locked_sidno_set.h

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#ifndef CHANGESTREAMS_INDEX_LOCKED_SIDNO_SET_H_INCLUDED
#define CHANGESTREAMS_INDEX_LOCKED_SIDNO_SET_H_INCLUDED
 
#include <functional>
#include <set>
#include "sql/changestreams/index/sidno.h"
#include "sql/rpl_gtid.h"
 
class Gtid_state;
 
namespace cs::index {
 
/// @brief Set that keeps track of TSID locks taken in the current scope.
/// Provides dead-lock free mechanism for added sidnos, as sidnos are ordered
/// in the set insuring a deterministic lock order
/// Locks are added to the set by execution of the add_lock_for_sidno.
/// Later, the user may call lock(), which will lock all recorded sidno locks.
/// Locks will be released in destructor.
/// @details Used to optimize TSID locking/unlocking scheme (e.g. in
/// assign_automatic_gtids_to_flush_group) to avoid constant locking/unlocking
/// of TSID locks during the commit flush stage
class Locked_sidno_set {
 public:
  Locked_sidno_set(Gtid_state &gtid_state);
  Locked_sidno_set(Locked_sidno_set &src) = delete;
 
  /// @brief Adds a given sidno to the internal set, does not acquire ownership
  /// @param sidno TSID being considered
  /// @details may be called several times for one sidno
  void add_lock_for_sidno(rpl_sidno sidno);
 
  /// @brief Locks recorded sidno locks, in order. In case set is already
  /// locked, function does not take any action
  void lock();
 
  /// @brief Destructor, releases all locks kept in the set
  ~Locked_sidno_set();
 
 protected:
  using Set_type = std::set<rpl_sidno>;  ///< Type of the set used
  Set_type m_sidno_set;  ///< SIDs for which lock will be acquired
  std::reference_wrapper<Gtid_state>
      m_gtid_state;  ///< Reference to the current Gtid_state object (avoids
                     ///< using the global gtid_state variable in the class)
  bool m_locked = false;  ///< Is set currently locked?
};
 
}  // namespace cs::index
 
#endif  // CHANGESTREAMS_INDEX_LOCKED_SIDNO_SET_H_INCLUDED