test-example-projects/c++_projects/280w-mysql-8.0.18/sql/persisted_variable.h

/* Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.

   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 also distributed 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 included with MySQL.

   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 PERSISTED_VARIABLE_H_INCLUDED
#define PERSISTED_VARIABLE_H_INCLUDED

#include <stddef.h>
#include <map>
#include <string>
#include <vector>

#include "my_alloc.h"
#include "my_inttypes.h"
#include "my_psi_config.h"
#include "mysql/components/services/mysql_mutex_bits.h"
#include "mysql/psi/mysql_mutex.h"
#include "mysql/psi/psi_base.h"
#include "sql_string.h"

class Json_dom;
class THD;
class set_var;
class sys_var;
struct MYSQL_FILE;

/**
  STRUCT st_persist_var

  This structure represents information of a variable which is to
  be persisted in mysql-auto.cnf file.
*/
struct st_persist_var {
  std::string key;
  std::string value;
  ulonglong timestamp;
  std::string user;
  std::string host;
  bool is_null;
  st_persist_var();
  st_persist_var(THD *thd);
  st_persist_var(const std::string key, const std::string value,
                 const ulonglong timestamp, const std::string user,
                 const std::string host, const bool is_null);
};

/**
  CLASS Persisted_variables_cache
    Holds <name,value> pair of all options which needs to be persisted
    to a file.

  OVERVIEW
  --------
  When first SET PERSIST statement is executed we instantiate
  Persisted_variables_cache which loads the config file if present into
  m_persist_variables vector. This is a singleton operation. m_persist_variables
  is an in-memory copy of config file itself. If the SET statement passes then
  this in-memory is updated and flushed to file as an atomic operation.

  Next SET PERSIST statement would only update the in-memory copy and sync
  to config file instead of loading the file again.
*/

#ifdef HAVE_PSI_INTERFACE
void my_init_persist_psi_keys(void);
#endif /* HAVE_PSI_INTERFACE */

class Persisted_variables_cache {
 public:
  int init(int *argc, char ***argv);
  static Persisted_variables_cache *get_instance();
  /**
    Update in-memory copy for every SET PERSIST statement
  */
  void set_variable(THD *thd, set_var *system_var);
  /**
    Flush in-memory copy to persistent file
  */
  bool flush_to_file();
  /**
    Read options from persistent file
  */
  int read_persist_file();
  /**
    Search for persisted config file and if found read persistent options
  */
  bool load_persist_file();
  /**
    Set persisted options
  */
  bool set_persist_options(bool plugin_options = false);
  /**
    Reset persisted options
  */
  bool reset_persisted_variables(THD *thd, const char *name, bool if_exists);
  /**
    Get persisted variables
  */
  std::vector<st_persist_var> *get_persisted_variables();
  /**
    Get persisted static variables
  */
  std::map<std::string, st_persist_var> *get_persist_ro_variables();
  /**
    append read only persisted variables to command line options with a
    separator.
  */
  bool append_read_only_variables(int *argc, char ***argv,
                                  bool plugin_options = false);
  void cleanup();

  /**
    Acquire lock on m_persist_variables/m_persist_ro_variables
  */
  void lock() { mysql_mutex_lock(&m_LOCK_persist_variables); }
  /**
    Release lock on m_persist_variables/m_persist_ro_variables
  */
  void unlock() { mysql_mutex_unlock(&m_LOCK_persist_variables); }
  /**
    Assert caller that owns lock on m_persist_variables/m_persist_ro_variables
  */
  void assert_lock_owner() {
    mysql_mutex_assert_owner(&m_LOCK_persist_variables);
  }

 private:
  /* Helper function to get variable value */
  static String *get_variable_value(THD *thd, sys_var *system_var, String *str,
                                    bool *is_null);
  /* Helper function to get variable name */
  static const char *get_variable_name(sys_var *system_var);
  /* Helper function to construct json formatted string */
  static String *construct_json_string(std::string name, std::string value,
                                       ulonglong timestamp, std::string user,
                                       std::string host, bool is_null,
                                       String *dest);
  /* Helper function to extract variables from json formatted string */
  bool extract_variables_from_json(const Json_dom *dom,
                                   bool is_read_only = false);

 private:
  /* Helper functions for file IO */
  bool open_persist_file(int flag);
  void close_persist_file();

 private:
  /* In memory copy of persistent config file */
  std::vector<st_persist_var> m_persist_variables;
  /* copy of plugin variables whose plugin is not yet installed */
  std::vector<st_persist_var> m_persist_plugin_variables;
  /* In memory copy of read only persistent variables */
  std::map<std::string, st_persist_var> m_persist_ro_variables;

  mysql_mutex_t m_LOCK_persist_variables;
  static Persisted_variables_cache *m_instance;

  /* File handler members */
  MYSQL_FILE *m_fd;
  std::string m_persist_filename;
  mysql_mutex_t m_LOCK_persist_file;
  /* Memory for read only persisted options */
  MEM_ROOT ro_persisted_argv_alloc{PSI_NOT_INSTRUMENTED, 512};
  /* Memory for read only persisted plugin options */
  MEM_ROOT ro_persisted_plugin_argv_alloc{PSI_NOT_INSTRUMENTED, 512};
};

#endif /* PERSISTED_VARIABLE_H_INCLUDED */