_COARSE)
{
profile_callback = profile_callback_;
clock_type = clock_type_;
}
void setReadUntilPosition(size_t position) override
{
initInput();
file_in->setReadUntilPosition(position);
}
void setReadUntilEnd() override
{
initInput();
file_in->setReadUntilEnd();
}
};
}
|
