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59 lines
1.7 KiB
C++
59 lines
1.7 KiB
C++
#pragma once
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#include <memory>
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#include <time.h>
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#include <IO/ReadBufferFromFileBase.h>
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#include "CompressedReadBufferBase.h"
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#include <IO/UncompressedCache.h>
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#include <port/clock.h>
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namespace DB
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{
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/** A buffer for reading from a compressed file using the cache of decompressed blocks.
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* The external cache is passed as an argument to the constructor.
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* Allows you to increase performance in cases where the same blocks are often read.
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* Disadvantages:
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* - in case you need to read a lot of data in a row, but of them only a part is cached, you have to do seek-and.
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*/
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class CachedCompressedReadBuffer : public CompressedReadBufferBase, public ReadBuffer
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{
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private:
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const std::string path;
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UncompressedCache * cache;
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size_t buf_size;
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size_t estimated_size;
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size_t aio_threshold;
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std::unique_ptr<ReadBufferFromFileBase> file_in;
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size_t file_pos;
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/// A piece of data from the cache, or a piece of read data that we put into the cache.
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UncompressedCache::MappedPtr owned_cell;
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void initInput();
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bool nextImpl() override;
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/// Passed into file_in.
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ReadBufferFromFileBase::ProfileCallback profile_callback;
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clockid_t clock_type {};
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public:
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CachedCompressedReadBuffer(
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const std::string & path_, UncompressedCache * cache_, size_t estimated_size_, size_t aio_threshold_,
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size_t buf_size_ = DBMS_DEFAULT_BUFFER_SIZE);
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void seek(size_t offset_in_compressed_file, size_t offset_in_decompressed_block);
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void setProfileCallback(const ReadBufferFromFileBase::ProfileCallback & profile_callback_, clockid_t clock_type_ = CLOCK_MONOTONIC_COARSE)
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{
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profile_callback = profile_callback_;
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clock_type = clock_type_;
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}
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};
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}
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