ClickHouse/dbms/IO/UncompressedCache.h
Ivan 97f2a2213e
Move all folders inside /dbms one level up (#9974)
* Move some code outside dbms/src folder
* Fix paths
2020-04-02 02:51:21 +03:00

83 lines
1.9 KiB
C++

#pragma once
#include <Common/LRUCache.h>
#include <Common/SipHash.h>
#include <Common/UInt128.h>
#include <Common/ProfileEvents.h>
#include <IO/BufferWithOwnMemory.h>
namespace ProfileEvents
{
extern const Event UncompressedCacheHits;
extern const Event UncompressedCacheMisses;
extern const Event UncompressedCacheWeightLost;
}
namespace DB
{
struct UncompressedCacheCell
{
Memory<> data;
size_t compressed_size;
UInt32 additional_bytes;
};
struct UncompressedSizeWeightFunction
{
size_t operator()(const UncompressedCacheCell & x) const
{
return x.data.size();
}
};
/** Cache of decompressed blocks for implementation of CachedCompressedReadBuffer. thread-safe.
*/
class UncompressedCache : public LRUCache<UInt128, UncompressedCacheCell, UInt128TrivialHash, UncompressedSizeWeightFunction>
{
private:
using Base = LRUCache<UInt128, UncompressedCacheCell, UInt128TrivialHash, UncompressedSizeWeightFunction>;
public:
UncompressedCache(size_t max_size_in_bytes)
: Base(max_size_in_bytes) {}
/// Calculate key from path to file and offset.
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(offset);
hash.get128(key.low, key.high);
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;
}
private:
void onRemoveOverflowWeightLoss(size_t weight_loss) override
{
ProfileEvents::increment(ProfileEvents::UncompressedCacheWeightLost, weight_loss);
}
};
using UncompressedCachePtr = std::shared_ptr<UncompressedCache>;
}