Fix for bug #22026: Warning when using IF statement and large unsigned bigint

  
We use INT_RESULT type if all arguments are of type INT for 'if', 'case', 
'coalesce' functions regardless of arguments' unsigned flag, so sometimes we can
exceed the INT bounds.

mysql-test/r/select.result

@@ -3634,3 +3634,33 @@ INSERT into t1 values (1), (2), (3);
 SELECT * FROM t1 LIMIT 2, -1;
 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 '-1' at line 1
 DROP TABLE t1;
+create table t1 (a bigint unsigned);
+insert into t1 values
+(if(1, 9223372036854775808, 1)),
+(case when 1 then 9223372036854775808 else 1 end),
+(coalesce(9223372036854775808, 1));
+select * from t1;
+a
+9223372036854775808
+9223372036854775808
+9223372036854775808
+drop table t1;
+create table t1 select
+if(1, 9223372036854775808, 1) i,
+case when 1 then 9223372036854775808 else 1 end c,
+coalesce(9223372036854775808, 1) co;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `i` decimal(19,0) NOT NULL default '0',
+  `c` decimal(19,0) NOT NULL default '0',
+  `co` decimal(19,0) NOT NULL default '0'
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;
+select 
+if(1, cast(1111111111111111111 as unsigned), 1) i,
+case when 1 then cast(1111111111111111111 as unsigned) else 1 end c,
+coalesce(cast(1111111111111111111 as unsigned), 1) co;
+i	c	co
+1111111111111111111	1111111111111111111	1111111111111111111
+End of 5.0 tests

mysql-test/t/select.test

@@ -3123,3 +3123,27 @@ SELECT * FROM t1 LIMIT 2, -1;
 
 DROP TABLE t1;
 
+#
+# Bug #22026: Warning when using IF statement and large unsigned bigint
+#
+
+create table t1 (a bigint unsigned);
+insert into t1 values
+  (if(1, 9223372036854775808, 1)),
+  (case when 1 then 9223372036854775808 else 1 end),
+  (coalesce(9223372036854775808, 1));
+select * from t1;
+drop table t1;
+create table t1 select
+  if(1, 9223372036854775808, 1) i,
+  case when 1 then 9223372036854775808 else 1 end c,
+  coalesce(9223372036854775808, 1) co;
+show create table t1;
+drop table t1;
+# Ensure we handle big values properly
+select 
+  if(1, cast(1111111111111111111 as unsigned), 1) i,
+  case when 1 then cast(1111111111111111111 as unsigned) else 1 end c,
+  coalesce(cast(1111111111111111111 as unsigned), 1) co;
+
+--echo End of 5.0 tests

sql/item_cmpfunc.cc

@@ -26,13 +26,17 @@
 
 static bool convert_constant_item(THD *thd, Field *field, Item **item);
 
-static Item_result item_store_type(Item_result a,Item_result b)
+static Item_result item_store_type(Item_result a, Item *item,
+                                   my_bool unsigned_flag)
 {
+  Item_result b= item->result_type();
+
   if (a == STRING_RESULT || b == STRING_RESULT)
     return STRING_RESULT;
   else if (a == REAL_RESULT || b == REAL_RESULT)
     return REAL_RESULT;
-  else if (a == DECIMAL_RESULT || b == DECIMAL_RESULT)
+  else if (a == DECIMAL_RESULT || b == DECIMAL_RESULT ||
+           unsigned_flag != item->unsigned_flag)
     return DECIMAL_RESULT;
   else
     return INT_RESULT;
@@ -41,6 +45,7 @@ static Item_result item_store_type(Item_result a,Item_result b)
 static void agg_result_type(Item_result *type, Item **items, uint nitems)
 {
   Item **item, **item_end;
+  my_bool unsigned_flag= 0;
 
   *type= STRING_RESULT;
   /* Skip beginning NULL items */
@@ -49,6 +54,7 @@ static void agg_result_type(Item_result *type, Item **items, uint nitems)
     if ((*item)->type() != Item::NULL_ITEM)
     {
       *type= (*item)->result_type();
+      unsigned_flag= (*item)->unsigned_flag;
       item++;
       break;
     }
@@ -57,7 +63,7 @@ static void agg_result_type(Item_result *type, Item **items, uint nitems)
   for (; item < item_end; item++)
   {
     if ((*item)->type() != Item::NULL_ITEM)
-      *type= item_store_type(type[0], (*item)->result_type());
+      *type= item_store_type(*type, *item, unsigned_flag);
   }
 }