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/* Copyright (c) 2017, 2025, Oracle and/or its affiliates.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License, version 2.0,
as published by the Free Software Foundation.
This program is designed to work with certain software (including
but not limited to OpenSSL) that is licensed under separate terms,
as designated in a particular file or component or in included license
documentation. The authors of MySQL hereby grant you an additional
permission to link the program and your derivative works with the
separately licensed software that they have either included with
the program or referenced in the documentation.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License, version 2.0, for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
#ifndef SQL_LOCK_INCLUDED
#define SQL_LOCK_INCLUDED
#include <sys/types.h>
#include "my_sqlcommand.h" // SQLCOM_LOCK_INSTANCE, SQLCOM_UNLOCK_INSTANCE
#include "sql/sql_cmd.h" // Sql_cmd
class THD;
/**
Sql_cmd_lock_instance represents statement LOCK INSTANCE FOR BACKUP.
*/
class Sql_cmd_lock_instance : public Sql_cmd {
public:
/**
Execute LOCK INSTANCE statement once.
@param thd Thread handler
@returns false on success, true on error
*/
bool execute(THD *thd) override;
enum_sql_command sql_command_code() const override {
return SQLCOM_LOCK_INSTANCE;
}
};
/**
Sql_cmd_unlock_instance represents statement UNLOCK INSTANCE.
*/
class Sql_cmd_unlock_instance : public Sql_cmd {
public:
/**
Execute UNLOCK INSTANCE statement once.
@param thd Thread handler
@returns false on success, true on error
*/
bool execute(THD *thd) override;
enum_sql_command sql_command_code() const override {
return SQLCOM_UNLOCK_INSTANCE;
}
};
/**
MDL_key::BACKUP_LOCK RAII.
*/
class Shared_backup_lock_guard {
public:
/**
There are three possible results while checking if the instance is locked
for backup.
*/
enum class Lock_result { not_locked = 0, locked = 1, oom = 2 };
Shared_backup_lock_guard(THD *thd);
Shared_backup_lock_guard(const Shared_backup_lock_guard &o) = delete;
Shared_backup_lock_guard(Shared_backup_lock_guard &&o) = default;
Shared_backup_lock_guard &operator=(const Shared_backup_lock_guard &o) =
delete;
Shared_backup_lock_guard &operator=(Shared_backup_lock_guard &&o) = default;
~Shared_backup_lock_guard();
operator Lock_result() const;
private:
/**
Try to acquire shared backup lock.
@param[in] thd Current thread context
@param[in] for_trx true if MDL duration is MDL_TRANSACTION
false if MDL duration is MDL_EXPLICIT
@return Operation status.
@retval Shared_backup_lock_guard::Lock_result::locked Locked shared
BACKUP lock.
@retval Shared_backup_lock_guard::Lock_result::not_locked Could not lock
shared BACKUP lock. Conflicting lock exists.
@retval Shared_backup_lock_guard::Lock_result::oom Error. Could
not lock shared BACKUP lock.
*/
Shared_backup_lock_guard::Lock_result try_acquire_shared_backup_lock(
THD *thd, bool for_trx);
Shared_backup_lock_guard::Lock_result m_lock_state;
THD *m_thd;
};
/**
Acquire exclusive Backup Lock.
@param[in] thd Current thread context
@param[in] lock_wait_timeout How many seconds to wait before timeout.
@param[in] for_trx true if MDL duration is MDL_TRANSACTION
false if MDL duration is MDL_EXPLICIT
@return Operation status.
@retval false Success
@retval true Failure
*/
bool acquire_exclusive_backup_lock(THD *thd, unsigned long lock_wait_timeout,
bool for_trx);
/**
Acquire shared Backup Lock.
@param[in] thd Current thread context
@param[in] lock_wait_timeout How many seconds to wait before timeout.
@param[in] for_trx true if MDL duration is MDL_TRANSACTION
false if MDL duration is MDL_EXPLICIT
@return Operation status.
@retval false Success
@retval true Failure
*/
bool acquire_shared_backup_lock(THD *thd, unsigned long lock_wait_timeout,
bool for_trx = true);
/**
Release Backup Lock if it was acquired.
@param[in] thd Current thread context
*/
void release_backup_lock(THD *thd);
#endif /* SQL_LOCK_INCLUDED */
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