71 lines
1.8 KiB
C++
71 lines
1.8 KiB
C++
#ifndef STATEMENT_CACHE_HPP
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#define STATEMENT_CACHE_HPP
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#include "matador/sql/executor.hpp"
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#include "matador/sql/statement.hpp"
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#include <list>
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#include <mutex>
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#include <unordered_map>
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namespace matador::sql {
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class connection_pool;
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struct statement_cache_event {
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enum class Type { Accessed, Added, Evicted };
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Type type;
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std::string sql;
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std::chrono::steady_clock::time_point timestamp;
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};
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class statement_cache_observer_interface {
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public:
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virtual void on_event(const statement_cache_event&) = 0;
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virtual ~statement_cache_observer_interface() = default;
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};
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class statement_cache final {
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private:
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using list_iterator = std::list<size_t>::iterator;
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struct cache_entry {
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statement stmt;
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std::chrono::steady_clock::time_point last_access;
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list_iterator position;
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};
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public:
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explicit statement_cache(connection_pool &pool, size_t max_size = 50);
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statement_cache(const statement_cache &) = delete;
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statement_cache &operator=(const statement_cache &) = delete;
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statement_cache(statement_cache &&) = delete;
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statement_cache &operator=(statement_cache &&) = delete;
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~statement_cache() = default;
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[[nodiscard]] utils::result<statement, utils::error> acquire(const query_context &ctx);
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[[nodiscard]] size_t size() const;
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[[nodiscard]] size_t capacity() const;
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[[nodiscard]] bool empty() const;
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void subscribe(statement_cache_observer_interface &observer);
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private:
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void push(statement_cache_event::Type type, const std::string& sql) const;
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private:
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size_t max_size_{};
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std::list<size_t> usage_list_; // LRU: front = most recent, back = least recent
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std::unordered_map<size_t, cache_entry> cache_map_;
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std::mutex mutex_;
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connection_pool &pool_;
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const sql::dialect &dialect_;
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std::vector<statement_cache_observer_interface*> observers_;
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};
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}
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#endif //STATEMENT_CACHE_HPP
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