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72 lines
1.6 KiB
C++
72 lines
1.6 KiB
C++
#pragma once
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#include <memory>
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#include <DB/Common/LRUCache.h>
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#include <DB/Common/ProfileEvents.h>
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#include <DB/Common/SipHash.h>
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#include <DB/Interpreters/AggregationCommon.h>
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#include <DB/DataStreams/MarkInCompressedFile.h>
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namespace ProfileEvents
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{
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extern const Event MarkCacheHits;
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extern const Event MarkCacheMisses;
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}
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namespace DB
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{
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/// Estimate of number of bytes in cache for marks.
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struct MarksWeightFunction
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{
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size_t operator()(const MarksInCompressedFile & marks) const
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{
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/// NOTE Could add extra 100 bytes for overhead of std::vector, cache structures and allocator.
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return marks.size() * sizeof(MarkInCompressedFile);
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}
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};
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/** Cache of 'marks' for StorageMergeTree.
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* Marks is an index structure that addresses ranges in column file, corresponding to ranges of primary key.
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*/
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class MarkCache : public LRUCache<UInt128, MarksInCompressedFile, UInt128TrivialHash, MarksWeightFunction>
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{
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private:
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using Base = LRUCache<UInt128, MarksInCompressedFile, UInt128TrivialHash, MarksWeightFunction>;
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public:
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MarkCache(size_t max_size_in_bytes, const Delay & expiration_delay)
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: Base(max_size_in_bytes, expiration_delay) {}
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/// Calculate key from path to file and offset.
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static UInt128 hash(const String & path_to_file)
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{
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UInt128 key;
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SipHash hash;
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hash.update(path_to_file.data(), path_to_file.size() + 1);
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hash.get128(key.first, key.second);
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return key;
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}
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MappedPtr get(const Key & key)
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{
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MappedPtr res = Base::get(key);
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if (res)
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ProfileEvents::increment(ProfileEvents::MarkCacheHits);
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else
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ProfileEvents::increment(ProfileEvents::MarkCacheMisses);
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return res;
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}
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};
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using MarkCachePtr = std::shared_ptr<MarkCache>;
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}
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