ClickHouse/dbms/IO/createReadBufferFromFileBase.cpp

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#include <IO/createReadBufferFromFileBase.h>
#include <IO/ReadBufferFromFile.h>
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#if defined(__linux__) || defined(__FreeBSD__)
#include <IO/ReadBufferAIO.h>
#endif
#include <IO/MMapReadBufferFromFile.h>
#include <Common/ProfileEvents.h>
namespace ProfileEvents
{
extern const Event CreatedReadBufferOrdinary;
extern const Event CreatedReadBufferAIO;
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extern const Event CreatedReadBufferAIOFailed;
extern const Event CreatedReadBufferMMap;
extern const Event CreatedReadBufferMMapFailed;
}
namespace DB
{
std::unique_ptr<ReadBufferFromFileBase> createReadBufferFromFileBase(
const std::string & filename_,
size_t estimated_size, size_t aio_threshold, size_t mmap_threshold,
size_t buffer_size_, int flags_, char * existing_memory_, size_t alignment)
{
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#if defined(__linux__) || defined(__FreeBSD__)
if (aio_threshold && estimated_size >= aio_threshold)
{
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/// Attempt to open a file with O_DIRECT
try
{
auto res = std::make_unique<ReadBufferAIO>(filename_, buffer_size_, flags_, existing_memory_);
ProfileEvents::increment(ProfileEvents::CreatedReadBufferAIO);
return res;
}
catch (const ErrnoException &)
{
/// Fallback to cached IO if O_DIRECT is not supported.
ProfileEvents::increment(ProfileEvents::CreatedReadBufferAIOFailed);
}
}
#else
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(void)aio_threshold;
(void)estimated_size;
#endif
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if (!existing_memory_ && mmap_threshold && estimated_size >= mmap_threshold)
{
try
{
auto res = std::make_unique<MMapReadBufferFromFile>(filename_, 0);
ProfileEvents::increment(ProfileEvents::CreatedReadBufferMMap);
return res;
}
catch (const ErrnoException &)
{
/// Fallback if mmap is not supported (example: pipe).
ProfileEvents::increment(ProfileEvents::CreatedReadBufferMMapFailed);
}
}
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ProfileEvents::increment(ProfileEvents::CreatedReadBufferOrdinary);
return std::make_unique<ReadBufferFromFile>(filename_, buffer_size_, flags_, existing_memory_, alignment);
}
}