mariadb/sql/sys_vars.cc

/* Copyright (C) 2002-2006 MySQL AB, 2009 Sun Microsystems, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   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 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/*
  How to add new variables:

  1. copy one of the existing variables, and edit the declaration.
  2. if you need special behavior on assignment or additional checks
     use ON_CHECK and ON_UPDATE callbacks.
  3. *Don't* add new Sys_var classes or uncle Occam will come
     with his razor to haunt you at nights

  Note - all storage engine variables (for example myisam_whatever)
  should go into the corresponding storage engine sources
  (for example in storage/myisam/ha_myisam.cc) !
*/

#include "sys_vars.h"

#include "events.h"
#include <thr_alarm.h>
#include "slave.h"
#include "rpl_mi.h"
#include "transaction.h"

/*
  The rule for this file: everything should be 'static'. When a sys_var
  variable or a function from this file is - in very rare cases - needed
  elsewhere it should be explicitly declared 'export' here to show that it's
  not a mistakenly forgotten 'static' keyword.
*/
#define export /* not static */

static Sys_var_ulong Sys_auto_increment_increment(
       "auto_increment_increment",
       "Auto-increment columns are incremented by this",
       SESSION_VAR(auto_increment_increment),
       CMD_LINE(OPT_ARG),
       VALID_RANGE(1, 65535), DEFAULT(1), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, IN_BINLOG);

static Sys_var_ulong Sys_auto_increment_offset(
       "auto_increment_offset",
       "Offset added to Auto-increment columns. Used when "
       "auto-increment-increment != 1",
       SESSION_VAR(auto_increment_offset),
       CMD_LINE(OPT_ARG),
       VALID_RANGE(1, 65535), DEFAULT(1), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, IN_BINLOG);

static Sys_var_mybool Sys_automatic_sp_privileges(
       "automatic_sp_privileges",
       "Creating and dropping stored procedures alters ACLs",
       GLOBAL_VAR(sp_automatic_privileges),
       CMD_LINE(OPT_ARG), DEFAULT(TRUE));

static Sys_var_ulong Sys_back_log(
       "back_log", "The number of outstanding connection requests "
       "MySQL can have. This comes into play when the main MySQL thread "
       "gets very many connection requests in a very short time",
       READ_ONLY GLOBAL_VAR(back_log), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, 65535), DEFAULT(50), BLOCK_SIZE(1));

static Sys_var_charptr Sys_basedir(
       "basedir", "Path to installation directory. All paths are "
       "usually resolved relative to this",
       READ_ONLY GLOBAL_VAR(mysql_home_ptr), CMD_LINE(REQUIRED_ARG, 'b'),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_ulong Sys_binlog_cache_size(
       "binlog_cache_size", "The size of the cache to "
       "hold the SQL statements for the binary log during a "
       "transaction. If you often use big, multi-statement "
       "transactions you can increase this to get more performance",
       GLOBAL_VAR(binlog_cache_size),
       CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(IO_SIZE, ULONG_MAX), DEFAULT(32768), BLOCK_SIZE(IO_SIZE));

static bool check_has_super(sys_var *self, THD *thd, set_var *var)
{
  DBUG_ASSERT(self->scope() != sys_var::GLOBAL);// don't abuse check_has_super()
#ifndef NO_EMBEDDED_ACCESS_CHECKS
  if (!(thd->security_ctx->master_access & SUPER_ACL))
  {
    my_error(ER_SPECIFIC_ACCESS_DENIED_ERROR, MYF(0), "SUPER");
    return true;
  }
#endif
  return false;
}
static bool binlog_format_check(sys_var *self, THD *thd, set_var *var)
{
  if (check_has_super(self, thd, var))
    return true;
  if (var->type == OPT_GLOBAL ||
      (thd->variables.binlog_format == var->save_result.ulonglong_value))
    return false;

  /*
    If RBR and open temporary tables, their CREATE TABLE may not be in the
    binlog, so we can't toggle to SBR in this connection.
  */
  if ((thd->variables.binlog_format == BINLOG_FORMAT_ROW) &&
      thd->temporary_tables)
  {
    my_error(ER_TEMP_TABLE_PREVENTS_SWITCH_OUT_OF_RBR, MYF(0));
    return true;
  }
  /*
    if in a stored function/trigger, it's too late to change mode
  */
  if (thd->in_sub_stmt)
  {
    my_error(ER_STORED_FUNCTION_PREVENTS_SWITCH_BINLOG_FORMAT, MYF(0));
    return true;
  }
  return false;
}

static bool fix_binlog_format_after_update(sys_var *self, THD *thd,
                                           enum_var_type type)
{
  if (type == OPT_SESSION)
    thd->reset_current_stmt_binlog_row_based();
  return false;
}

static Sys_var_enum Sys_binlog_format(
       "binlog_format", "What form of binary logging the master will "
       "use: either ROW for row-based binary logging, STATEMENT "
       "for statement-based binary logging, or MIXED. MIXED is statement-"
       "based binary logging except for those statements where only row-"
       "based is correct: those which involve user-defined functions (i.e. "
       "UDFs) or the UUID() function; for those, row-based binary logging is "
       "automatically used. If NDBCLUSTER is enabled and binlog-format is "
       "MIXED, the format switches to row-based and back implicitly per each "
       "query accessing an NDBCLUSTER table",
       SESSION_VAR(binlog_format), CMD_LINE(REQUIRED_ARG, OPT_BINLOG_FORMAT),
       binlog_format_names, DEFAULT(BINLOG_FORMAT_STMT),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(binlog_format_check),
       ON_UPDATE(fix_binlog_format_after_update));

static Sys_var_ulong Sys_bulk_insert_buff_size(
       "bulk_insert_buffer_size", "Size of tree cache used in bulk "
       "insert optimisation. Note that this is a limit per thread!",
       SESSION_VAR(bulk_insert_buff_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, ULONG_MAX), DEFAULT(8192*1024), BLOCK_SIZE(1));

static Sys_var_charptr Sys_character_sets_dir(
       "character_sets_dir", "Directory where character sets are",
       READ_ONLY GLOBAL_VAR(charsets_dir), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0));

static bool check_not_null(sys_var *self, THD *thd, set_var *var)
{
  return var->value && var->value->is_null();
}
static bool check_charset(sys_var *self, THD *thd, set_var *var)
{
  if (!var->value)
    return false;

  char buff[STRING_BUFFER_USUAL_SIZE];
  if (var->value->result_type() == STRING_RESULT)
  {
    String str(buff, sizeof(buff), system_charset_info), *res;
    if (!(res=var->value->val_str(&str)))
      var->save_result.ptr= NULL;
    else if (!(var->save_result.ptr= get_charset_by_csname(res->c_ptr(),
                                                           MY_CS_PRIMARY,
                                                           MYF(0))) &&
             !(var->save_result.ptr= get_old_charset_by_name(res->c_ptr())))
    {
      ErrConvString err(res);
      my_error(ER_UNKNOWN_CHARACTER_SET, MYF(0), err.ptr());
      return true;
    }
  }
  else // INT_RESULT
  {
    int csno= (int)var->value->val_int();
    if (!(var->save_result.ptr= get_charset(csno, MYF(0))))
    {
      my_error(ER_UNKNOWN_CHARACTER_SET, MYF(0), llstr(csno, buff));
      return true;
    }
  }
  return false;
}
static bool check_charset_not_null(sys_var *self, THD *thd, set_var *var)
{
  return check_charset(self, thd, var) || check_not_null(self, thd, var);
}
static Sys_var_struct Sys_character_set_system(
       "character_set_system", "The character set used by the server "
       "for storing identifiers",
       READ_ONLY GLOBAL_VAR(system_charset_info), NO_CMD_LINE,
       offsetof(CHARSET_INFO, csname), DEFAULT(0));

static Sys_var_struct Sys_character_set_server(
       "character_set_server", "The default character set",
       SESSION_VAR(collation_server), NO_CMD_LINE,
       offsetof(CHARSET_INFO, csname), DEFAULT(&default_charset_info),
       NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(check_charset_not_null));

static bool check_charset_db(sys_var *self, THD *thd, set_var *var)
{
  if (check_charset_not_null(self, thd, var))
    return true;
  if (!var->value) // = DEFAULT
    var->save_result.ptr= thd->db_charset;
  return false;
}
static Sys_var_struct Sys_character_set_database(
       "character_set_database",
       " The character set used by the default database",
       SESSION_VAR(collation_database), NO_CMD_LINE,
       offsetof(CHARSET_INFO, csname), DEFAULT(&default_charset_info),
       NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(check_charset_db));

static bool check_cs_client(sys_var *self, THD *thd, set_var *var)
{
  if (check_charset_not_null(self, thd, var))
    return true;

  // Currently, UCS-2 cannot be used as a client character set
  if (((CHARSET_INFO *)(var->save_result.ptr))->mbminlen > 1)
    return true;

  return false;
}
static bool fix_thd_charset(sys_var *self, THD *thd, enum_var_type type)
{
  if (type == OPT_SESSION)
    thd->update_charset();
  return false;
}
static Sys_var_struct Sys_character_set_client(
       "character_set_client", "The character set for statements "
       "that arrive from the client",
       SESSION_VAR(character_set_client), NO_CMD_LINE,
       offsetof(CHARSET_INFO, csname), DEFAULT(&default_charset_info),
       NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(check_cs_client),
       ON_UPDATE(fix_thd_charset));

static Sys_var_struct Sys_character_set_connection(
       "character_set_connection", "The character set used for "
       "literals that do not have a character set introducer and for "
       "number-to-string conversion",
       SESSION_VAR(collation_connection), NO_CMD_LINE,
       offsetof(CHARSET_INFO, csname), DEFAULT(&default_charset_info),
       NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(check_charset_not_null),
       ON_UPDATE(fix_thd_charset));

static Sys_var_struct Sys_character_set_results(
       "character_set_results", "The character set used for returning "
       "query results to the client",
       SESSION_VAR(character_set_results), NO_CMD_LINE,
       offsetof(CHARSET_INFO, csname), DEFAULT(&default_charset_info),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(check_charset));

static Sys_var_struct Sys_character_set_filesystem(
       "character_set_filesystem", "The filesystem character set",
       SESSION_VAR(character_set_filesystem), NO_CMD_LINE,
       offsetof(CHARSET_INFO, csname), DEFAULT(&character_set_filesystem),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(check_charset_not_null),
       ON_UPDATE(fix_thd_charset));

static const char *completion_type_names[]= {"NO_CHAIN", "CHAIN", "RELEASE", 0};
static Sys_var_enum Sys_completion_type(
       "completion_type", "The transaction completion type, one of "
       "NO_CHAIN, CHAIN, RELEASE",
       SESSION_VAR(completion_type), CMD_LINE(REQUIRED_ARG),
       completion_type_names, DEFAULT(0));

static bool check_collation_not_null(sys_var *self, THD *thd, set_var *var)
{
  if (!var->value)
    return false;

  char buff[STRING_BUFFER_USUAL_SIZE];
  if (var->value->result_type() == STRING_RESULT)
  {
    String str(buff, sizeof(buff), system_charset_info), *res;
    if (!(res= var->value->val_str(&str)))
      var->save_result.ptr= NULL;
    else if (!(var->save_result.ptr= get_charset_by_name(res->c_ptr(), MYF(0))))
    {
      ErrConvString err(res);
      my_error(ER_UNKNOWN_COLLATION, MYF(0), err.ptr());
      return true;
    }
  }
  else // INT_RESULT
  {
    int csno= (int)var->value->val_int();
    if (!(var->save_result.ptr= get_charset(csno, MYF(0))))
    {
      my_error(ER_UNKNOWN_COLLATION, MYF(0), llstr(csno, buff));
      return true;
    }
  }
  return check_not_null(self, thd, var);
}
static Sys_var_struct Sys_collation_connection(
       "collation_connection", "The collation of the connection "
       "character set",
       SESSION_VAR(collation_connection), NO_CMD_LINE,
       offsetof(CHARSET_INFO, name), DEFAULT(&default_charset_info),
       NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(check_collation_not_null),
       ON_UPDATE(fix_thd_charset));

static bool check_collation_db(sys_var *self, THD *thd, set_var *var)
{
  if (check_collation_not_null(self, thd, var))
    return true;
  if (!var->value) // = DEFAULT
    var->save_result.ptr= thd->db_charset;
  return false;
}
static Sys_var_struct Sys_collation_database(
       "collation_database", "The collation of the database "
       "character set",
       SESSION_VAR(collation_database), NO_CMD_LINE,
       offsetof(CHARSET_INFO, name), DEFAULT(&default_charset_info),
       NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(check_collation_db));

static Sys_var_struct Sys_collation_server(
       "collation_server", "The server default collation",
       SESSION_VAR(collation_server), NO_CMD_LINE,
       offsetof(CHARSET_INFO, name), DEFAULT(&default_charset_info),
       NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(check_collation_not_null));

static const char *concurrent_insert_names[]= {"NEVER", "AUTO", "ALWAYS", 0};
static Sys_var_enum Sys_concurrent_insert(
       "concurrent_insert", "Use concurrent insert with MyISAM. Possible "
       "values are NEVER, AUTO, ALWAYS",
       GLOBAL_VAR(myisam_concurrent_insert), CMD_LINE(OPT_ARG),
       concurrent_insert_names, DEFAULT(1));

static Sys_var_ulong Sys_connect_timeout(
       "connect_timeout",
       "The number of seconds the mysqld server is waiting for a connect "
       "packet before responding with 'Bad handshake'",
       GLOBAL_VAR(connect_timeout), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(2, LONG_TIMEOUT), DEFAULT(CONNECT_TIMEOUT), BLOCK_SIZE(1));

static Sys_var_charptr Sys_datadir(
       "datadir", "Path to the database root directory",
       READ_ONLY GLOBAL_VAR(mysql_real_data_home_ptr),
       CMD_LINE(REQUIRED_ARG, 'h'), IN_FS_CHARSET, DEFAULT(0));

#ifndef DBUG_OFF
static Sys_var_dbug Sys_dbug(
       "debug", "Debug log", sys_var::SESSION,
       CMD_LINE(OPT_ARG, '#'), DEFAULT(""), NO_MUTEX_GUARD, NOT_IN_BINLOG,
       ON_CHECK(check_has_super));
#endif

/**
  @todo
    When updating myisam_delay_key_write, we should do a 'flush tables'
    of all MyISAM tables to ensure that they are reopen with the
    new attribute.
*/
export bool fix_delay_key_write(sys_var *self, THD *thd, enum_var_type type)
{
  switch (delay_key_write_options) {
  case DELAY_KEY_WRITE_NONE:
    myisam_delay_key_write=0;
    break;
  case DELAY_KEY_WRITE_ON:
    myisam_delay_key_write=1;
    break;
  case DELAY_KEY_WRITE_ALL:
    myisam_delay_key_write=1;
    ha_open_options|= HA_OPEN_DELAY_KEY_WRITE;
    break;
  }
  return false;
}
static const char *delay_key_write_names[]= { "OFF", "ON", "ALL", NullS };
static Sys_var_enum Sys_delay_key_write(
       "delay_key_write", "Type of DELAY_KEY_WRITE",
       GLOBAL_VAR(delay_key_write_options), CMD_LINE(OPT_ARG),
       delay_key_write_names, DEFAULT(DELAY_KEY_WRITE_ON),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_delay_key_write));

static Sys_var_ulong Sys_delayed_insert_limit(
       "delayed_insert_limit",
       "After inserting delayed_insert_limit rows, the INSERT DELAYED "
       "handler will check if there are any SELECT statements pending. "
       "If so, it allows these to execute before continuing",
       GLOBAL_VAR(delayed_insert_limit), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, ULONG_MAX), DEFAULT(DELAYED_LIMIT), BLOCK_SIZE(1));

static Sys_var_ulong Sys_delayed_insert_timeout(
       "delayed_insert_timeout",
       "How long a INSERT DELAYED thread should wait for INSERT statements "
       "before terminating",
       GLOBAL_VAR(delayed_insert_timeout), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, LONG_TIMEOUT), DEFAULT(DELAYED_WAIT_TIMEOUT),
       BLOCK_SIZE(1));

static Sys_var_ulong Sys_delayed_queue_size(
       "delayed_queue_size",
       "What size queue (in rows) should be allocated for handling INSERT "
       "DELAYED. If the queue becomes full, any client that does INSERT "
       "DELAYED will wait until there is room in the queue again",
       GLOBAL_VAR(delayed_queue_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, ULONG_MAX), DEFAULT(DELAYED_QUEUE_SIZE), BLOCK_SIZE(1));

#ifdef HAVE_EVENT_SCHEDULER
static const char *event_scheduler_names[]= { "OFF", "ON", "DISABLED", NullS };
static bool event_scheduler_check(sys_var *self, THD *thd, set_var *var)
{
  /* DISABLED is only accepted on the command line */
  if (var->save_result.ulonglong_value == Events::EVENTS_DISABLED)
    return true;
  /*
    If the scheduler was disabled because there are no/bad
    system tables, produce a more meaningful error message
    than ER_OPTION_PREVENTS_STATEMENT
  */
  if (Events::check_if_system_tables_error())
    return true;
  if (Events::opt_event_scheduler == Events::EVENTS_DISABLED)
  {
    my_error(ER_OPTION_PREVENTS_STATEMENT, MYF(0),
             "--event-scheduler=DISABLED or --skip-grant-tables");
    return true;
  }
  return false;
}
static bool event_scheduler_update(sys_var *self, THD *thd, enum_var_type type)
{
  pthread_mutex_unlock(&LOCK_global_system_variables);
  /*
    Events::start() is heavyweight. In particular it creates a new THD,
    which takes LOCK_global_system_variables internally.
    Thus we have to release it here.
    We need to re-take it before returning, though.
    And we need to take it *without* holding Events::LOCK_event_metadata.
  */
  bool ret= Events::opt_event_scheduler == Events::EVENTS_ON
            ? Events::start()
            : Events::stop();
  pthread_mutex_unlock(&Events::LOCK_event_metadata);
  pthread_mutex_lock(&LOCK_global_system_variables);
  pthread_mutex_lock(&Events::LOCK_event_metadata);
  if (ret)
    my_error(ER_EVENT_SET_VAR_ERROR, MYF(0));
  return ret;
}
static PolyLock_mutex PLock_event_metadata(&Events::LOCK_event_metadata);
static Sys_var_enum Sys_event_scheduler(
       "event_scheduler", "Enable the event scheduler. Possible values are "
       "ON, OFF, and DISABLED (keep the event scheduler completely "
       "deactivated, it cannot be activated run-time)",
       GLOBAL_VAR(Events::opt_event_scheduler), CMD_LINE(OPT_ARG),
       event_scheduler_names, DEFAULT(Events::EVENTS_OFF),
       &PLock_event_metadata, NOT_IN_BINLOG,
       ON_CHECK(event_scheduler_check), ON_UPDATE(event_scheduler_update));
#endif

static Sys_var_ulong Sys_expire_logs_days(
       "expire_logs_days",
       "If non-zero, binary logs will be purged after expire_logs_days "
       "days; possible purges happen at startup and at binary log rotation",
       GLOBAL_VAR(expire_logs_days),
       CMD_LINE(REQUIRED_ARG), VALID_RANGE(0, 99), DEFAULT(0), BLOCK_SIZE(1));

static Sys_var_mybool Sys_flush(
       "flush", "Flush MyISAM tables to disk between SQL commands",
       GLOBAL_VAR(myisam_flush),
       CMD_LINE(OPT_ARG), DEFAULT(FALSE));

static Sys_var_ulong Sys_flush_time(
       "flush_time",
       "A dedicated thread is created to flush all tables at the "
       "given interval",
       GLOBAL_VAR(flush_time),
       CMD_LINE(REQUIRED_ARG), VALID_RANGE(0, LONG_TIMEOUT),
       DEFAULT(FLUSH_TIME), BLOCK_SIZE(1));

static bool check_ftb_syntax(sys_var *self, THD *thd, set_var *var)
{
  return ft_boolean_check_syntax_string((uchar*)
                      (var->save_result.string_value.str));
}
static bool query_cache_flush(sys_var *self, THD *thd, enum_var_type type)
{
#ifdef HAVE_QUERY_CACHE
  query_cache.flush();
#endif /* HAVE_QUERY_CACHE */
  return false;
}
/// @todo make SESSION_VAR (usability enhancement and a fix for a race condition)
static Sys_var_charptr Sys_ft_boolean_syntax(
       "ft_boolean_syntax", "List of operators for "
       "MATCH ... AGAINST ( ... IN BOOLEAN MODE)",
       GLOBAL_VAR(ft_boolean_syntax),
       CMD_LINE(REQUIRED_ARG), IN_SYSTEM_CHARSET,
       DEFAULT(DEFAULT_FTB_SYNTAX), NO_MUTEX_GUARD,
       NOT_IN_BINLOG, ON_CHECK(check_ftb_syntax), ON_UPDATE(query_cache_flush));

static Sys_var_ulong Sys_ft_max_word_len(
       "ft_max_word_len",
       "The maximum length of the word to be included in a FULLTEXT index. "
       "Note: FULLTEXT indexes must be rebuilt after changing this variable",
       READ_ONLY GLOBAL_VAR(ft_max_word_len), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(10, HA_FT_MAXCHARLEN), DEFAULT(HA_FT_MAXCHARLEN),
       BLOCK_SIZE(1));

static Sys_var_ulong Sys_ft_min_word_len(
       "ft_min_word_len",
       "The minimum length of the word to be included in a FULLTEXT index. "
       "Note: FULLTEXT indexes must be rebuilt after changing this variable",
       READ_ONLY GLOBAL_VAR(ft_min_word_len), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, HA_FT_MAXCHARLEN), DEFAULT(4), BLOCK_SIZE(1));

/// @todo make it an updatable SESSION_VAR
static Sys_var_ulong Sys_ft_query_expansion_limit(
       "ft_query_expansion_limit",
       "Number of best matches to use for query expansion",
       READ_ONLY GLOBAL_VAR(ft_query_expansion_limit),
       CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, 1000), DEFAULT(20), BLOCK_SIZE(1));

static Sys_var_charptr Sys_ft_stopword_file(
       "ft_stopword_file",
       "Use stopwords from this file instead of built-in list",
       READ_ONLY GLOBAL_VAR(ft_stopword_file), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_mybool Sys_ignore_builtin_innodb(
       "ignore_builtin_innodb",
       "Disable initialization of builtin InnoDB plugin",
       READ_ONLY GLOBAL_VAR(opt_ignore_builtin_innodb),
       CMD_LINE(OPT_ARG), DEFAULT(FALSE));

static bool check_init_string(sys_var *self, THD *thd, set_var *var)
{
  if (var->save_result.string_value.str == 0)
  {
    var->save_result.string_value.str= const_cast<char*>("");
    var->save_result.string_value.length= 0;
  }
  return false;
}
static PolyLock_rwlock PLock_sys_init_connect(&LOCK_sys_init_connect);
static Sys_var_lexstring Sys_init_connect(
       "init_connect", "Command(s) that are executed for each "
       "new connection", GLOBAL_VAR(opt_init_connect),
       CMD_LINE(REQUIRED_ARG), IN_SYSTEM_CHARSET,
       DEFAULT(""), &PLock_sys_init_connect, NOT_IN_BINLOG,
       ON_CHECK(check_init_string));

static Sys_var_charptr Sys_init_file(
       "init_file", "Read SQL commands from this file at startup",
       READ_ONLY GLOBAL_VAR(opt_init_file),
       IF_DISABLE_GRANT_OPTIONS(NO_CMD_LINE, CMD_LINE(REQUIRED_ARG)),
       IN_FS_CHARSET, DEFAULT(0));

static PolyLock_rwlock PLock_sys_init_slave(&LOCK_sys_init_slave);
static Sys_var_lexstring Sys_init_slave(
       "init_slave", "Command(s) that are executed by a slave server "
       "each time the SQL thread starts", GLOBAL_VAR(opt_init_slave),
       CMD_LINE(REQUIRED_ARG), IN_SYSTEM_CHARSET,
       DEFAULT(""), &PLock_sys_init_slave,
       NOT_IN_BINLOG, ON_CHECK(check_init_string));

static Sys_var_ulong Sys_interactive_timeout(
       "interactive_timeout",
       "The number of seconds the server waits for activity on an interactive "
       "connection before closing it",
       SESSION_VAR(net_interactive_timeout),
       CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, LONG_TIMEOUT), DEFAULT(NET_WAIT_TIMEOUT), BLOCK_SIZE(1));

static Sys_var_ulong Sys_join_buffer_size(
       "join_buffer_size",
       "The size of the buffer that is used for full joins",
       SESSION_VAR(join_buff_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(128, ULONG_MAX), DEFAULT(128*1024), BLOCK_SIZE(128));

static Sys_var_keycache Sys_key_buffer_size(
       "key_buffer_size", "The size of the buffer used for "
       "index blocks for MyISAM tables. Increase this to get better index "
       "handling (for all reads and multiple writes) to as much as you can "
       "afford",
       KEYCACHE_VAR(param_buff_size),
       CMD_LINE(REQUIRED_ARG, OPT_KEY_BUFFER_SIZE),
       VALID_RANGE(0, SIZE_T_MAX), DEFAULT(KEY_CACHE_SIZE),
       BLOCK_SIZE(IO_SIZE), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(update_buffer_size));

static Sys_var_keycache Sys_key_cache_block_size(
       "key_cache_block_size", "The default size of key cache blocks",
       KEYCACHE_VAR(param_block_size),
       CMD_LINE(REQUIRED_ARG, OPT_KEY_CACHE_BLOCK_SIZE),
       VALID_RANGE(512, 1024*16), DEFAULT(KEY_CACHE_BLOCK_SIZE),
       BLOCK_SIZE(512), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(update_keycache_param));

static Sys_var_keycache Sys_key_cache_division_limit(
       "key_cache_division_limit",
       "The minimum percentage of warm blocks in key cache",
       KEYCACHE_VAR(param_division_limit),
       CMD_LINE(REQUIRED_ARG, OPT_KEY_CACHE_DIVISION_LIMIT),
       VALID_RANGE(1, 100), DEFAULT(100),
       BLOCK_SIZE(1), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(update_keycache_param));

static Sys_var_keycache Sys_key_cache_age_threshold(
       "key_cache_age_threshold", "This characterizes the number of "
       "hits a hot block has to be untouched until it is considered aged "
       "enough to be downgraded to a warm block. This specifies the "
       "percentage ratio of that number of hits to the total number of "
       "blocks in key cache",
       KEYCACHE_VAR(param_age_threshold),
       CMD_LINE(REQUIRED_ARG, OPT_KEY_CACHE_AGE_THRESHOLD),
       VALID_RANGE(100, ULONG_MAX), DEFAULT(300),
       BLOCK_SIZE(100), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(update_keycache_param));

static Sys_var_mybool Sys_large_files_support(
       "large_files_support",
       "Whether mysqld was compiled with options for large file support",
       READ_ONLY GLOBAL_VAR(opt_large_files),
       NO_CMD_LINE, DEFAULT(sizeof(my_off_t) > 4));

static Sys_var_uint Sys_large_page_size(
       "large_page_size",
       "If large page support is enabled, this shows the size of memory pages",
       READ_ONLY GLOBAL_VAR(opt_large_page_size), NO_CMD_LINE,
       VALID_RANGE(0, UINT_MAX), DEFAULT(0), BLOCK_SIZE(1));

static Sys_var_mybool Sys_large_pages(
       "large_pages", "Enable support for large pages",
       READ_ONLY GLOBAL_VAR(opt_large_files),
       IF_WIN(NO_CMD_LINE, CMD_LINE(OPT_ARG)), DEFAULT(FALSE));

static Sys_var_charptr Sys_language(
       "lc_messages_dir", "Directory where error messages are",
       READ_ONLY GLOBAL_VAR(lc_messages_dir_ptr), CMD_LINE(REQUIRED_ARG, 'L'),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_mybool Sys_local_infile(
       "local_infile", "Enable LOAD DATA LOCAL INFILE",
       GLOBAL_VAR(opt_local_infile), CMD_LINE(OPT_ARG), DEFAULT(TRUE));

#ifdef HAVE_MLOCKALL
static Sys_var_mybool Sys_locked_in_memory(
       "locked_in_memory",
       "Whether mysqld was locked in memory with --memlock",
       READ_ONLY GLOBAL_VAR(locked_in_memory), NO_CMD_LINE, DEFAULT(FALSE));
#endif

/* this says NO_CMD_LINE, as command-line option takes a string, not a bool */
static Sys_var_mybool Sys_log_bin(
       "log_bin", "Whether the binary log is enabled",
       READ_ONLY GLOBAL_VAR(opt_bin_log), NO_CMD_LINE, DEFAULT(FALSE));

static Sys_var_mybool Sys_trust_function_creators(
       "log_bin_trust_function_creators",
       "If set to FALSE (the default), then when --log-bin is used, creation "
       "of a stored function (or trigger) is allowed only to users having the "
       "SUPER privilege and only if this stored function (trigger) may not "
       "break binary logging. Note that if ALL connections to this server "
       "ALWAYS use row-based binary logging, the security issues do not "
       "exist and the binary logging cannot break, so you can safely set "
       "this to TRUE",
       GLOBAL_VAR(trust_function_creators),
       CMD_LINE(OPT_ARG), DEFAULT(FALSE));

static Sys_var_charptr Sys_log_error(
       "log_error", "Error log file",
       READ_ONLY GLOBAL_VAR(log_error_file_ptr), CMD_LINE(OPT_ARG),
       IN_FS_CHARSET, DEFAULT(disabled_my_option));

static Sys_var_mybool Sys_log_queries_not_using_indexes(
       "log_queries_not_using_indexes",
       "Log queries that are executed without benefit of any index to the "
       "slow log if it is open",
       GLOBAL_VAR(opt_log_queries_not_using_indexes),
       CMD_LINE(OPT_ARG), DEFAULT(FALSE));

static Sys_var_ulong Sys_log_warnings(
       "log_warnings",
       "Log some not critical warnings to the log file",
       SESSION_VAR(log_warnings),
       CMD_LINE(OPT_ARG, 'W'),
       VALID_RANGE(0, ULONG_MAX), DEFAULT(1), BLOCK_SIZE(1));

static bool update_cached_long_query_time(sys_var *self, THD *thd,
                                          enum_var_type type)
{
  if (type == OPT_SESSION)
    thd->variables.long_query_time=
      thd->variables.long_query_time_double * 1e6;
  else
    global_system_variables.long_query_time=
      global_system_variables.long_query_time_double * 1e6;
  return false;
}

static Sys_var_double Sys_long_query_time(
       "long_query_time",
       "Log all queries that have taken more than long_query_time seconds "
       "to execute to file. The argument will be treated as a decimal value "
       "with microsecond precision",
       SESSION_VAR(long_query_time_double),
       CMD_LINE(REQUIRED_ARG), VALID_RANGE(0, LONG_TIMEOUT), DEFAULT(10),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(update_cached_long_query_time));

static bool fix_low_prio_updates(sys_var *self, THD *thd, enum_var_type type)
{
  if (type == OPT_SESSION)
    thd->update_lock_default= (thd->variables.low_priority_updates ?
                               TL_WRITE_LOW_PRIORITY : TL_WRITE);
  else
    thr_upgraded_concurrent_insert_lock=
      (global_system_variables.low_priority_updates ?
       TL_WRITE_LOW_PRIORITY : TL_WRITE);
  return false;
}
static Sys_var_mybool Sys_low_priority_updates(
       "low_priority_updates",
       "INSERT/DELETE/UPDATE has lower priority than selects",
       SESSION_VAR(low_priority_updates),
       CMD_LINE(OPT_ARG),
       DEFAULT(FALSE), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_low_prio_updates));

#ifndef TO_BE_DELETED   /* Alias for the low_priority_updates */
static Sys_var_mybool Sys_sql_low_priority_updates(
       "sql_low_priority_updates",
       "INSERT/DELETE/UPDATE has lower priority than selects",
       SESSION_VAR(low_priority_updates), NO_CMD_LINE,
       DEFAULT(FALSE), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_low_prio_updates));
#endif

static Sys_var_mybool Sys_lower_case_file_system(
       "lower_case_file_system",
       "Case sensitivity of file names on the file system where the "
       "data directory is located",
       READ_ONLY GLOBAL_VAR(lower_case_file_system), NO_CMD_LINE,
       DEFAULT(FALSE));

static Sys_var_uint Sys_lower_case_table_names(
       "lower_case_table_names",
       "If set to 1 table names are stored in lowercase on disk and table "
       "names will be case-insensitive.  Should be set to 2 if you are using "
       "a case insensitive file system",
       READ_ONLY GLOBAL_VAR(lower_case_table_names),
       CMD_LINE(OPT_ARG, OPT_LOWER_CASE_TABLE_NAMES),
       VALID_RANGE(0, 2),
#ifdef FN_NO_CASE_SENSE
    DEFAULT(1),
#else
    DEFAULT(0),
#endif
       BLOCK_SIZE(1));

static bool session_readonly(sys_var *self, THD *thd, set_var *var)
{
  if (var->type == OPT_GLOBAL)
    return false;
  my_error(ER_VARIABLE_IS_READONLY, MYF(0), "SESSION",
           self->name.str, "GLOBAL");
  return true;
}
static Sys_var_ulong Sys_max_allowed_packet(
       "max_allowed_packet",
       "Max packet length to send to or receive from the server",
       SESSION_VAR(max_allowed_packet), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1024, 1024*1024*1024), DEFAULT(1024*1024),
       BLOCK_SIZE(1024), NO_MUTEX_GUARD, NOT_IN_BINLOG,
       ON_CHECK(session_readonly));

static Sys_var_ulonglong Sys_max_binlog_cache_size(
       "max_binlog_cache_size",
       "Can be used to restrict the total size used to cache a "
       "multi-transaction query",
       GLOBAL_VAR(max_binlog_cache_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(IO_SIZE, ULONGLONG_MAX),
       DEFAULT((ULONGLONG_MAX/IO_SIZE)*IO_SIZE),
       BLOCK_SIZE(IO_SIZE));

static bool fix_max_binlog_size(sys_var *self, THD *thd, enum_var_type type)
{
  mysql_bin_log.set_max_size(max_binlog_size);
#ifdef HAVE_REPLICATION
  if (!max_relay_log_size)
    active_mi->rli.relay_log.set_max_size(max_binlog_size);
#endif
  return false;
}
static Sys_var_ulong Sys_max_binlog_size(
       "max_binlog_size",
       "Binary log will be rotated automatically when the size exceeds this "
       "value. Will also apply to relay logs if max_relay_log_size is 0",
       GLOBAL_VAR(max_binlog_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(IO_SIZE, 1024*1024L*1024L), DEFAULT(1024*1024L*1024L),
       BLOCK_SIZE(IO_SIZE), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_max_binlog_size));

static bool fix_max_connections(sys_var *self, THD *thd, enum_var_type type)
{
#ifndef EMBEDDED_LIBRARY
  resize_thr_alarm(max_connections +
                   global_system_variables.max_insert_delayed_threads + 10);
#endif
  return false;
}

// Default max_connections of 151 is larger than Apache's default max
// children, to avoid "too many connections" error in a common setup
static Sys_var_ulong Sys_max_connections(
       "max_connections", "The number of simultaneous clients allowed",
       GLOBAL_VAR(max_connections), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, 100000), DEFAULT(151), BLOCK_SIZE(1), NO_MUTEX_GUARD,
       NOT_IN_BINLOG, ON_CHECK(0), ON_UPDATE(fix_max_connections));

static Sys_var_ulong Sys_max_connect_errors(
       "max_connect_errors",
       "If there is more than this number of interrupted connections from "
       "a host this host will be blocked from further connections",
       GLOBAL_VAR(max_connect_errors), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, ULONG_MAX), DEFAULT(MAX_CONNECT_ERRORS),
       BLOCK_SIZE(1));

static bool check_max_delayed_threads(sys_var *self, THD *thd, set_var *var)
{
  return var->type != OPT_GLOBAL &&
         var->save_result.ulonglong_value != 0 &&
         var->save_result.ulonglong_value !=
                           global_system_variables.max_insert_delayed_threads;
}

// Alias for max_delayed_threads
static Sys_var_ulong Sys_max_insert_delayed_threads(
       "max_insert_delayed_threads",
       "Don't start more than this number of threads to handle INSERT "
       "DELAYED statements. If set to zero INSERT DELAYED will be not used",
       SESSION_VAR(max_insert_delayed_threads),
       NO_CMD_LINE, VALID_RANGE(0, 16384), DEFAULT(20),
       BLOCK_SIZE(1), NO_MUTEX_GUARD, NOT_IN_BINLOG,
       ON_CHECK(check_max_delayed_threads), ON_UPDATE(fix_max_connections));

static Sys_var_ulong Sys_max_delayed_threads(
       "max_delayed_threads",
       "Don't start more than this number of threads to handle INSERT "
       "DELAYED statements. If set to zero INSERT DELAYED will be not used",
       SESSION_VAR(max_insert_delayed_threads),
       CMD_LINE(REQUIRED_ARG), VALID_RANGE(0, 16384), DEFAULT(20),
       BLOCK_SIZE(1), NO_MUTEX_GUARD, NOT_IN_BINLOG,
       ON_CHECK(check_max_delayed_threads), ON_UPDATE(fix_max_connections));

static Sys_var_ulong Sys_max_error_count(
       "max_error_count",
       "Max number of errors/warnings to store for a statement",
       SESSION_VAR(max_error_count), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, 65535), DEFAULT(DEFAULT_ERROR_COUNT), BLOCK_SIZE(1));

static Sys_var_ulonglong Sys_max_heap_table_size(
       "max_heap_table_size",
       "Don't allow creation of heap tables bigger than this",
       SESSION_VAR(max_heap_table_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(16384, (ulonglong)~(intptr)0), DEFAULT(16*1024*1024),
       BLOCK_SIZE(1024));

static Sys_var_ulong Sys_pseudo_thread_id(
       "pseudo_thread_id",
       "This variable is for internal server use",
       SESSION_ONLY(pseudo_thread_id),
       NO_CMD_LINE, VALID_RANGE(0, ULONG_MAX), DEFAULT(0),
       BLOCK_SIZE(1), NO_MUTEX_GUARD, IN_BINLOG,
       ON_CHECK(check_has_super));

static bool fix_max_join_size(sys_var *self, THD *thd, enum_var_type type)
{
  SV *sv= type == OPT_GLOBAL ? &global_system_variables : &thd->variables;
  if (sv->max_join_size == HA_POS_ERROR)
    sv->option_bits|= OPTION_BIG_SELECTS;
  else
    sv->option_bits&= ~OPTION_BIG_SELECTS;
  return false;
}
static Sys_var_harows Sys_max_join_size(
       "max_join_size",
       "Joins that are probably going to read more than max_join_size "
       "records return an error",
       SESSION_VAR(max_join_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, HA_POS_ERROR), DEFAULT(HA_POS_ERROR), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_max_join_size));

static Sys_var_ulong Sys_max_seeks_for_key(
       "max_seeks_for_key",
       "Limit assumed max number of seeks when looking up rows based on a key",
       SESSION_VAR(max_seeks_for_key), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, ULONG_MAX), DEFAULT(ULONG_MAX), BLOCK_SIZE(1));

static Sys_var_ulong Sys_max_length_for_sort_data(
       "max_length_for_sort_data",
       "Max number of bytes in sorted records",
       SESSION_VAR(max_length_for_sort_data), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(4, 8192*1024L), DEFAULT(1024), BLOCK_SIZE(1));

static Sys_var_harows Sys_sql_max_join_size(
       "sql_max_join_size", "Alias for max_join_size",
       SESSION_VAR(max_join_size), NO_CMD_LINE,
       VALID_RANGE(1, HA_POS_ERROR), DEFAULT(HA_POS_ERROR), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_max_join_size), DEPRECATED(70000, 0));

static PolyLock_mutex PLock_prepared_stmt_count(&LOCK_prepared_stmt_count);
static Sys_var_ulong Sys_max_prepared_stmt_count(
       "max_prepared_stmt_count",
       "Maximum number of prepared statements in the server",
       GLOBAL_VAR(max_prepared_stmt_count), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, 1024*1024), DEFAULT(16382), BLOCK_SIZE(1),
       &PLock_prepared_stmt_count);

static bool fix_max_relay_log_size(sys_var *self, THD *thd, enum_var_type type)
{
#ifdef HAVE_REPLICATION
  active_mi->rli.relay_log.set_max_size(max_relay_log_size ?
                                        max_relay_log_size: max_binlog_size);
#endif
  return false;
}
static Sys_var_ulong Sys_max_relay_log_size(
       "max_relay_log_size",
       "If non-zero: relay log will be rotated automatically when the "
       "size exceeds this value; if zero: when the size "
       "exceeds max_binlog_size",
       GLOBAL_VAR(max_relay_log_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, 1024L*1024*1024), DEFAULT(0), BLOCK_SIZE(IO_SIZE),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_max_relay_log_size));

static Sys_var_ulong Sys_max_sort_length(
       "max_sort_length",
       "The number of bytes to use when sorting BLOB or TEXT values (only "
       "the first max_sort_length bytes of each value are used; the rest "
       "are ignored)",
       SESSION_VAR(max_sort_length), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(4, 8192*1024L), DEFAULT(1024), BLOCK_SIZE(1));

static Sys_var_ulong Sys_max_sp_recursion_depth(
       "max_sp_recursion_depth",
       "Maximum stored procedure recursion depth",
       SESSION_VAR(max_sp_recursion_depth), CMD_LINE(OPT_ARG),
       VALID_RANGE(0, 255), DEFAULT(0), BLOCK_SIZE(1));

// non-standard session_value_ptr() here
static Sys_var_max_user_conn Sys_max_user_connections(
       "max_user_connections",
       "The maximum number of active connections for a single user "
       "(0 = no limit)",
       SESSION_VAR(max_user_connections), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, UINT_MAX), DEFAULT(0), BLOCK_SIZE(1), NO_MUTEX_GUARD,
       NOT_IN_BINLOG, ON_CHECK(session_readonly));

static Sys_var_ulong Sys_max_tmp_tables(
       "max_tmp_tables",
       "Maximum number of temporary tables a client can keep open at a time",
       SESSION_VAR(max_tmp_tables), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, ULONG_MAX), DEFAULT(32), BLOCK_SIZE(1));

static Sys_var_ulong Sys_max_write_lock_count(
       "max_write_lock_count",
       "After this many write locks, allow some read locks to run in between",
       GLOBAL_VAR(max_write_lock_count), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, ULONG_MAX), DEFAULT(ULONG_MAX), BLOCK_SIZE(1));

static Sys_var_ulong Sys_min_examined_row_limit(
       "min_examined_row_limit",
       "Don't write queries to slow log that examine fewer rows "
       "than that",
       SESSION_VAR(min_examined_row_limit), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, ULONG_MAX), DEFAULT(0), BLOCK_SIZE(1));

#ifdef _WIN32
static Sys_var_mybool Sys_named_pipe(
       "named_pipe", "Enable the named pipe (NT)",
       READ_ONLY GLOBAL_VAR(opt_enable_named_pipe), CMD_LINE(OPT_ARG),
       DEFAULT(FALSE));
#endif

static Sys_var_ulong Sys_net_buffer_length(
       "net_buffer_length",
       "Buffer length for TCP/IP and socket communication",
       SESSION_VAR(net_buffer_length), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1024, 1024*1024), DEFAULT(16384), BLOCK_SIZE(1024),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(session_readonly));

static bool fix_net_read_timeout(sys_var *self, THD *thd, enum_var_type type)
{
  if (type != OPT_GLOBAL)
    my_net_set_read_timeout(&thd->net, thd->variables.net_read_timeout);
  return false;
}
static Sys_var_ulong Sys_net_read_timeout(
       "net_read_timeout",
       "Number of seconds to wait for more data from a connection before "
       "aborting the read",
       SESSION_VAR(net_read_timeout), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, LONG_TIMEOUT), DEFAULT(NET_READ_TIMEOUT), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_net_read_timeout));

static bool fix_net_write_timeout(sys_var *self, THD *thd, enum_var_type type)
{
  if (type != OPT_GLOBAL)
    my_net_set_write_timeout(&thd->net, thd->variables.net_write_timeout);
  return false;
}
static Sys_var_ulong Sys_net_write_timeout(
       "net_write_timeout",
       "Number of seconds to wait for a block to be written to a connection "
       "before aborting the write",
       SESSION_VAR(net_write_timeout), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, LONG_TIMEOUT), DEFAULT(NET_WRITE_TIMEOUT), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_net_write_timeout));

static bool fix_net_retry_count(sys_var *self, THD *thd, enum_var_type type)
{
  if (type != OPT_GLOBAL)
    thd->net.retry_count=thd->variables.net_retry_count;
  return false;
}
static Sys_var_ulong Sys_net_retry_count(
       "net_retry_count",
       "If a read on a communication port is interrupted, retry this "
       "many times before giving up",
       SESSION_VAR(net_retry_count), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, ULONG_MAX), DEFAULT(MYSQLD_NET_RETRY_COUNT),
       BLOCK_SIZE(1), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_net_retry_count));

static Sys_var_mybool Sys_new_mode(
       "new", "Use very new possible \"unsafe\" functions",
       SESSION_VAR(new_mode), CMD_LINE(OPT_ARG, 'n'), DEFAULT(FALSE));

static Sys_var_mybool Sys_old_mode(
       "old", "Use compatible behavior",
       READ_ONLY GLOBAL_VAR(old_mode), CMD_LINE(OPT_ARG), DEFAULT(FALSE));

static Sys_var_mybool Sys_old_alter_table(
       "old_alter_table", "Use old, non-optimized alter table",
       SESSION_VAR(old_alter_table), CMD_LINE(OPT_ARG), DEFAULT(FALSE));

static bool check_old_passwords(sys_var *self, THD *thd, set_var *var)
{
  return mysql_user_table_is_in_short_password_format;
}
static Sys_var_mybool Sys_old_passwords(
       "old_passwords",
       "Use old password encryption method (needed for 4.0 and older clients)",
       SESSION_VAR(old_passwords), CMD_LINE(OPT_ARG), DEFAULT(FALSE),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(check_old_passwords));

static Sys_var_ulong Sys_open_files_limit(
       "open_files_limit",
       "If this is not 0, then mysqld will use this value to reserve file "
       "descriptors to use with setrlimit(). If this value is 0 then mysqld "
       "will reserve max_connections*5 or max_connections + table_cache*2 "
       "(whichever is larger) number of file descriptors",
       READ_ONLY GLOBAL_VAR(open_files_limit), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, OS_FILE_LIMIT), DEFAULT(0), BLOCK_SIZE(1));

/// @todo change to enum
static Sys_var_ulong Sys_optimizer_prune_level(
       "optimizer_prune_level",
       "Controls the heuristic(s) applied during query optimization to prune "
       "less-promising partial plans from the optimizer search space. "
       "Meaning: 0 - do not apply any heuristic, thus perform exhaustive "
       "search; 1 - prune plans based on number of retrieved rows",
       SESSION_VAR(optimizer_prune_level), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, 1), DEFAULT(1), BLOCK_SIZE(1));

static Sys_var_ulong Sys_optimizer_search_depth(
       "optimizer_search_depth",
       "Maximum depth of search performed by the query optimizer. Values "
       "larger than the number of relations in a query result in better "
       "query plans, but take longer to compile a query. Values smaller "
       "than the number of tables in a relation result in faster "
       "optimization, but may produce very bad query plans. If set to 0, "
       "the system will automatically pick a reasonable value; if set to "
       "63, the optimizer will switch to the original find_best search"
       "(used for testing/comparison)",
       SESSION_VAR(optimizer_search_depth), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, MAX_TABLES+2), DEFAULT(MAX_TABLES+1), BLOCK_SIZE(1));

static const char *optimizer_switch_names[]=
{
  "index_merge", "index_merge_union", "index_merge_sort_union",
  "index_merge_intersection",
  "default", NullS
};
static Sys_var_flagset Sys_optimizer_switch(
       "optimizer_switch",
       "optimizer_switch=option=val[,option=val...], where option is one of "
       "{index_merge, index_merge_union, index_merge_sort_union, "
       "index_merge_intersection} and val is one of {on, off, default}",
       SESSION_VAR(optimizer_switch), CMD_LINE(REQUIRED_ARG),
       optimizer_switch_names, DEFAULT(OPTIMIZER_SWITCH_DEFAULT));

static Sys_var_charptr Sys_pid_file(
       "pid_file", "Pid file used by safe_mysqld",
       READ_ONLY GLOBAL_VAR(pidfile_name_ptr), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_charptr Sys_plugin_dir(
       "plugin_dir", "Directory for plugins",
       READ_ONLY GLOBAL_VAR(opt_plugin_dir_ptr), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_uint Sys_port(
       "port",
       "Port number to use for connection or 0 to default to, "
       "my.cnf, $MYSQL_TCP_PORT, "
#if MYSQL_PORT_DEFAULT == 0
       "/etc/services, "
#endif
       "built-in default (" STRINGIFY_ARG(MYSQL_PORT) "), whatever comes first",
       READ_ONLY GLOBAL_VAR(mysqld_port), CMD_LINE(REQUIRED_ARG, 'P'),
       VALID_RANGE(0, UINT_MAX32), DEFAULT(0), BLOCK_SIZE(1));

static Sys_var_ulong Sys_preload_buff_size(
       "preload_buffer_size",
       "The size of the buffer that is allocated when preloading indexes",
       SESSION_VAR(preload_buff_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1024, 1024*1024*1024), DEFAULT(32768), BLOCK_SIZE(1));

static Sys_var_uint Sys_protocol_version(
       "protocol_version",
       "The version of the client/server protocol used by the MySQL server",
       READ_ONLY GLOBAL_VAR(protocol_version), NO_CMD_LINE,
       VALID_RANGE(0, ~0), DEFAULT(PROTOCOL_VERSION), BLOCK_SIZE(1));

static Sys_var_ulong Sys_read_buff_size(
       "read_buffer_size",
       "Each thread that does a sequential scan allocates a buffer of "
       "this size for each table it scans. If you do many sequential scans, "
       "you may want to increase this value",
       SESSION_VAR(read_buff_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(IO_SIZE*2, INT_MAX32), DEFAULT(128*1024),
       BLOCK_SIZE(IO_SIZE));

static my_bool read_only;
static bool check_read_only(sys_var *self, THD *thd, set_var *var)
{
  /* Prevent self dead-lock */
  if (thd->locked_tables_mode || thd->active_transaction())
  {
    my_error(ER_LOCK_OR_ACTIVE_TRANSACTION, MYF(0));
    return true;
  }
  return false;
}
static bool fix_read_only(sys_var *self, THD *thd, enum_var_type type)
{
  bool result= true;
  my_bool new_read_only= read_only; // make a copy before releasing a mutex
  DBUG_ENTER("sys_var_opt_readonly::update");

  if (read_only == FALSE || read_only == opt_readonly)
  {
    opt_readonly= read_only;
    DBUG_RETURN(false);
  }

  if (check_read_only(self, thd, 0)) // just in case
    goto end;

  if (thd->global_read_lock.is_acquired())
  {
    /*
      This connection already holds the global read lock.
      This can be the case with:
      - FLUSH TABLES WITH READ LOCK
      - SET GLOBAL READ_ONLY = 1
    */
    opt_readonly= read_only;
    DBUG_RETURN(false);
  }

  /*
    Perform a 'FLUSH TABLES WITH READ LOCK'.
    This is a 3 step process:
    - [1] lock_global_read_lock()
    - [2] close_cached_tables()
    - [3] make_global_read_lock_block_commit()
    [1] prevents new connections from obtaining tables locked for write.
    [2] waits until all existing connections close their tables.
    [3] prevents transactions from being committed.
  */

  read_only= opt_readonly;
  pthread_mutex_unlock(&LOCK_global_system_variables);

  if (thd->global_read_lock.lock_global_read_lock(thd))
    goto end_with_mutex_unlock;

  /*
    This call will be blocked by any connection holding a READ or WRITE lock.
    Ideally, we want to wait only for pending WRITE locks, but since:
    con 1> LOCK TABLE T FOR READ;
    con 2> LOCK TABLE T FOR WRITE; (blocked by con 1)
    con 3> SET GLOBAL READ ONLY=1; (blocked by con 2)
    can cause to wait on a read lock, it's required for the client application
    to unlock everything, and acceptable for the server to wait on all locks.
  */
  if ((result= close_cached_tables(thd, NULL, FALSE, TRUE)))
    goto end_with_read_lock;

  if ((result= thd->global_read_lock.make_global_read_lock_block_commit(thd)))
    goto end_with_read_lock;

  /* Change the opt_readonly system variable, safe because the lock is held */
  opt_readonly= new_read_only;
  result= false;

 end_with_read_lock:
  /* Release the lock */
  thd->global_read_lock.unlock_global_read_lock(thd);
 end_with_mutex_unlock:
  pthread_mutex_lock(&LOCK_global_system_variables);
 end:
  read_only= opt_readonly;
  DBUG_RETURN(result);
}
static Sys_var_mybool Sys_readonly(
       "read_only",
       "Make all non-temporary tables read-only, with the exception for "
       "replication (slave) threads and users with the SUPER privilege",
       GLOBAL_VAR(read_only), CMD_LINE(OPT_ARG), DEFAULT(FALSE),
       NO_MUTEX_GUARD, NOT_IN_BINLOG,
       ON_CHECK(check_read_only), ON_UPDATE(fix_read_only));

// Small lower limit to be able to test MRR
static Sys_var_ulong Sys_read_rnd_buff_size(
       "read_rnd_buffer_size",
       "When reading rows in sorted order after a sort, the rows are read "
       "through this buffer to avoid a disk seeks. If not set, then it's "
       "set to the value of record_buffer",
       SESSION_VAR(read_rnd_buff_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, INT_MAX32), DEFAULT(256*1024), BLOCK_SIZE(1));

static Sys_var_ulong Sys_div_precincrement(
       "div_precision_increment", "Precision of the result of '/' "
       "operator will be increased on that value",
       SESSION_VAR(div_precincrement), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, DECIMAL_MAX_SCALE), DEFAULT(4), BLOCK_SIZE(1));

static Sys_var_ulong Sys_rpl_recovery_rank(
       "rpl_recovery_rank", "Unused, will be removed",
       GLOBAL_VAR(rpl_recovery_rank), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, ULONG_MAX), DEFAULT(0), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0), ON_UPDATE(0),
       DEPRECATED(70000, 0));

static Sys_var_ulong Sys_range_alloc_block_size(
       "range_alloc_block_size",
       "Allocation block size for storing ranges during optimization",
       SESSION_VAR(range_alloc_block_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(RANGE_ALLOC_BLOCK_SIZE, ULONG_MAX),
       DEFAULT(RANGE_ALLOC_BLOCK_SIZE), BLOCK_SIZE(1024));

static Sys_var_ulong Sys_multi_range_count(
       "multi_range_count", "Number of key ranges to request at once",
       SESSION_VAR(multi_range_count), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, ULONG_MAX), DEFAULT(256), BLOCK_SIZE(1));

static bool fix_thd_mem_root(sys_var *self, THD *thd, enum_var_type type)
{
  if (type != OPT_GLOBAL)
    reset_root_defaults(thd->mem_root,
                        thd->variables.query_alloc_block_size,
                        thd->variables.query_prealloc_size);
  return false;
}
static Sys_var_ulong Sys_query_alloc_block_size(
       "query_alloc_block_size",
       "Allocation block size for query parsing and execution",
       SESSION_VAR(query_alloc_block_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1024, ULONG_MAX), DEFAULT(QUERY_ALLOC_BLOCK_SIZE),
       BLOCK_SIZE(1024), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_thd_mem_root));

static Sys_var_ulong Sys_query_prealloc_size(
       "query_prealloc_size",
       "Persistent buffer for query parsing and execution",
       SESSION_VAR(query_prealloc_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(QUERY_ALLOC_PREALLOC_SIZE, ULONG_MAX),
       DEFAULT(QUERY_ALLOC_PREALLOC_SIZE),
       BLOCK_SIZE(1024), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_thd_mem_root));

#ifdef HAVE_SMEM
static Sys_var_mybool Sys_shared_memory(
       "shared_memory", "Enable the shared memory",
       READ_ONLY GLOBAL_VAR(opt_enable_shared_memory), CMD_LINE(OPT_ARG),
       DEFAULT(FALSE));

static Sys_var_charptr Sys_shared_memory_base_name(
       "shared_memory_base_name", "Base name of shared memory",
       READ_ONLY GLOBAL_VAR(shared_memory_base_name), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0));
#endif

// this has to be NO_CMD_LINE as the command-line option has a different name
static Sys_var_mybool Sys_skip_external_locking(
       "skip_external_locking", "Don't use system (external) locking",
       READ_ONLY GLOBAL_VAR(my_disable_locking), NO_CMD_LINE, DEFAULT(TRUE));

static Sys_var_mybool Sys_skip_networking(
       "skip_networking", "Don't allow connection with TCP/IP",
       READ_ONLY GLOBAL_VAR(opt_disable_networking), CMD_LINE(OPT_ARG),
       DEFAULT(FALSE));

static Sys_var_mybool Sys_skip_show_database(
       "skip_show_database", "Don't allow 'SHOW DATABASE' commands",
       READ_ONLY GLOBAL_VAR(opt_skip_show_db), CMD_LINE(OPT_ARG),
       DEFAULT(FALSE));

static Sys_var_charptr Sys_socket(
       "socket", "Socket file to use for connection",
       READ_ONLY GLOBAL_VAR(mysqld_unix_port), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0));

#ifdef HAVE_THR_SETCONCURRENCY
static Sys_var_ulong Sys_thread_concurrency(
       "thread_concurrency",
       "Permits the application to give the threads system a hint for "
       "the desired number of threads that should be run at the same time",
       READ_ONLY GLOBAL_VAR(concurrency), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, 512), DEFAULT(DEFAULT_CONCURRENCY), BLOCK_SIZE(1));
#endif

static Sys_var_ulong Sys_thread_stack(
       "thread_stack", "The stack size for each thread",
       READ_ONLY GLOBAL_VAR(my_thread_stack_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(128*1024, ULONG_MAX), DEFAULT(DEFAULT_THREAD_STACK),
       BLOCK_SIZE(1024));

static Sys_var_charptr Sys_tmpdir(
       "tmpdir", "Path for temporary files. Several paths may "
       "be specified, separated by a "
#if defined(__WIN__) || defined(__NETWARE__)
       "semicolon (;)"
#else
       "colon (:)"
#endif
       ", in this case they are used in a round-robin fashion",
       READ_ONLY GLOBAL_VAR(opt_mysql_tmpdir), CMD_LINE(REQUIRED_ARG, 't'),
       IN_FS_CHARSET, DEFAULT(0));

static bool fix_trans_mem_root(sys_var *self, THD *thd, enum_var_type type)
{
  if (type != OPT_GLOBAL)
    reset_root_defaults(&thd->transaction.mem_root,
                        thd->variables.trans_alloc_block_size,
                        thd->variables.trans_prealloc_size);
  return false;
}
static Sys_var_ulong Sys_trans_alloc_block_size(
       "transaction_alloc_block_size",
       "Allocation block size for transactions to be stored in binary log",
       SESSION_VAR(trans_alloc_block_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1024, ULONG_MAX), DEFAULT(QUERY_ALLOC_BLOCK_SIZE),
       BLOCK_SIZE(1024), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_trans_mem_root));

static Sys_var_ulong Sys_trans_prealloc_size(
       "transaction_prealloc_size",
       "Persistent buffer for transactions to be stored in binary log",
       SESSION_VAR(trans_prealloc_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1024, ULONG_MAX), DEFAULT(TRANS_ALLOC_PREALLOC_SIZE),
       BLOCK_SIZE(1024), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_trans_mem_root));

static const char *thread_handling_names[]=
{
  "one-thread-per-connection", "no-threads",
#if HAVE_POOL_OF_THREADS == 1
  "pool-of-threads",
#endif
  0
};
static Sys_var_enum Sys_thread_handling(
       "thread_handling",
       "Define threads usage for handling queries, one of "
       "one-thread-per-connection, no-threads"
#if HAVE_POOL_OF_THREADS == 1
       ", pool-of-threads"
#endif
       , READ_ONLY GLOBAL_VAR(thread_handling), CMD_LINE(REQUIRED_ARG),
       thread_handling_names, DEFAULT(0));

#ifdef HAVE_QUERY_CACHE
static bool fix_query_cache_size(sys_var *self, THD *thd, enum_var_type type)
{
  ulong new_cache_size= query_cache.resize(query_cache_size);
  /*
     Note: query_cache_size is a global variable reflecting the
     requested cache size. See also query_cache_size_arg
  */
  if (query_cache_size != new_cache_size)
    push_warning_printf(current_thd, MYSQL_ERROR::WARN_LEVEL_WARN,
                        ER_WARN_QC_RESIZE, ER(ER_WARN_QC_RESIZE),
                        query_cache_size, new_cache_size);

  query_cache_size= new_cache_size;
  return false;
}
static Sys_var_ulong Sys_query_cache_size(
       "query_cache_size",
       "The memory allocated to store results from old queries",
       GLOBAL_VAR(query_cache_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, ULONG_MAX), DEFAULT(0), BLOCK_SIZE(1024),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_query_cache_size));

static Sys_var_ulong Sys_query_cache_limit(
       "query_cache_limit",
       "Don't cache results that are bigger than this",
       GLOBAL_VAR(query_cache.query_cache_limit), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, ULONG_MAX), DEFAULT(1024*1024), BLOCK_SIZE(1));

static bool fix_qcache_min_res_unit(sys_var *self, THD *thd, enum_var_type type)
{
  query_cache_min_res_unit=
    query_cache.set_min_res_unit(query_cache_min_res_unit);
  return false;
}
static Sys_var_ulong Sys_query_cache_min_res_unit(
       "query_cache_min_res_unit",
       "The minimum size for blocks allocated by the query cache",
       GLOBAL_VAR(query_cache_min_res_unit), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, ULONG_MAX), DEFAULT(QUERY_CACHE_MIN_RESULT_DATA_SIZE),
       BLOCK_SIZE(1), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_qcache_min_res_unit));

static const char *query_cache_type_names[]= { "OFF", "ON", "DEMAND", 0 };
static bool check_query_cache_type(sys_var *self, THD *thd, set_var *var)
{
  if (query_cache.is_disabled())
  {
    my_error(ER_QUERY_CACHE_DISABLED, MYF(0));
    return true;
  }
  return false;
}
static Sys_var_enum Sys_query_cache_type(
       "query_cache_type",
       "OFF = Don't cache or retrieve results. ON = Cache all results "
       "except SELECT SQL_NO_CACHE ... queries. DEMAND = Cache only "
       "SELECT SQL_CACHE ... queries",
       SESSION_VAR(query_cache_type), CMD_LINE(REQUIRED_ARG),
       query_cache_type_names, DEFAULT(1), NO_MUTEX_GUARD, NOT_IN_BINLOG,
       ON_CHECK(check_query_cache_type));

static Sys_var_mybool Sys_query_cache_wlock_invalidate(
       "query_cache_wlock_invalidate",
       "Invalidate queries in query cache on LOCK for write",
       SESSION_VAR(query_cache_wlock_invalidate), CMD_LINE(OPT_ARG),
       DEFAULT(FALSE));
#endif /* HAVE_QUERY_CACHE */

static Sys_var_mybool Sys_secure_auth(
       "secure_auth",
       "Disallow authentication for accounts that have old (pre-4.1) "
       "passwords",
       GLOBAL_VAR(opt_secure_auth), CMD_LINE(OPT_ARG),
       DEFAULT(FALSE));

static Sys_var_charptr Sys_secure_file_priv(
       "secure_file_priv",
       "Limit LOAD DATA, SELECT ... OUTFILE, and LOAD_FILE() to files "
       "within specified directory",
       PREALLOCATED READ_ONLY GLOBAL_VAR(opt_secure_file_priv),
       CMD_LINE(REQUIRED_ARG), IN_FS_CHARSET, DEFAULT(0));

static bool fix_server_id(sys_var *self, THD *thd, enum_var_type type)
{
  server_id_supplied = 1;
  thd->server_id= server_id;
  return false;
}
static Sys_var_ulong Sys_server_id(
       "server_id",
       "Uniquely identifies the server instance in the community of "
       "replication partners",
       GLOBAL_VAR(server_id), CMD_LINE(REQUIRED_ARG, OPT_SERVER_ID),
       VALID_RANGE(0, UINT_MAX32), DEFAULT(0), BLOCK_SIZE(1), NO_MUTEX_GUARD,
       NOT_IN_BINLOG, ON_CHECK(0), ON_UPDATE(fix_server_id));

static Sys_var_mybool Sys_slave_compressed_protocol(
       "slave_compressed_protocol",
       "Use compression on master/slave protocol",
       GLOBAL_VAR(opt_slave_compressed_protocol), CMD_LINE(OPT_ARG),
       DEFAULT(FALSE));

#ifdef HAVE_REPLICATION
static const char *slave_exec_mode_names[]= {"STRICT", "IDEMPOTENT", 0};
static Sys_var_enum Slave_exec_mode(
       "slave_exec_mode",
       "Modes for how replication events should be executed. Legal values "
       "are STRICT (default) and IDEMPOTENT. In IDEMPOTENT mode, "
       "replication will not stop for operations that are idempotent. "
       "In STRICT mode, replication will stop on any unexpected difference "
       "between the master and the slave",
       GLOBAL_VAR(slave_exec_mode_options), CMD_LINE(REQUIRED_ARG),
       slave_exec_mode_names, DEFAULT(SLAVE_EXEC_MODE_STRICT));
#endif

static Sys_var_ulong Sys_slow_launch_time(
       "slow_launch_time",
       "If creating the thread takes longer than this value (in seconds), "
       "the Slow_launch_threads counter will be incremented",
       GLOBAL_VAR(slow_launch_time), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, LONG_TIMEOUT), DEFAULT(2), BLOCK_SIZE(1));

static Sys_var_ulong Sys_sort_buffer(
       "sort_buffer_size",
       "Each thread that needs to do a sort allocates a buffer of this size",
       SESSION_VAR(sortbuff_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(MIN_SORT_MEMORY, ULONG_MAX), DEFAULT(MAX_SORT_MEMORY),
       BLOCK_SIZE(1));

export ulong expand_sql_mode(ulonglong sql_mode)
{
  if (sql_mode & MODE_ANSI)
  {
    /*
      Note that we dont set
      MODE_NO_KEY_OPTIONS | MODE_NO_TABLE_OPTIONS | MODE_NO_FIELD_OPTIONS
      to allow one to get full use of MySQL in this mode.

      MODE_ONLY_FULL_GROUP_BY was removed from ANSI mode because it is
      currently overly restrictive (see BUG#8510).
    */
    sql_mode|= (MODE_REAL_AS_FLOAT | MODE_PIPES_AS_CONCAT | MODE_ANSI_QUOTES |
                MODE_IGNORE_SPACE);
  }
  if (sql_mode & MODE_ORACLE)
    sql_mode|= (MODE_PIPES_AS_CONCAT | MODE_ANSI_QUOTES |
                MODE_IGNORE_SPACE |
                MODE_NO_KEY_OPTIONS | MODE_NO_TABLE_OPTIONS |
                MODE_NO_FIELD_OPTIONS | MODE_NO_AUTO_CREATE_USER);
  if (sql_mode & MODE_MSSQL)
    sql_mode|= (MODE_PIPES_AS_CONCAT | MODE_ANSI_QUOTES |
                MODE_IGNORE_SPACE |
                MODE_NO_KEY_OPTIONS | MODE_NO_TABLE_OPTIONS |
                MODE_NO_FIELD_OPTIONS);
  if (sql_mode & MODE_POSTGRESQL)
    sql_mode|= (MODE_PIPES_AS_CONCAT | MODE_ANSI_QUOTES |
                MODE_IGNORE_SPACE |
                MODE_NO_KEY_OPTIONS | MODE_NO_TABLE_OPTIONS |
                MODE_NO_FIELD_OPTIONS);
  if (sql_mode & MODE_DB2)
    sql_mode|= (MODE_PIPES_AS_CONCAT | MODE_ANSI_QUOTES |
                MODE_IGNORE_SPACE |
                MODE_NO_KEY_OPTIONS | MODE_NO_TABLE_OPTIONS |
                MODE_NO_FIELD_OPTIONS);
  if (sql_mode & MODE_MAXDB)
    sql_mode|= (MODE_PIPES_AS_CONCAT | MODE_ANSI_QUOTES |
                MODE_IGNORE_SPACE |
                MODE_NO_KEY_OPTIONS | MODE_NO_TABLE_OPTIONS |
                MODE_NO_FIELD_OPTIONS | MODE_NO_AUTO_CREATE_USER);
  if (sql_mode & MODE_MYSQL40)
    sql_mode|= MODE_HIGH_NOT_PRECEDENCE;
  if (sql_mode & MODE_MYSQL323)
    sql_mode|= MODE_HIGH_NOT_PRECEDENCE;
  if (sql_mode & MODE_TRADITIONAL)
    sql_mode|= (MODE_STRICT_TRANS_TABLES | MODE_STRICT_ALL_TABLES |
                MODE_NO_ZERO_IN_DATE | MODE_NO_ZERO_DATE |
                MODE_ERROR_FOR_DIVISION_BY_ZERO | MODE_NO_AUTO_CREATE_USER |
                MODE_NO_ENGINE_SUBSTITUTION);
  return sql_mode;
}
static bool check_sql_mode(sys_var *self, THD *thd, set_var *var)
{
  var->save_result.ulonglong_value=
    expand_sql_mode(var->save_result.ulonglong_value);
  return false;
}
static bool fix_sql_mode(sys_var *self, THD *thd, enum_var_type type)
{
  if (type != OPT_GLOBAL)
  {
    /* Update thd->server_status */
    if (thd->variables.sql_mode & MODE_NO_BACKSLASH_ESCAPES)
      thd->server_status|= SERVER_STATUS_NO_BACKSLASH_ESCAPES;
    else
      thd->server_status&= ~SERVER_STATUS_NO_BACKSLASH_ESCAPES;
  }
  return false;
}
/*
  WARNING: When adding new SQL modes don't forget to update the
  tables definitions that stores it's value (ie: mysql.event, mysql.proc)
*/
static const char *sql_mode_names[]=
{
  "REAL_AS_FLOAT", "PIPES_AS_CONCAT", "ANSI_QUOTES", "IGNORE_SPACE", ",",
  "ONLY_FULL_GROUP_BY", "NO_UNSIGNED_SUBTRACTION", "NO_DIR_IN_CREATE",
  "POSTGRESQL", "ORACLE", "MSSQL", "DB2", "MAXDB", "NO_KEY_OPTIONS",
  "NO_TABLE_OPTIONS", "NO_FIELD_OPTIONS", "MYSQL323", "MYSQL40", "ANSI",
  "NO_AUTO_VALUE_ON_ZERO", "NO_BACKSLASH_ESCAPES", "STRICT_TRANS_TABLES",
  "STRICT_ALL_TABLES", "NO_ZERO_IN_DATE", "NO_ZERO_DATE",
  "ALLOW_INVALID_DATES", "ERROR_FOR_DIVISION_BY_ZERO", "TRADITIONAL",
  "NO_AUTO_CREATE_USER", "HIGH_NOT_PRECEDENCE", "NO_ENGINE_SUBSTITUTION",
  "PAD_CHAR_TO_FULL_LENGTH",
  0
};
export bool sql_mode_string_representation(THD *thd, ulong sql_mode,
                                           LEX_STRING *ls)
{
  set_to_string(thd, ls, sql_mode, sql_mode_names);
  return ls->str == 0;
}
/*
  sql_mode should *not* be IN_BINLOG: even though it is written to the binlog,
  the slave ignores the MODE_NO_DIR_IN_CREATE variable, so slave's value
  differs from master's (see log_event.cc: Query_log_event::do_apply_event()).
*/
static Sys_var_set Sys_sql_mode(
       "sql_mode",
       "Syntax: sql-mode=mode[,mode[,mode...]]. See the manual for the "
       "complete list of valid sql modes",
       SESSION_VAR(sql_mode), CMD_LINE(REQUIRED_ARG),
       sql_mode_names, DEFAULT(0), NO_MUTEX_GUARD, NOT_IN_BINLOG,
       ON_CHECK(check_sql_mode), ON_UPDATE(fix_sql_mode));

#ifdef HAVE_OPENSSL
#define SSL_OPT(X) CMD_LINE(REQUIRED_ARG,X)
#else
#define SSL_OPT(X) NO_CMD_LINE
#endif

static Sys_var_charptr Sys_ssl_ca(
       "ssl_ca",
       "CA file in PEM format (check OpenSSL docs, implies --ssl)",
       READ_ONLY GLOBAL_VAR(opt_ssl_ca), SSL_OPT(OPT_SSL_CA),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_charptr Sys_ssl_capath(
       "ssl_capath",
       "CA directory (check OpenSSL docs, implies --ssl)",
       READ_ONLY GLOBAL_VAR(opt_ssl_capath), SSL_OPT(OPT_SSL_CAPATH),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_charptr Sys_ssl_cert(
       "ssl_cert", "X509 cert in PEM format (implies --ssl)",
       READ_ONLY GLOBAL_VAR(opt_ssl_cert), SSL_OPT(OPT_SSL_CERT),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_charptr Sys_ssl_cipher(
       "ssl_cipher", "SSL cipher to use (implies --ssl)",
       READ_ONLY GLOBAL_VAR(opt_ssl_cipher), SSL_OPT(OPT_SSL_CIPHER),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_charptr Sys_ssl_key(
       "ssl_key", "X509 key in PEM format (implies --ssl)",
       READ_ONLY GLOBAL_VAR(opt_ssl_key), SSL_OPT(OPT_SSL_KEY),
       IN_FS_CHARSET, DEFAULT(0));

// why ENUM and not BOOL ?
static const char *updatable_views_with_limit_names[]= {"NO", "YES", 0};
static Sys_var_enum Sys_updatable_views_with_limit(
       "updatable_views_with_limit",
       "YES = Don't issue an error message (warning only) if a VIEW without "
       "presence of a key of the underlying table is used in queries with a "
       "LIMIT clause for updating. NO = Prohibit update of a VIEW, which "
       "does not contain a key of the underlying table and the query uses "
       "a LIMIT clause (usually get from GUI tools)",
       SESSION_VAR(updatable_views_with_limit), CMD_LINE(REQUIRED_ARG),
       updatable_views_with_limit_names, DEFAULT(TRUE));

static Sys_var_mybool Sys_sync_frm(
       "sync_frm", "Sync .frm files to disk on creation",
       GLOBAL_VAR(opt_sync_frm), CMD_LINE(OPT_ARG),
       DEFAULT(TRUE));

static char *system_time_zone_ptr;
static Sys_var_charptr Sys_system_time_zone(
       "system_time_zone", "The server system time zone",
       READ_ONLY GLOBAL_VAR(system_time_zone_ptr), NO_CMD_LINE,
       IN_FS_CHARSET, DEFAULT(system_time_zone));

static Sys_var_ulong Sys_table_def_size(
       "table_definition_cache",
       "The number of cached table definitions",
       GLOBAL_VAR(table_def_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(TABLE_DEF_CACHE_MIN, 512*1024),
       DEFAULT(TABLE_DEF_CACHE_DEFAULT), BLOCK_SIZE(1));

static Sys_var_ulong Sys_table_cache_size(
       "table_open_cache", "The number of cached open tables",
       GLOBAL_VAR(table_cache_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, 512*1024), DEFAULT(TABLE_OPEN_CACHE_DEFAULT),
       BLOCK_SIZE(1));

static Sys_var_ulong Sys_table_lock_wait_timeout(
       "table_lock_wait_timeout",
       "Timeout in seconds to wait for a table level lock before returning an "
       "error. Used only if the connection has active cursors",
       GLOBAL_VAR(table_lock_wait_timeout), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, 1024*1024*1024), DEFAULT(50), BLOCK_SIZE(1));

static Sys_var_ulong Sys_thread_cache_size(
       "thread_cache_size",
       "How many threads we should keep in a cache for reuse",
       GLOBAL_VAR(thread_cache_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, 16384), DEFAULT(0), BLOCK_SIZE(1));

#if HAVE_POOL_OF_THREADS == 1
static Sys_var_ulong Sys_thread_pool_size(
       "thread_pool_size",
       "How many threads we should create to handle query requests in "
       "case of 'thread_handling=pool-of-threads'",
       GLOBAL_VAR(thread_pool_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, 16384), DEFAULT(20), BLOCK_SIZE(0));
#endif

//  Can't change the 'next' tx_isolation if we are already in a transaction
static bool check_tx_isolation(sys_var *self, THD *thd, set_var *var)
{
  if (var->type == OPT_DEFAULT && (thd->server_status & SERVER_STATUS_IN_TRANS))
  {
    my_error(ER_CANT_CHANGE_TX_ISOLATION, MYF(0));
    return true;
  }
  return false;
}

/*
  If one doesn't use the SESSION modifier, the isolation level
  is only active for the next command.
*/
static bool fix_tx_isolation(sys_var *self, THD *thd, enum_var_type type)
{
  if (type == OPT_SESSION)
    thd->session_tx_isolation= (enum_tx_isolation)thd->variables.tx_isolation;
  return false;
}
// NO_CMD_LINE - different name of the option
static Sys_var_enum Sys_tx_isolation(
       "tx_isolation", "Default transaction isolation level",
       SESSION_VAR(tx_isolation), NO_CMD_LINE,
       tx_isolation_names, DEFAULT(ISO_REPEATABLE_READ),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(check_tx_isolation),
       ON_UPDATE(fix_tx_isolation));

static Sys_var_ulonglong Sys_tmp_table_size(
       "tmp_table_size",
       "If an internal in-memory temporary table exceeds this size, MySQL "
       "will automatically convert it to an on-disk MyISAM table",
       SESSION_VAR(tmp_table_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1024, (ulonglong)~(intptr)0), DEFAULT(16*1024*1024),
       BLOCK_SIZE(1));

static Sys_var_mybool Sys_timed_mutexes(
       "timed_mutexes",
       "Specify whether to time mutexes (only InnoDB mutexes are currently "
       "supported)",
       GLOBAL_VAR(timed_mutexes), CMD_LINE(OPT_ARG), DEFAULT(0));

static char *server_version_ptr;
static Sys_var_charptr Sys_version(
       "version", "Server version",
       READ_ONLY GLOBAL_VAR(server_version_ptr), NO_CMD_LINE,
       IN_SYSTEM_CHARSET, DEFAULT(server_version));

static char *server_version_comment_ptr;
static Sys_var_charptr Sys_version_comment(
       "version_comment", "version_comment",
       READ_ONLY GLOBAL_VAR(server_version_comment_ptr), NO_CMD_LINE,
       IN_SYSTEM_CHARSET, DEFAULT(MYSQL_COMPILATION_COMMENT));

static char *server_version_compile_machine_ptr;
static Sys_var_charptr Sys_version_compile_machine(
       "version_compile_machine", "version_compile_machine",
       READ_ONLY GLOBAL_VAR(server_version_compile_machine_ptr), NO_CMD_LINE,
       IN_SYSTEM_CHARSET, DEFAULT(MACHINE_TYPE));

static char *server_version_compile_os_ptr;
static Sys_var_charptr Sys_version_compile_os(
       "version_compile_os", "version_compile_os",
       READ_ONLY GLOBAL_VAR(server_version_compile_os_ptr), NO_CMD_LINE,
       IN_SYSTEM_CHARSET, DEFAULT(SYSTEM_TYPE));

static Sys_var_ulong Sys_net_wait_timeout(
       "wait_timeout",
       "The number of seconds the server waits for activity on a "
       "connection before closing it",
       SESSION_VAR(net_wait_timeout), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, IF_WIN(INT_MAX32/1000, LONG_TIMEOUT)),
       DEFAULT(NET_WAIT_TIMEOUT), BLOCK_SIZE(1));

static Sys_var_mybool Sys_engine_condition_pushdown(
       "engine_condition_pushdown",
       "Push supported query conditions to the storage engine",
       SESSION_VAR(engine_condition_pushdown), CMD_LINE(OPT_ARG),
       DEFAULT(TRUE));

static Sys_var_plugin Sys_default_storage_engine(
       "default_storage_engine", "The default storage engine for new tables",
       SESSION_VAR(table_plugin), NO_CMD_LINE,
       MYSQL_STORAGE_ENGINE_PLUGIN, DEFAULT(&default_storage_engine),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(check_not_null));

//  Alias for @@default_storage_engine
static Sys_var_plugin Sys_storage_engine(
       "storage_engine", "Alias for @@default_storage_engine. Deprecated",
       SESSION_VAR(table_plugin), NO_CMD_LINE,
       MYSQL_STORAGE_ENGINE_PLUGIN, DEFAULT(&default_storage_engine),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(check_not_null));

#if defined(ENABLED_DEBUG_SYNC)
/*
  Variable can be set for the session only.

  This could be changed later. Then we need to have a global array of
  actions in addition to the thread local ones. SET GLOBAL would
  manage the global array, SET [SESSION] the local array. A sync point
  would need to look for a local and a global action. Setting and
  executing of global actions need to be protected by a mutex.

  The purpose of global actions could be to allow synchronizing with
  connectionless threads that cannot execute SET statements.
*/
static Sys_var_debug_sync Sys_debug_sync(
       "debug_sync", "Debug Sync Facility",
       sys_var::ONLY_SESSION, NO_CMD_LINE,
       DEFAULT(0), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(check_has_super));
#endif /* defined(ENABLED_DEBUG_SYNC) */

/**
 "time_format" "date_format" "datetime_format"

  the following three variables are unused, and the source of confusion
  (bug reports like "I've changed date_format, but date format hasn't changed.
  I've made them read-only, to alleviate the situation somewhat.

  @todo make them NO_CMD_LINE ?
*/
static Sys_var_charptr Sys_date_format(
       "date_format", "The DATE format (ignored)",
       READ_ONLY GLOBAL_VAR(global_date_format.format.str),
       CMD_LINE(REQUIRED_ARG), IN_SYSTEM_CHARSET,
       DEFAULT(known_date_time_formats[ISO_FORMAT].date_format));

static Sys_var_charptr Sys_datetime_format(
       "datetime_format", "The DATETIME format (ignored)",
       READ_ONLY GLOBAL_VAR(global_datetime_format.format.str),
       CMD_LINE(REQUIRED_ARG), IN_SYSTEM_CHARSET,
       DEFAULT(known_date_time_formats[ISO_FORMAT].datetime_format));

static Sys_var_charptr Sys_time_format(
       "time_format", "The TIME format (ignored)",
       READ_ONLY GLOBAL_VAR(global_time_format.format.str),
       CMD_LINE(REQUIRED_ARG), IN_SYSTEM_CHARSET,
       DEFAULT(known_date_time_formats[ISO_FORMAT].time_format));

static bool fix_autocommit(sys_var *self, THD *thd, enum_var_type type)
{
  if (type == OPT_GLOBAL)
  {
    if (global_system_variables.option_bits & OPTION_AUTOCOMMIT)
      global_system_variables.option_bits&= ~OPTION_NOT_AUTOCOMMIT;
    else
      global_system_variables.option_bits|= OPTION_NOT_AUTOCOMMIT;
    return false;
  }

  if (thd->variables.option_bits & OPTION_AUTOCOMMIT &&
      thd->variables.option_bits & OPTION_NOT_AUTOCOMMIT)
  { // activating autocommit

    if (trans_commit(thd))
    {
      thd->variables.option_bits&= ~OPTION_AUTOCOMMIT;
      return true;
    }
    close_thread_tables(thd);
    thd->mdl_context.release_transactional_locks();

    thd->variables.option_bits&=
                 ~(OPTION_BEGIN | OPTION_KEEP_LOG | OPTION_NOT_AUTOCOMMIT);
    thd->transaction.all.modified_non_trans_table= false;
    thd->server_status|= SERVER_STATUS_AUTOCOMMIT;
    return false;
  }

  if (!(thd->variables.option_bits & OPTION_AUTOCOMMIT) &&
      !(thd->variables.option_bits & OPTION_NOT_AUTOCOMMIT))
  { // disabling autocommit

    thd->transaction.all.modified_non_trans_table= false;
    thd->server_status&= ~SERVER_STATUS_AUTOCOMMIT;
    thd->variables.option_bits|= OPTION_NOT_AUTOCOMMIT;
    return false;
  }

  return false; // autocommit value wasn't changed
}
static Sys_var_bit Sys_autocommit(
       "autocommit", "autocommit",
       SESSION_VAR(option_bits), NO_CMD_LINE, OPTION_AUTOCOMMIT, DEFAULT(TRUE),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0), ON_UPDATE(fix_autocommit));
export sys_var *Sys_autocommit_ptr= &Sys_autocommit; // for sql_yacc.yy

static Sys_var_mybool Sys_big_tables(
       "big_tables", "Allow big result sets by saving all "
       "temporary sets on file (Solves most 'table full' errors)",
       SESSION_VAR(big_tables), CMD_LINE(OPT_ARG), DEFAULT(FALSE));

#ifndef TO_BE_DELETED   /* Alias for big_tables */
static Sys_var_mybool Sys_sql_big_tables(
       "sql_big_tables", "alias for big_tables",
       SESSION_VAR(big_tables), NO_CMD_LINE, DEFAULT(FALSE));
#endif

static Sys_var_bit Sys_big_selects(
       "sql_big_selects", "sql_big_selects",
       SESSION_VAR(option_bits), NO_CMD_LINE, OPTION_BIG_SELECTS,
       DEFAULT(FALSE));

static Sys_var_bit Sys_log_off(
       "sql_log_off", "sql_log_off",
       SESSION_VAR(option_bits), NO_CMD_LINE, OPTION_LOG_OFF,
       DEFAULT(FALSE), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(check_has_super));

static bool fix_sql_log_bin(sys_var *self, THD *thd, enum_var_type type)
{
  if (type != OPT_GLOBAL && !thd->in_sub_stmt)
    thd->sql_log_bin_toplevel= thd->variables.option_bits & OPTION_BIN_LOG;
  return false;
}
static Sys_var_bit Sys_log_binlog(
       "sql_log_bin", "sql_log_bin",
       SESSION_VAR(option_bits), NO_CMD_LINE, OPTION_BIN_LOG,
       DEFAULT(TRUE), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(check_has_super),
       ON_UPDATE(fix_sql_log_bin));

static bool deprecated_log_update(sys_var *self, THD *thd, set_var *var)
{
  /*
    The update log is not supported anymore since 5.0.
    See sql/mysqld.cc/, comments in function init_server_components() for an
    explaination of the different warnings we send below
  */

  if (opt_sql_bin_update)
    push_warning(thd, MYSQL_ERROR::WARN_LEVEL_NOTE,
                 ER_UPDATE_LOG_DEPRECATED_TRANSLATED,
                 ER(ER_UPDATE_LOG_DEPRECATED_TRANSLATED));
  else
    push_warning(thd, MYSQL_ERROR::WARN_LEVEL_NOTE,
                 ER_UPDATE_LOG_DEPRECATED_IGNORED,
                 ER(ER_UPDATE_LOG_DEPRECATED_IGNORED));
  return check_has_super(self, thd, var);
}
static Sys_var_bit Sys_log_update(
       "sql_log_update", "alias for sql_log_bin",
       SESSION_VAR(option_bits), NO_CMD_LINE, OPTION_BIN_LOG,
       DEFAULT(TRUE), NO_MUTEX_GUARD, NOT_IN_BINLOG,
       ON_CHECK(deprecated_log_update), ON_UPDATE(fix_sql_log_bin));

static Sys_var_bit Sys_sql_warnings(
       "sql_warnings", "sql_warnings",
       SESSION_VAR(option_bits), NO_CMD_LINE, OPTION_WARNINGS,
       DEFAULT(FALSE));

static Sys_var_bit Sys_sql_notes(
       "sql_notes", "sql_notes",
       SESSION_VAR(option_bits), NO_CMD_LINE, OPTION_SQL_NOTES,
       DEFAULT(TRUE));

static Sys_var_bit Sys_auto_is_null(
       "sql_auto_is_null", "sql_auto_is_null",
       SESSION_VAR(option_bits), NO_CMD_LINE, OPTION_AUTO_IS_NULL,
       DEFAULT(FALSE), NO_MUTEX_GUARD, IN_BINLOG);

static Sys_var_bit Sys_safe_updates(
       "sql_safe_updates", "sql_safe_updates",
       SESSION_VAR(option_bits), NO_CMD_LINE, OPTION_SAFE_UPDATES,
       DEFAULT(FALSE));

static Sys_var_bit Sys_buffer_results(
       "sql_buffer_result", "sql_buffer_result",
       SESSION_VAR(option_bits), NO_CMD_LINE, OPTION_BUFFER_RESULT,
       DEFAULT(FALSE));

static Sys_var_bit Sys_quote_show_create(
       "sql_quote_show_create", "sql_quote_show_create",
       SESSION_VAR(option_bits), NO_CMD_LINE, OPTION_QUOTE_SHOW_CREATE,
       DEFAULT(TRUE));

static Sys_var_bit Sys_foreign_key_checks(
       "foreign_key_checks", "foreign_key_checks",
       SESSION_VAR(option_bits), NO_CMD_LINE,
       REVERSE(OPTION_NO_FOREIGN_KEY_CHECKS),
       DEFAULT(TRUE), NO_MUTEX_GUARD, IN_BINLOG);

static Sys_var_bit Sys_unique_checks(
       "unique_checks", "unique_checks",
       SESSION_VAR(option_bits), NO_CMD_LINE,
       REVERSE(OPTION_RELAXED_UNIQUE_CHECKS),
       DEFAULT(TRUE), NO_MUTEX_GUARD, IN_BINLOG);

#ifdef ENABLED_PROFILING
static Sys_var_bit Sys_profiling(
       "profiling", "profiling",
       SESSION_VAR(option_bits), NO_CMD_LINE, OPTION_PROFILING,
       DEFAULT(FALSE));

static Sys_var_ulong Sys_profiling_history_size(
       "profiling_history_size", "Limit of query profiling memory",
       SESSION_VAR(profiling_history_size), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, 100), DEFAULT(15), BLOCK_SIZE(1));
#endif

static Sys_var_harows Sys_select_limit(
       "sql_select_limit",
       "The maximum number of rows to return from SELECT statements",
       SESSION_VAR(select_limit), NO_CMD_LINE,
       VALID_RANGE(1, HA_POS_ERROR), DEFAULT(HA_POS_ERROR), BLOCK_SIZE(1));

static bool update_timestamp(THD *thd, set_var *var)
{
  if (var->value)
    thd->set_time((time_t) var->save_result.ulonglong_value);
  else // SET timestamp=DEFAULT
    thd->user_time= 0;
  return false;
}
static ulonglong read_timestamp(THD *thd)
{
  return (ulonglong) thd->start_time;
}
static Sys_var_session_special Sys_timestamp(
       "timestamp", "Set the time for this client",
       sys_var::ONLY_SESSION, NO_CMD_LINE,
       VALID_RANGE(0, ~(time_t)0), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(0), ON_UPDATE(update_timestamp),
       ON_READ(read_timestamp));

static bool update_last_insert_id(THD *thd, set_var *var)
{
  if (!var->value)
  {
    my_error(ER_NO_DEFAULT, MYF(0), var->var->name);
    return true;
  }
  thd->first_successful_insert_id_in_prev_stmt=
    var->save_result.ulonglong_value;
  return false;
}
static ulonglong read_last_insert_id(THD *thd)
{
  return (ulonglong) thd->read_first_successful_insert_id_in_prev_stmt();
}
static Sys_var_session_special Sys_last_insert_id(
       "last_insert_id", "The value to be returned from LAST_INSERT_ID()",
       sys_var::ONLY_SESSION, NO_CMD_LINE,
       VALID_RANGE(0, ULONGLONG_MAX), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(update_last_insert_id), ON_READ(read_last_insert_id));

// alias for last_insert_id(), Sybase-style
static Sys_var_session_special Sys_identity(
       "identity", "Synonym for the last_insert_id variable",
       sys_var::ONLY_SESSION, NO_CMD_LINE,
       VALID_RANGE(0, ULONGLONG_MAX), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(update_last_insert_id), ON_READ(read_last_insert_id));

/*
  insert_id should *not* be marked as written to the binlog (i.e., it
  should *not* be IN_BINLOG), because we want any statement that
  refers to insert_id explicitly to be unsafe.  (By "explicitly", we
  mean using @@session.insert_id, whereas insert_id is used
  "implicitly" when NULL value is inserted into an auto_increment
  column).

  We want statements referring explicitly to @@session.insert_id to be
  unsafe, because insert_id is modified internally by the slave sql
  thread when NULL values are inserted in an AUTO_INCREMENT column.
  This modification interfers with the value of the
  @@session.insert_id variable if @@session.insert_id is referred
  explicitly by an insert statement (as is seen by executing "SET
  @@session.insert_id=0; CREATE TABLE t (a INT, b INT KEY
  AUTO_INCREMENT); INSERT INTO t(a) VALUES (@@session.insert_id);" in
  statement-based logging mode: t will be different on master and
  slave).
*/
static bool update_insert_id(THD *thd, set_var *var)
{
  if (!var->value)
  {
    my_error(ER_NO_DEFAULT, MYF(0), var->var->name);
    return true;
  }
  thd->force_one_auto_inc_interval(var->save_result.ulonglong_value);
  return false;
}

static ulonglong read_insert_id(THD *thd)
{
  return thd->auto_inc_intervals_forced.minimum();
}
static Sys_var_session_special Sys_insert_id(
       "insert_id", "The value to be used by the following INSERT "
       "or ALTER TABLE statement when inserting an AUTO_INCREMENT value",
       sys_var::ONLY_SESSION, NO_CMD_LINE,
       VALID_RANGE(0, ULONGLONG_MAX), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(update_insert_id), ON_READ(read_insert_id));

static bool update_rand_seed1(THD *thd, set_var *var)
{
  if (!var->value)
  {
    my_error(ER_NO_DEFAULT, MYF(0), var->var->name);
    return true;
  }
  thd->rand.seed1= (ulong) var->save_result.ulonglong_value;
  return false;
}
static ulonglong read_rand_seed(THD *thd)
{
  return 0;
}
static Sys_var_session_special Sys_rand_seed1(
       "rand_seed1", "Sets the internal state of the RAND() "
       "generator for replication purposes",
       sys_var::ONLY_SESSION, NO_CMD_LINE,
       VALID_RANGE(0, ULONG_MAX), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(update_rand_seed1), ON_READ(read_rand_seed));

static bool update_rand_seed2(THD *thd, set_var *var)
{
  if (!var->value)
  {
    my_error(ER_NO_DEFAULT, MYF(0), var->var->name);
    return true;
  }
  thd->rand.seed2= (ulong) var->save_result.ulonglong_value;
  return false;
}
static Sys_var_session_special Sys_rand_seed2(
       "rand_seed2", "Sets the internal state of the RAND() "
       "generator for replication purposes",
       sys_var::ONLY_SESSION, NO_CMD_LINE,
       VALID_RANGE(0, ULONG_MAX), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(update_rand_seed2), ON_READ(read_rand_seed));

static ulonglong read_error_count(THD *thd)
{
  return thd->warning_info->error_count();
}
// this really belongs to the SHOW STATUS
static Sys_var_session_special Sys_error_count(
       "error_count", "The number of errors that resulted from the "
       "last statement that generated messages",
       READ_ONLY sys_var::ONLY_SESSION, NO_CMD_LINE,
       VALID_RANGE(0, ULONGLONG_MAX), BLOCK_SIZE(1), NO_MUTEX_GUARD,
       NOT_IN_BINLOG, ON_CHECK(0), ON_UPDATE(0), ON_READ(read_error_count));

static ulonglong read_warning_count(THD *thd)
{
  return thd->warning_info->warn_count();
}
// this really belongs to the SHOW STATUS
static Sys_var_session_special Sys_warning_count(
       "warning_count", "The number of errors, warnings, and notes "
       "that resulted from the last statement that generated messages",
       READ_ONLY sys_var::ONLY_SESSION, NO_CMD_LINE,
       VALID_RANGE(0, ULONGLONG_MAX), BLOCK_SIZE(1), NO_MUTEX_GUARD,
       NOT_IN_BINLOG, ON_CHECK(0), ON_UPDATE(0), ON_READ(read_warning_count));

static Sys_var_ulong Sys_default_week_format(
       "default_week_format",
       "The default week format used by WEEK() functions",
       SESSION_VAR(default_week_format), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, 7), DEFAULT(0), BLOCK_SIZE(1));

static Sys_var_ulong Sys_group_concat_max_len(
       "group_concat_max_len",
       "The maximum length of the result of function  GROUP_CONCAT()",
       SESSION_VAR(group_concat_max_len), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(4, ULONG_MAX), DEFAULT(1024), BLOCK_SIZE(1));

static char *glob_hostname_ptr;
static Sys_var_charptr Sys_hostname(
       "hostname", "Server host name",
       READ_ONLY GLOBAL_VAR(glob_hostname_ptr), NO_CMD_LINE,
       IN_FS_CHARSET, DEFAULT(glob_hostname));

#ifndef EMBEDDED_LIBRARY
static Sys_var_charptr Sys_repl_report_host(
       "report_host",
       "Hostname or IP of the slave to be reported to the master during "
       "slave registration. Will appear in the output of SHOW SLAVE HOSTS. "
       "Leave unset if you do not want the slave to register itself with the "
       "master. Note that it is not sufficient for the master to simply read "
       "the IP of the slave off the socket once the slave connects. Due to "
       "NAT and other routing issues, that IP may not be valid for connecting "
       "to the slave from the master or other hosts",
       READ_ONLY GLOBAL_VAR(report_host), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_charptr Sys_repl_report_user(
       "report_user",
       "The account user name of the slave to be reported to the master "
       "during slave registration",
       READ_ONLY GLOBAL_VAR(report_user), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_charptr Sys_repl_report_password(
       "report_password",
       "The account password of the slave to be reported to the master "
       "during slave registration",
       READ_ONLY GLOBAL_VAR(report_password), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_uint Sys_repl_report_port(
       "report_port",
       "Port for connecting to slave reported to the master during slave "
       "registration. Set it only if the slave is listening on a non-default "
       "port or if you have a special tunnel from the master or other clients "
       "to the slave. If not sure, leave this option unset",
       READ_ONLY GLOBAL_VAR(report_port), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, UINT_MAX), DEFAULT(MYSQL_PORT), BLOCK_SIZE(1));
#endif

static Sys_var_mybool Sys_keep_files_on_create(
       "keep_files_on_create",
       "Don't overwrite stale .MYD and .MYI even if no directory is specified",
       SESSION_VAR(keep_files_on_create), CMD_LINE(OPT_ARG),
       DEFAULT(FALSE));

static char *license;
static Sys_var_charptr Sys_license(
       "license", "The type of license the server has",
       READ_ONLY GLOBAL_VAR(license), NO_CMD_LINE, IN_SYSTEM_CHARSET,
       DEFAULT(STRINGIFY_ARG(LICENSE)));

static bool check_log_path(sys_var *self, THD *thd, set_var *var)
{
  if (!var->value)
    return false; // DEFAULT is ok

  if (!var->save_result.string_value.str)
    return true;

  if (var->save_result.string_value.length > FN_REFLEN)
  { // path is too long
    my_error(ER_PATH_LENGTH, MYF(0), self->name.str);
    return true;
  }

  char path[FN_REFLEN];
  size_t path_length= unpack_filename(path, var->save_result.string_value.str);

  if (!path_length)
    return true;

  MY_STAT f_stat;

  if (my_stat(path, &f_stat, MYF(0)))
  {
    if (!MY_S_ISREG(f_stat.st_mode) || !(f_stat.st_mode & MY_S_IWRITE))
      return true; // not a regular writable file
    return false;
  }

  (void) dirname_part(path, var->save_result.string_value.str, &path_length);

  if (var->save_result.string_value.length - path_length >= FN_LEN)
  { // filename is too long
      my_error(ER_PATH_LENGTH, MYF(0), self->name.str);
      return true;
  }

  if (!path_length) // no path is good path (remember, relative to datadir)
    return false;

  if (my_access(path, (F_OK|W_OK)))
    return true; // directory is not writable

  return false;
}
static bool fix_log(char** logname, const char* default_logname,
                    const char*ext, bool enabled, void (*reopen)(char*))
{
  if (!*logname) // SET ... = DEFAULT
  {
    char buff[FN_REFLEN];
    *logname= my_strdup(make_log_name(buff, default_logname, ext),
                        MYF(MY_FAE+MY_WME));
    if (!*logname)
      return true;
  }
  logger.lock_exclusive();
  pthread_mutex_unlock(&LOCK_global_system_variables);
  if (enabled)
    reopen(*logname);
  logger.unlock();
  pthread_mutex_lock(&LOCK_global_system_variables);
  return false;
}
static void reopen_general_log(char* name)
{
  logger.get_log_file_handler()->close(0);
  logger.get_log_file_handler()->open_query_log(name);
}
static bool fix_general_log_file(sys_var *self, THD *thd, enum_var_type type)
{
  return fix_log(&opt_logname, default_logfile_name, ".log", opt_log,
                 reopen_general_log);
}
static Sys_var_charptr Sys_general_log_path(
       "general_log_file", "Log connections and queries to given file",
       PREALLOCATED GLOBAL_VAR(opt_logname), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0), NO_MUTEX_GUARD, NOT_IN_BINLOG,
       ON_CHECK(check_log_path), ON_UPDATE(fix_general_log_file));

static void reopen_slow_log(char* name)
{
  logger.get_slow_log_file_handler()->close(0);
  logger.get_slow_log_file_handler()->open_slow_log(name);
}
static bool fix_slow_log_file(sys_var *self, THD *thd, enum_var_type type)
{
  return fix_log(&opt_slow_logname, default_logfile_name, "-slow.log",
                 opt_slow_log, reopen_slow_log);
}
static Sys_var_charptr Sys_slow_log_path(
       "slow_query_log_file", "Log slow queries to given log file. "
       "Defaults logging to hostname-slow.log. Must be enabled to activate "
       "other slow log options",
       PREALLOCATED GLOBAL_VAR(opt_slow_logname), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0), NO_MUTEX_GUARD, NOT_IN_BINLOG,
       ON_CHECK(check_log_path), ON_UPDATE(fix_slow_log_file));

/// @todo deprecate these four legacy have_PLUGIN variables and use I_S instead
export SHOW_COMP_OPTION have_csv, have_innodb;
export SHOW_COMP_OPTION have_ndbcluster, have_partitioning;
static Sys_var_have Sys_have_csv(
       "have_csv", "have_csv",
       READ_ONLY GLOBAL_VAR(have_csv), NO_CMD_LINE);

static Sys_var_have Sys_have_innodb(
       "have_innodb", "have_innodb",
       READ_ONLY GLOBAL_VAR(have_innodb), NO_CMD_LINE);

static Sys_var_have Sys_have_ndbcluster(
       "have_ndbcluster", "have_ndbcluster",
       READ_ONLY GLOBAL_VAR(have_ndbcluster), NO_CMD_LINE);

static Sys_var_have Sys_have_partition_db(
       "have_partitioning", "have_partitioning",
       READ_ONLY GLOBAL_VAR(have_partitioning), NO_CMD_LINE);

static Sys_var_have Sys_have_compress(
       "have_compress", "have_compress",
       READ_ONLY GLOBAL_VAR(have_compress), NO_CMD_LINE);

static Sys_var_have Sys_have_crypt(
       "have_crypt", "have_crypt",
       READ_ONLY GLOBAL_VAR(have_crypt), NO_CMD_LINE);

static Sys_var_have Sys_have_dlopen(
       "have_dynamic_loading", "have_dynamic_loading",
       READ_ONLY GLOBAL_VAR(have_dlopen), NO_CMD_LINE);

static Sys_var_have Sys_have_geometry(
       "have_geometry", "have_geometry",
       READ_ONLY GLOBAL_VAR(have_geometry), NO_CMD_LINE);

static Sys_var_have Sys_have_openssl(
       "have_openssl", "have_openssl",
       READ_ONLY GLOBAL_VAR(have_ssl), NO_CMD_LINE);

static Sys_var_have Sys_have_profiling(
       "have_profiling", "have_profiling",
       READ_ONLY GLOBAL_VAR(have_profiling), NO_CMD_LINE);

static Sys_var_have Sys_have_query_cache(
       "have_query_cache", "have_query_cache",
       READ_ONLY GLOBAL_VAR(have_query_cache), NO_CMD_LINE);

static Sys_var_have Sys_have_rtree_keys(
       "have_rtree_keys", "have_rtree_keys",
       READ_ONLY GLOBAL_VAR(have_rtree_keys), NO_CMD_LINE);

static Sys_var_have Sys_have_ssl(
       "have_ssl", "have_ssl",
       READ_ONLY GLOBAL_VAR(have_ssl), NO_CMD_LINE);

static Sys_var_have Sys_have_symlink(
       "have_symlink", "have_symlink",
       READ_ONLY GLOBAL_VAR(have_symlink), NO_CMD_LINE);

static bool fix_log_state(sys_var *self, THD *thd, enum_var_type type);
static Sys_var_mybool Sys_general_log(
       "general_log", "Log connections and queries to a table or log file. "
       "Defaults logging to a file hostname.log or a table mysql.general_log"
       "if --log-output=TABLE is used",
       GLOBAL_VAR(opt_log), CMD_LINE(OPT_ARG),
       DEFAULT(FALSE), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_log_state));

// Synonym of "general_log" for consistency with SHOW VARIABLES output
static Sys_var_mybool Sys_log(
       "log", "Alias for --general-log. Deprecated",
       GLOBAL_VAR(opt_log), NO_CMD_LINE,
       DEFAULT(FALSE), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_log_state), DEPRECATED(70000, "'@@general_log'"));

static Sys_var_mybool Sys_slow_query_log(
       "slow_query_log",
       "Log slow queries to a table or log file. Defaults logging to a file "
       "hostname-slow.log or a table mysql.slow_log if --log-output=TABLE is "
       "used. Must be enabled to activate other slow log options",
       GLOBAL_VAR(opt_slow_log), CMD_LINE(OPT_ARG),
       DEFAULT(FALSE), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_log_state));

/* Synonym of "slow_query_log" for consistency with SHOW VARIABLES output */
static Sys_var_mybool Sys_log_slow(
       "log_slow_queries",
       "Alias for --slow-query-log. Deprecated",
       GLOBAL_VAR(opt_slow_log), NO_CMD_LINE,
       DEFAULT(FALSE), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_log_state), DEPRECATED(70000, "'@@slow_query_log'"));

static bool fix_log_state(sys_var *self, THD *thd, enum_var_type type)
{
  bool res;
  my_bool *newvalptr, newval, oldval;
  uint log_type;

  if (self == &Sys_general_log || self == &Sys_log)
  {
    newvalptr= &opt_log;
    oldval=    logger.get_log_file_handler()->is_open();
    log_type=  QUERY_LOG_GENERAL;
  }
  else if (self == &Sys_slow_query_log || self == &Sys_log_slow)
  {
    newvalptr= &opt_slow_log;
    oldval=    logger.get_slow_log_file_handler()->is_open();
    log_type=  QUERY_LOG_SLOW;
  }
  else
    DBUG_ASSERT(FALSE);

  newval= *newvalptr;
  if (oldval == newval)
    return false;

  *newvalptr= oldval; // [de]activate_log_handler works that way (sigh)

  pthread_mutex_unlock(&LOCK_global_system_variables);
  if (!newval)
  {
    logger.deactivate_log_handler(thd, log_type);
    res= false;
  }
  else
    res= logger.activate_log_handler(thd, log_type);
  pthread_mutex_lock(&LOCK_global_system_variables);
  return res;
}

static bool check_not_empty_set(sys_var *self, THD *thd, set_var *var)
{
  return var->save_result.ulonglong_value == 0;
}
static bool fix_log_output(sys_var *self, THD *thd, enum_var_type type)
{
  logger.lock_exclusive();
  logger.init_slow_log(log_output_options);
  logger.init_general_log(log_output_options);
  logger.unlock();
  return false;
}

static Sys_var_set Sys_log_output(
       "log_output", "Syntax: log-output=value[,value...], "
       "where \"value\" could be TABLE, FILE or NONE",
       GLOBAL_VAR(log_output_options), CMD_LINE(REQUIRED_ARG),
       log_output_names, DEFAULT(LOG_FILE), NO_MUTEX_GUARD, NOT_IN_BINLOG,
       ON_CHECK(check_not_empty_set), ON_UPDATE(fix_log_output));

#ifdef HAVE_REPLICATION
static Sys_var_mybool Sys_log_slave_updates(
       "log_slave_updates", "Tells the slave to log the updates from "
       "the slave thread to the binary log. You will need to turn it on if "
       "you plan to daisy-chain the slaves",
       READ_ONLY GLOBAL_VAR(opt_log_slave_updates), CMD_LINE(OPT_ARG),
       DEFAULT(0));

static Sys_var_charptr Sys_relay_log(
       "relay_log", "The location and name to use for relay logs",
       READ_ONLY GLOBAL_VAR(opt_relay_logname), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_charptr Sys_relay_log_index(
       "relay_log_index", "The location and name to use for the file "
       "that keeps a list of the last relay logs",
       READ_ONLY GLOBAL_VAR(opt_relaylog_index_name), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_charptr Sys_relay_log_info_file(
       "relay_log_info_file", "The location and name of the file that "
       "remembers where the SQL replication thread is in the relay logs",
       READ_ONLY GLOBAL_VAR(relay_log_info_file), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0));

static Sys_var_mybool Sys_relay_log_purge(
       "relay_log_purge", "if disabled - do not purge relay logs. "
       "if enabled - purge them as soon as they are no more needed",
       GLOBAL_VAR(relay_log_purge), CMD_LINE(OPT_ARG), DEFAULT(TRUE));

static Sys_var_mybool Sys_relay_log_recovery(
       "relay_log_recovery", "Enables automatic relay log recovery "
       "right after the database startup, which means that the IO Thread "
       "starts re-fetching from the master right after the last transaction "
       "processed",
       GLOBAL_VAR(relay_log_recovery), CMD_LINE(OPT_ARG), DEFAULT(FALSE));

static Sys_var_charptr Sys_slave_load_tmpdir(
       "slave_load_tmpdir", "The location where the slave should put "
       "its temporary files when replicating a LOAD DATA INFILE command",
       READ_ONLY GLOBAL_VAR(slave_load_tmpdir), CMD_LINE(REQUIRED_ARG),
       IN_FS_CHARSET, DEFAULT(0));

static bool fix_slave_net_timeout(sys_var *self, THD *thd, enum_var_type type)
{
  pthread_mutex_lock(&LOCK_active_mi);
  DBUG_PRINT("info", ("slave_net_timeout=%lu mi->heartbeat_period=%.3f",
                     slave_net_timeout,
                     (active_mi? active_mi->heartbeat_period : 0.0)));
  if (active_mi && slave_net_timeout < active_mi->heartbeat_period)
    push_warning_printf(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
                        ER_SLAVE_HEARTBEAT_VALUE_OUT_OF_RANGE,
                        "The current value for master_heartbeat_period"
                        " exceeds the new value of `slave_net_timeout' sec."
                        " A sensible value for the period should be"
                        " less than the timeout.");
  pthread_mutex_unlock(&LOCK_active_mi);
  return false;
}
static Sys_var_ulong Sys_slave_net_timeout(
       "slave_net_timeout", "Number of seconds to wait for more data "
       "from a master/slave connection before aborting the read",
       GLOBAL_VAR(slave_net_timeout), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(1, LONG_TIMEOUT), DEFAULT(SLAVE_NET_TIMEOUT), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
       ON_UPDATE(fix_slave_net_timeout));

static bool check_slave_skip_counter(sys_var *self, THD *thd, set_var *var)
{
  bool result= false;
  pthread_mutex_lock(&LOCK_active_mi);
  pthread_mutex_lock(&active_mi->rli.run_lock);
  if (active_mi->rli.slave_running)
  {
    my_message(ER_SLAVE_MUST_STOP, ER(ER_SLAVE_MUST_STOP), MYF(0));
    result= true;
  }
  pthread_mutex_unlock(&active_mi->rli.run_lock);
  pthread_mutex_unlock(&LOCK_active_mi);
  return result;
}
static bool fix_slave_skip_counter(sys_var *self, THD *thd, enum_var_type type)
{
  pthread_mutex_lock(&LOCK_active_mi);
  pthread_mutex_lock(&active_mi->rli.run_lock);
  /*
    The following test should normally never be true as we test this
    in the check function;  To be safe against multiple
    SQL_SLAVE_SKIP_COUNTER request, we do the check anyway
  */
  if (!active_mi->rli.slave_running)
  {
    pthread_mutex_lock(&active_mi->rli.data_lock);
    active_mi->rli.slave_skip_counter= sql_slave_skip_counter;
    pthread_mutex_unlock(&active_mi->rli.data_lock);
  }
  pthread_mutex_unlock(&active_mi->rli.run_lock);
  pthread_mutex_unlock(&LOCK_active_mi);
  return 0;
}
static Sys_var_uint Sys_slave_skip_counter(
       "sql_slave_skip_counter", "sql_slave_skip_counter",
       GLOBAL_VAR(sql_slave_skip_counter), NO_CMD_LINE,
       VALID_RANGE(0, UINT_MAX), DEFAULT(0), BLOCK_SIZE(1),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(check_slave_skip_counter),
       ON_UPDATE(fix_slave_skip_counter));

static Sys_var_charptr Sys_slave_skip_errors(
       "slave_skip_errors", "Tells the slave thread to continue "
       "replication when a query event returns an error from the "
       "provided list",
       READ_ONLY GLOBAL_VAR(opt_slave_skip_errors), CMD_LINE(REQUIRED_ARG),
       IN_SYSTEM_CHARSET, DEFAULT(0));

static Sys_var_ulonglong Sys_relay_log_space_limit(
       "relay_log_space_limit", "Maximum space to use for all relay logs",
       READ_ONLY GLOBAL_VAR(relay_log_space_limit), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, ULONG_MAX), DEFAULT(0), BLOCK_SIZE(1));

static Sys_var_uint Sys_sync_relaylog_period(
       "sync_relay_log", "Synchronously flush relay log to disk after "
       "every #th event. Use 0 (default) to disable synchronous flushing",
       GLOBAL_VAR(sync_relaylog_period), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, UINT_MAX), DEFAULT(0), BLOCK_SIZE(1));

static Sys_var_uint Sys_sync_relayloginfo_period(
       "sync_relay_log_info", "Synchronously flush relay log info "
       "to disk after every #th transaction. Use 0 (default) to disable "
       "synchronous flushing",
       GLOBAL_VAR(sync_relayloginfo_period), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, UINT_MAX), DEFAULT(0), BLOCK_SIZE(1));
#endif

static Sys_var_uint Sys_sync_binlog_period(
       "sync_binlog", "Synchronously flush binary log to disk after "
       "every #th event. Use 0 (default) to disable synchronous flushing",
       GLOBAL_VAR(sync_binlog_period), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, UINT_MAX), DEFAULT(0), BLOCK_SIZE(1));

static Sys_var_uint Sys_sync_masterinfo_period(
       "sync_master_info", "Synchronously flush master info to disk "
       "after every #th event. Use 0 (default) to disable synchronous flushing",
       GLOBAL_VAR(sync_masterinfo_period), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, UINT_MAX), DEFAULT(0), BLOCK_SIZE(1));

#ifdef HAVE_REPLICATION
static Sys_var_ulong Sys_slave_trans_retries(
       "slave_transaction_retries", "Number of times the slave SQL "
       "thread will retry a transaction in case it failed with a deadlock "
       "or elapsed lock wait timeout, before giving up and stopping",
       GLOBAL_VAR(slave_trans_retries), CMD_LINE(REQUIRED_ARG),
       VALID_RANGE(0, ULONG_MAX), DEFAULT(10), BLOCK_SIZE(1));
#endif

static bool check_locale(sys_var *self, THD *thd, set_var *var)
{
  if (!var->value)
    return false;

  MY_LOCALE *locale;
  char buff[STRING_BUFFER_USUAL_SIZE];
  if (var->value->result_type() == INT_RESULT)
  {
    int lcno= (int)var->value->val_int();
    if (!(locale= my_locale_by_number(lcno)))
    {
      my_error(ER_UNKNOWN_LOCALE, MYF(0), llstr(lcno, buff));
      return true;
    }
    if (check_not_null(self, thd, var))
      return true;
  }
  else // STRING_RESULT
  {
    String str(buff, sizeof(buff), system_charset_info), *res;
    if (!(res=var->value->val_str(&str)))
      return true;
    else if (!(locale= my_locale_by_name(res->c_ptr())))
    {
      ErrConvString err(res);
      my_error(ER_UNKNOWN_LOCALE, MYF(0), err.ptr());
      return true;
    }
  }

  var->save_result.ptr= locale;

  if (!locale->errmsgs->errmsgs)
  {
    pthread_mutex_lock(&LOCK_error_messages);
    if (!locale->errmsgs->errmsgs &&
        read_texts(ERRMSG_FILE, locale->errmsgs->language,
                   &locale->errmsgs->errmsgs,
                   ER_ERROR_LAST - ER_ERROR_FIRST + 1))
    {
      push_warning_printf(thd, MYSQL_ERROR::WARN_LEVEL_WARN, ER_UNKNOWN_ERROR,
                          "Can't process error message file for locale '%s'",
                          locale->name);
      pthread_mutex_unlock(&LOCK_error_messages);
      return true;
    }
    pthread_mutex_unlock(&LOCK_error_messages);
  }
  return false;
}
static Sys_var_struct Sys_lc_messages(
       "lc_messages", "Set the language used for the error messages",
       SESSION_VAR(lc_messages), NO_CMD_LINE,
       offsetof(MY_LOCALE, name), DEFAULT(&my_default_lc_messages),
       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(check_locale));

static Sys_var_struct Sys_lc_time_names(
       "lc_time_names", "Set the language used for the month "
       "names and the days of the week",
       SESSION_VAR(lc_time_names), NO_CMD_LINE,
       offsetof(MY_LOCALE, name), DEFAULT(&my_default_lc_time_names),
       NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(check_locale));

static Sys_var_tz Sys_time_zone(
       "time_zone", "time_zone",
       SESSION_VAR(time_zone), NO_CMD_LINE,
       DEFAULT(&default_tz), NO_MUTEX_GUARD, IN_BINLOG);