Bug #6658 MAX(column) returns incorrect coercibility

Also, Item_sum_hybrid->charset was removed as redundant,
and switched to use collation.collation instead.

mysql-test/r/func_group.result

@@ -637,8 +637,22 @@ create table t1 (a char(10));
 insert into t1 values ('a'),('b'),('c');
 select coercibility(max(a)) from t1;
 coercibility(max(a))
-3
+2
 drop table t1;
+create table t1 (a char character set latin2);
+insert into t1 values ('a'),('b');
+select charset(max(a)), coercibility(max(a)),
+charset(min(a)), coercibility(min(a)) from t1;
+charset(max(a))	coercibility(max(a))	charset(min(a))	coercibility(min(a))
+latin2	2	latin2	2
+create table t2 select max(a),min(a) from t1;
+show create table t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `max(a)` char(1) character set latin2 default NULL,
+  `min(a)` char(1) character set latin2 default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t2,t1;
 create table t1 (a int);
 insert into t1 values (1);
 select max(a) as b from t1 having b=1;

mysql-test/r/func_str.result

@@ -614,6 +614,20 @@ t1	CREATE TABLE `t1` (
   `encode('abcd','ab')` binary(4) NOT NULL default ''
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
+create table t1 (a char character set latin2);
+insert into t1 values ('a'),('b');
+select charset(max(a)), coercibility(max(a)),
+charset(min(a)), coercibility(min(a)) from t1;
+charset(max(a))	coercibility(max(a))	charset(min(a))	coercibility(min(a))
+latin2	2	latin2	2
+create table t2 select max(a),min(a) from t1;
+show create table t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `max(a)` char(1) character set latin2 default NULL,
+  `min(a)` char(1) character set latin2 default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t2,t1;
 select SUBSTR('abcdefg',3,2);
 SUBSTR('abcdefg',3,2)
 cd

mysql-test/t/func_group.test

@@ -383,6 +383,17 @@ insert into t1 values ('a'),('b'),('c');
 select coercibility(max(a)) from t1;
 drop table t1;
 
+#
+# Bug #6658 MAX(column) returns incorrect coercibility
+#
+create table t1 (a char character set latin2);
+insert into t1 values ('a'),('b');
+select charset(max(a)), coercibility(max(a)),
+       charset(min(a)), coercibility(min(a)) from t1;
+create table t2 select max(a),min(a) from t1;
+show create table t2;
+drop table t2,t1;
+
 #
 # aggregate functions on static tables
 #

sql/item_func.cc

@@ -350,6 +350,7 @@ void Item_func::split_sum_func(THD *thd, Item **ref_pointer_array,
     {
       uint el= fields.elements;
       Item *new_item= new Item_ref(ref_pointer_array + el, 0, item->name);
+      new_item->collation.set(item->collation);
       fields.push_front(item);
       ref_pointer_array[el]= item;
       thd->change_item_tree(arg, new_item);

sql/item_sum.cc

@@ -218,16 +218,13 @@ Item_sum_hybrid::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
   hybrid_type= item->result_type();
   if (hybrid_type == INT_RESULT)
   {
-    cmp_charset= &my_charset_bin;
     max_length=20;
   }
   else if (hybrid_type == REAL_RESULT)
   {
-    cmp_charset= &my_charset_bin;
     max_length=float_length(decimals);
   }else
   {
-    cmp_charset= item->collation.collation;
     max_length=item->max_length;
   }
   decimals=item->decimals;
@@ -557,7 +554,7 @@ bool Item_sum_min::add()
   {
     String *result=args[0]->val_str(&tmp_value);
     if (!args[0]->null_value &&
-	(null_value || sortcmp(&value,result,cmp_charset) > 0))
+	(null_value || sortcmp(&value,result,collation.collation) > 0))
     {
       value.copy(*result);
       null_value=0;
@@ -610,7 +607,7 @@ bool Item_sum_max::add()
   {
     String *result=args[0]->val_str(&tmp_value);
     if (!args[0]->null_value &&
-	(null_value || sortcmp(&value,result,cmp_charset) < 0))
+	(null_value || sortcmp(&value,result,collation.collation) < 0))
     {
       value.copy(*result);
       null_value=0;
@@ -921,7 +918,7 @@ Item_sum_hybrid::min_max_update_str_field()
     result_field->val_str(&tmp_value);
 
     if (result_field->is_null() ||
-	(cmp_sign * sortcmp(res_str,&tmp_value,cmp_charset)) < 0)
+	(cmp_sign * sortcmp(res_str,&tmp_value,collation.collation)) < 0)
       result_field->store(res_str->ptr(),res_str->length(),res_str->charset());
     result_field->set_notnull();
   }

sql/item_sum.h

@@ -402,20 +402,19 @@ class Item_sum_hybrid :public Item_sum
   enum_field_types hybrid_field_type;
   int cmp_sign;
   table_map used_table_cache;
-  CHARSET_INFO *cmp_charset;
 
   public:
   Item_sum_hybrid(Item *item_par,int sign)
     :Item_sum(item_par), sum(0.0), sum_int(0),
     hybrid_type(INT_RESULT), hybrid_field_type(FIELD_TYPE_LONGLONG),
-    cmp_sign(sign), used_table_cache(~(table_map) 0),
-    cmp_charset(&my_charset_bin)
-  {}
+    cmp_sign(sign), used_table_cache(~(table_map) 0)
+  { collation.set(&my_charset_bin); }
   Item_sum_hybrid(THD *thd, Item_sum_hybrid *item):
     Item_sum(thd, item), value(item->value),
     sum(item->sum), sum_int(item->sum_int), hybrid_type(item->hybrid_type),
     hybrid_field_type(item->hybrid_field_type),cmp_sign(item->cmp_sign), 
-    used_table_cache(item->used_table_cache), cmp_charset(item->cmp_charset) {}
+    used_table_cache(item->used_table_cache)
+    { collation.set(item->collation); }
   bool fix_fields(THD *, TABLE_LIST *, Item **);
   table_map used_tables() const { return used_table_cache; }
   bool const_item() const { return !used_table_cache; }