Optimize charset tracking a bit.

sql/set_var.cc

@@ -1016,24 +1016,12 @@ int set_var_collation_client::update(THD *thd)
 #ifndef EMBEDDED_LIBRARY
   if (thd->session_tracker.get_tracker(SESSION_SYSVARS_TRACKER)->is_enabled())
   {
-    sys_var *svar;
-    mysql_mutex_lock(&LOCK_plugin);
-    if ((svar= find_sys_var_ex(thd, "character_set_client",
-                               sizeof("character_set_client") - 1,
-                               false, true)))
     thd->session_tracker.get_tracker(SESSION_SYSVARS_TRACKER)->
-        mark_as_changed(thd, (LEX_CSTRING*)svar);
-    if ((svar= find_sys_var_ex(thd, "character_set_results",
-                             sizeof("character_set_results") - 1,
-                               false, true)))
+      mark_as_changed(thd, (LEX_CSTRING*)Sys_character_set_client_ptr);
     thd->session_tracker.get_tracker(SESSION_SYSVARS_TRACKER)->
-        mark_as_changed(thd, (LEX_CSTRING*)svar);
-    if ((svar= find_sys_var_ex(thd, "character_set_connection",
-                                sizeof("character_set_connection") - 1,
-                               false, true)))
+      mark_as_changed(thd, (LEX_CSTRING*)Sys_character_set_results_ptr);
     thd->session_tracker.get_tracker(SESSION_SYSVARS_TRACKER)->
-        mark_as_changed(thd, (LEX_CSTRING*)svar);
-    mysql_mutex_unlock(&LOCK_plugin);
+      mark_as_changed(thd, (LEX_CSTRING*)Sys_character_set_connection_ptr);
   }
   thd->session_tracker.mark_as_changed(thd, SESSION_STATE_CHANGE_TRACKER, NULL);
 #endif //EMBEDDED_LIBRARY

sql/set_var.h

@@ -430,7 +430,9 @@ sql_mode_t expand_sql_mode(sql_mode_t sql_mode);
 bool sql_mode_string_representation(THD *thd, sql_mode_t sql_mode, LEX_STRING *ls);
 int default_regex_flags_pcre(const THD *thd);
 
-extern sys_var *Sys_autocommit_ptr, *Sys_last_gtid_ptr;
+extern sys_var *Sys_autocommit_ptr, *Sys_last_gtid_ptr,
+  *Sys_character_set_client_ptr, *Sys_character_set_connection_ptr,
+  *Sys_character_set_results_ptr;
 
 CHARSET_INFO *get_old_charset_by_name(const char *old_name);
 

sql/sys_vars.cc

@@ -673,6 +673,8 @@ static Sys_var_struct Sys_character_set_client(
        offsetof(CHARSET_INFO, csname), DEFAULT(&default_charset_info),
        NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(check_cs_client),
        ON_UPDATE(fix_thd_charset));
+// for check changing
+export sys_var *Sys_character_set_client_ptr= &Sys_character_set_client;
 
 static Sys_var_struct Sys_character_set_connection(
        "character_set_connection", "The character set used for "
@@ -682,6 +684,8 @@ static Sys_var_struct Sys_character_set_connection(
        offsetof(CHARSET_INFO, csname), DEFAULT(&default_charset_info),
        NO_MUTEX_GUARD, IN_BINLOG, ON_CHECK(check_charset_not_null),
        ON_UPDATE(fix_thd_charset));
+// for check changing
+export sys_var *Sys_character_set_connection_ptr= &Sys_character_set_connection;
 
 static Sys_var_struct Sys_character_set_results(
        "character_set_results", "The character set used for returning "
@@ -689,6 +693,8 @@ static Sys_var_struct Sys_character_set_results(
        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));
+// for check changing
+export sys_var *Sys_character_set_results_ptr= &Sys_character_set_results;
 
 static Sys_var_struct Sys_character_set_filesystem(
        "character_set_filesystem", "The filesystem character set",