Bug#13233

  select distinct char(column) fails with utf8
ctype_utf8.result, ctype_utf8.test:
  Adding test case
sql_yacc.yy:
  Adding new syntax.
item_strfunc.h:
  Fixing wrong max_length calculation.
  Also, adding CHAR(x USING charset),
  for easier migrating from 4.1 to 5.0,
  according to Monty's suggestion.

mysql-test/r/ctype_utf8.result

@@ -1061,3 +1061,12 @@ create table t1 (a varchar(255)) default charset=utf8;
 select * from t1 where find_in_set('-1', a);
 a
 drop table t1;
+create table t1 (a int);
+insert into t1 values (48),(49),(50);
+set names utf8;
+select distinct char(a) from t1;
+char(a)
+0
+1
+2
+drop table t1;

mysql-test/t/ctype_utf8.test

@@ -873,4 +873,13 @@ create table t1 (a varchar(255)) default charset=utf8;
 select * from t1 where find_in_set('-1', a);
 drop table t1;
 
+#
+# Bug#13233: select distinct char(column) fails with utf8
+#
+create table t1 (a int);
+insert into t1 values (48),(49),(50);
+set names utf8;
+select distinct char(a) from t1;
+drop table t1;
+
 # End of 4.1 tests

sql/item_strfunc.h

@@ -444,12 +444,15 @@ public:
 class Item_func_char :public Item_str_func
 {
 public:
-  Item_func_char(List<Item> &list) :Item_str_func(list) {}
+  Item_func_char(List<Item> &list) :Item_str_func(list)
+  { collation.set(default_charset()); }
+  Item_func_char(List<Item> &list, CHARSET_INFO *cs) :Item_str_func(list)
+  { collation.set(cs); }
   String *val_str(String *);
   void fix_length_and_dec() 
   { 
-    collation.set(default_charset());
-    maybe_null=0; max_length=arg_count;
+    maybe_null=0;
+    max_length=arg_count * collation.collation->mbmaxlen;
   }
   const char *func_name() const { return "char"; }
 };

sql/sql_yacc.yy

@@ -2924,6 +2924,8 @@ simple_expr:
 	  { $$= new Item_func_atan($3,$5); }
 	| CHAR_SYM '(' expr_list ')'
 	  { $$= new Item_func_char(*$3); }
+	| CHAR_SYM '(' expr_list USING charset_name ')'
+	  { $$= new Item_func_char(*$3, $5); }
 	| CHARSET '(' expr ')'
 	  { $$= new Item_func_charset($3); }
 	| COALESCE '(' expr_list ')'