Bug #12829

Cannot convert the charset of a GROUP_CONCAT result:

item_sum.cc:
  "result" character set was not set into proper value.

func_gconcat.result, func_gconcat.test:
  Fixing tests accordingly.

mysql-test/r/func_gconcat.result

@@ -469,6 +469,15 @@ select collation(group_concat(a,b)) from t1;
 ERROR HY000: Illegal mix of collations (cp1250_general_ci,IMPLICIT) and (koi8r_general_ci,IMPLICIT) for operation 'group_concat'
 drop table t1;
 drop table t2;
+CREATE TABLE t1 (a CHAR(10) CHARACTER SET cp850);
+INSERT INTO t1 VALUES ('');
+SELECT a FROM t1;
+a
+
+SELECT GROUP_CONCAT(a) FROM t1;
+GROUP_CONCAT(a)
+
+DROP TABLE t1;
 CREATE TABLE t1 (id int);
 SELECT GROUP_CONCAT(id) AS gc FROM t1 HAVING gc IS NULL;
 gc

mysql-test/t/func_gconcat.test

@@ -281,6 +281,16 @@ select collation(group_concat(a,b)) from t1;
 drop table t1;
 drop table t2;
 
+#
+# Bug #12829
+# Cannot convert the charset of a GROUP_CONCAT result
+#
+CREATE TABLE t1 (a CHAR(10) CHARACTER SET cp850);
+INSERT INTO t1 VALUES ('');
+SELECT a FROM t1;
+SELECT GROUP_CONCAT(a) FROM t1;
+DROP TABLE t1;
+
 #
 # bug #7769: group_concat returning null is checked in having
 #

sql/item_sum.cc

@@ -1937,6 +1937,7 @@ Item_func_group_concat::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
                         args, arg_count, MY_COLL_ALLOW_CONV))
     return 1;
 
+  result.set_charset(collation.collation);
   result_field= 0;
   null_value= 1;
   max_length= group_concat_max_len;