Don't force column header to @@session.var_name if @@local.var_name

was used. (Bug #10724)

mysql-test/r/key_cache.result

@@ -23,13 +23,13 @@ SELECT @@global.default.key_buffer_size;
 @@global.default.key_buffer_size
 16777216
 SELECT @@global.default.`key_buffer_size`;
-@@global.default.key_buffer_size
+@@global.default.`key_buffer_size`
 16777216
 SELECT @@global.`default`.`key_buffer_size`;
-@@global.default.key_buffer_size
+@@global.`default`.`key_buffer_size`
 16777216
 SELECT @@`default`.key_buffer_size;
-@@default.key_buffer_size
+@@`default`.key_buffer_size
 16777216
 SELECT @@small.key_buffer_size;
 @@small.key_buffer_size

mysql-test/r/ps_1general.result

@@ -332,7 +332,7 @@ execute stmt1 ;
 ERROR 42S02: Unknown table 't5'
 prepare stmt1 from ' SELECT @@version ' ;
 execute stmt1 ;
-@@VERSION
+@@version
 <version>
 prepare stmt_do from ' do @var:=  (1 in (select a from t1)) ' ;
 prepare stmt_set from ' set @var= (1 in (select a from t1)) ' ;

mysql-test/r/user_var.result

@@ -179,3 +179,27 @@ set session @honk=99;
 ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '@honk=99' at line 1
 set one_shot @honk=99;
 ERROR HY000: The SET ONE_SHOT syntax is reserved for purposes internal to the MySQL server
+select @@local.max_allowed_packet;
+@@local.max_allowed_packet
+#
+select @@session.max_allowed_packet;
+@@session.max_allowed_packet
+#
+select @@global.max_allowed_packet;
+@@global.max_allowed_packet
+#
+select @@max_allowed_packet;
+@@max_allowed_packet
+#
+select @@Max_Allowed_Packet;
+@@Max_Allowed_Packet
+#
+select @@version;
+@@version
+#
+select @@global.version;
+@@global.version
+#
+select @@session.VERSION;
+@@session.VERSION
+#

mysql-test/r/variables.result

@@ -70,7 +70,7 @@ Variable_name	Value
 max_join_size	HA_POS_ERROR
 set @@max_join_size=1000, @@global.max_join_size=2000;
 select @@local.max_join_size, @@global.max_join_size;
-@@session.max_join_size	@@global.max_join_size
+@@local.max_join_size	@@global.max_join_size
 1000	2000
 select @@identity,  length(@@version)>0;
 @@identity	length(@@version)>0
@@ -407,23 +407,23 @@ Variable_name	Value
 myisam_max_sort_file_size	MAX_FILE_SIZE
 set global myisam_max_sort_file_size=default;
 select @@global.max_user_connections,@@local.max_join_size;
-@@global.max_user_connections	@@session.max_join_size
+@@global.max_user_connections	@@local.max_join_size
 100	200
 set @svc=@@global.max_user_connections, @svj=@@local.max_join_size;
 select @@global.max_user_connections,@@local.max_join_size;
-@@global.max_user_connections	@@session.max_join_size
+@@global.max_user_connections	@@local.max_join_size
 100	200
 set @@global.max_user_connections=111,@@local.max_join_size=222;
 select @@global.max_user_connections,@@local.max_join_size;
-@@global.max_user_connections	@@session.max_join_size
+@@global.max_user_connections	@@local.max_join_size
 111	222
 set @@global.max_user_connections=@@local.max_join_size,@@local.max_join_size=@@global.max_user_connections;
 select @@global.max_user_connections,@@local.max_join_size;
-@@global.max_user_connections	@@session.max_join_size
+@@global.max_user_connections	@@local.max_join_size
 222	111
 set @@global.max_user_connections=@svc, @@local.max_join_size=@svj;
 select @@global.max_user_connections,@@local.max_join_size;
-@@global.max_user_connections	@@session.max_join_size
+@@global.max_user_connections	@@local.max_join_size
 100	200
 set @a=1, @b=2;
 set @a=@b, @b=@a;

mysql-test/t/user_var.test

@@ -119,3 +119,24 @@ select coercibility(@v1),coercibility(@v2),coercibility(@v3),coercibility(@v4);
 set session @honk=99;
 --error 1105
 set one_shot @honk=99;
+
+#
+# Bug #10724  @@local not preserved in column name of select
+#
+# The value doesn't actually matter, we just care about the column name
+--replace_column 1 #
+select @@local.max_allowed_packet;
+--replace_column 1 #
+select @@session.max_allowed_packet;
+--replace_column 1 #
+select @@global.max_allowed_packet;
+--replace_column 1 #
+select @@max_allowed_packet;
+--replace_column 1 #
+select @@Max_Allowed_Packet;
+--replace_column 1 #
+select @@version;
+--replace_column 1 #
+select @@global.version;
+--replace_column 1 #
+select @@session.VERSION;

sql/item_func.cc

@@ -3417,7 +3417,7 @@ Item *get_system_var(THD *thd, enum_var_type var_type, LEX_STRING name,
 
   if (component.str == 0 &&
       !my_strcasecmp(system_charset_info, name.str, "VERSION"))
-    return new Item_string("@@VERSION", server_version,
+    return new Item_string(NULL, server_version,
 			   (uint) strlen(server_version),
 			   system_charset_info, DERIVATION_SYSCONST);
 
@@ -3444,28 +3444,10 @@ Item *get_system_var(THD *thd, enum_var_type var_type, LEX_STRING name,
   }
   thd->lex->uncacheable(UNCACHEABLE_SIDEEFFECT);
 
-  buff[0]='@';
-  buff[1]='@';
-  pos=buff+2;
-  if (var_type == OPT_SESSION)
-    pos=strmov(pos,"session.");
-  else if (var_type == OPT_GLOBAL)
-    pos=strmov(pos,"global.");
-  
   set_if_smaller(component_name->length, MAX_SYS_VAR_LENGTH);
-  set_if_smaller(base_name->length, MAX_SYS_VAR_LENGTH);
-
-  if (component_name->str)
-  {
-    memcpy(pos, component_name->str, component_name->length);
-    pos+= component_name->length;
-    *pos++= '.';
-  }
-  memcpy(pos, base_name->str, base_name->length);
-  pos+= base_name->length;
 
   return new Item_func_get_system_var(var, var_type, component_name,
-                                      buff, pos - buff);
+                                      NULL, 0);
 }
 
 

sql/sql_parse.cc

@@ -4197,6 +4197,8 @@ void create_select_for_variable(const char *var_name)
   THD *thd;
   LEX *lex;
   LEX_STRING tmp, null_lex_string;
+  Item *var;
+  char buff[MAX_SYS_VAR_LENGTH*2+4+8], *end;
   DBUG_ENTER("create_select_for_variable");
 
   thd= current_thd;
@@ -4206,8 +4208,14 @@ void create_select_for_variable(const char *var_name)
   tmp.str= (char*) var_name;
   tmp.length=strlen(var_name);
   bzero((char*) &null_lex_string.str, sizeof(null_lex_string));
-  add_item_to_list(thd, get_system_var(thd, OPT_SESSION, tmp,
-				       null_lex_string));
+  /*
+    We set the name of Item to @@session.var_name because that then is used
+    as the column name in the output.
+  */
+  var= get_system_var(thd, OPT_SESSION, tmp, null_lex_string);
+  end= strxmov(buff, "@@session.", var_name, NullS);
+  var->set_name(buff, end-buff, system_charset_info);
+  add_item_to_list(thd, var);
   DBUG_VOID_RETURN;
 }