ClickHouse/dbms/include/DB/Storages/MarkCache.h
2015-04-16 09:12:35 +03:00

87 lines
2.1 KiB
C++

#pragma once
#include <memory>
#include <DB/Common/LRUCache.h>
#include <DB/Common/ProfileEvents.h>
#include <DB/Common/SipHash.h>
#include <DB/Interpreters/AggregationCommon.h>
namespace DB
{
struct MarkInCompressedFile
{
size_t offset_in_compressed_file;
size_t offset_in_decompressed_block;
bool operator==(const MarkInCompressedFile & rhs) const
{
return std::forward_as_tuple(offset_in_compressed_file, offset_in_decompressed_block) ==
std::forward_as_tuple(rhs.offset_in_compressed_file, rhs.offset_in_decompressed_block);
}
bool operator!=(const MarkInCompressedFile & rhs) const
{
return !(*this == rhs);
}
String toString() const
{
return "(" + DB::toString(offset_in_compressed_file) + "," + DB::toString(offset_in_decompressed_block) + ")";
}
};
typedef std::vector<MarkInCompressedFile> MarksInCompressedFile;
/// Оценка количества байтов, занимаемых засечками в кеше.
struct MarksWeightFunction
{
size_t operator()(const MarksInCompressedFile & marks) const
{
/// Можно еще добавить порядка 100 байт на накладные расходы вектора и кеша.
return marks.size() * sizeof(MarkInCompressedFile);
}
};
/** Кэш засечек в столбце из StorageMergeTree.
*/
class MarkCache : public LRUCache<UInt128, MarksInCompressedFile, UInt128TrivialHash, MarksWeightFunction>
{
private:
typedef LRUCache<UInt128, MarksInCompressedFile, UInt128TrivialHash, MarksWeightFunction> Base;
public:
MarkCache(size_t max_size_in_bytes)
: Base(max_size_in_bytes) {}
/// Посчитать ключ от пути к файлу и смещения.
static UInt128 hash(const String & path_to_file)
{
UInt128 key;
SipHash hash;
hash.update(path_to_file.data(), path_to_file.size() + 1);
hash.get128(key.first, key.second);
return key;
}
MappedPtr get(const Key & key)
{
MappedPtr res = Base::get(key);
if (res)
ProfileEvents::increment(ProfileEvents::MarkCacheHits);
else
ProfileEvents::increment(ProfileEvents::MarkCacheMisses);
return res;
}
};
typedef std::shared_ptr<MarkCache> MarkCachePtr;
}