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#pragma once
#include <memory>
#include <mutex>
#include <Core/Types.h>
#include <Common/Exception.h>
#include <Interpreters/Cache/FileCacheKey.h>
#include <Interpreters/Cache/Guards.h>
#include <Interpreters/Cache/FileCache_fwd_internal.h>
namespace DB
{
/// IFileCachePriority is used to maintain the priority of cached data.
class IFileCachePriority : private boost::noncopyable
{
public:
using Key = FileCacheKey;
using KeyAndOffset = FileCacheKeyAndOffset;
struct Entry
{
Entry(const Key & key_, size_t offset_, size_t size_, KeyMetadataPtr key_metadata_)
: key(key_), offset(offset_), size(size_), key_metadata(key_metadata_) {}
Entry(const Entry & other)
: key(other.key), offset(other.offset), size(other.size.load()), hits(other.hits), key_metadata(other.key_metadata) {}
const Key key;
const size_t offset;
std::atomic<size_t> size;
size_t hits = 0;
const KeyMetadataPtr key_metadata;
};
/// Provides an iterator to traverse the cache priority. Under normal circumstances,
/// the iterator can only return the records that have been directly swapped out.
/// For example, in the LRU algorithm, it can traverse all records, but in the LRU-K, it
/// can only traverse the records in the low priority queue.
class IIterator
{
public:
virtual ~IIterator() = default;
virtual size_t use(const CacheGuard::Lock &) = 0;
virtual void remove(const CacheGuard::Lock &) = 0;
virtual const Entry & getEntry() const = 0;
virtual Entry & getEntry() = 0;
virtual void invalidate() = 0;
virtual void updateSize(int64_t size) = 0;
};
using Iterator = std::shared_ptr<IIterator>;
using ConstIterator = std::shared_ptr<const IIterator>;
enum class IterationResult
{
BREAK,
CONTINUE,
REMOVE_AND_CONTINUE,
};
using IterateFunc = std::function<IterationResult(LockedKey &, const FileSegmentMetadataPtr &)>;
IFileCachePriority(size_t max_size_, size_t max_elements_) : max_size(max_size_), max_elements(max_elements_) {}
virtual ~IFileCachePriority() = default;
size_t getElementsLimit() const { return max_elements; }
size_t getSizeLimit() const { return max_size; }
virtual size_t getSize(const CacheGuard::Lock &) const = 0;
virtual size_t getElementsCount(const CacheGuard::Lock &) const = 0;
virtual Iterator add(
KeyMetadataPtr key_metadata, size_t offset, size_t size, const CacheGuard::Lock &) = 0;
virtual void pop(const CacheGuard::Lock &) = 0;
virtual void removeAll(const CacheGuard::Lock &) = 0;
/// From lowest to highest priority.
virtual void iterate(IterateFunc && func, const CacheGuard::Lock &) = 0;
virtual void shuffle(const CacheGuard::Lock &) = 0;
private:
const size_t max_size = 0;
const size_t max_elements = 0;
};
}
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