ClickHouse/dbms/include/DB/IO/UncompressedCache.h

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#pragma once
#include <DB/Common/LRUCache.h>
#include <DB/Common/SipHash.h>
#include <DB/Common/ProfileEvents.h>
#include <DB/IO/BufferWithOwnMemory.h>
#include <DB/Interpreters/AggregationCommon.h>
namespace DB
{
struct UncompressedCacheCell
{
Memory data;
size_t compressed_size;
};
/** Кэш разжатых блоков для CachedCompressedReadBuffer. thread-safe.
*/
class UncompressedCache : public LRUCache<UInt128, UncompressedCacheCell, UInt128TrivialHash>
{
private:
typedef LRUCache<UInt128, UncompressedCacheCell, UInt128TrivialHash> Base;
public:
UncompressedCache(size_t max_size_in_cells)
: Base(max_size_in_cells) {}
/// Посчитать ключ от пути к файлу и смещения.
static UInt128 hash(const String & path_to_file, size_t offset)
{
UInt128 key;
SipHash hash;
hash.update(path_to_file.data(), path_to_file.size() + 1);
hash.update(reinterpret_cast<const char *>(&offset), sizeof(offset));
hash.get128(key.first, key.second);
return key;
}
MappedPtr get(const Key & key)
{
MappedPtr res = Base::get(key);
if (res)
ProfileEvents::increment(ProfileEvents::UncompressedCacheHits);
else
ProfileEvents::increment(ProfileEvents::UncompressedCacheMisses);
return res;
}
};
typedef Poco::SharedPtr<UncompressedCache> UncompressedCachePtr;
}