Bug #11766094 - 59132: MIN() AND MAX() REMOVE UNSIGNEDNESS

In the string context the MIN() and MAX() functions don't take
into account the unsignedness of the UNSIGNED BIGINT argument
column.

I.e.:
        CREATE TABLE t1 (a BIGINT UNSIGNED);
        INSERT INTO t1 VALUES (18446668621106209655);
        SELECT CONCAT(MAX(a)) FROM t1;

returns -75452603341961.

mysql-test/r/func_group.result

@@ -1737,4 +1737,13 @@ SELECT MIN(GET_LOCK('aaaaaaaaaaaaaaaaa',0) / '0b11111111111111111111111111111111
 SELECT MIN(GET_LOCK('aaaaaaaaaaaaaaaaa',0) / '0b1111111111111111111111111111111111111111111111111111111111111111111111111' ^ (RAND()));
 SELECT RELEASE_LOCK('aaaaaaaaaaaaaaaaa');
 #
+# Bug #11766094 - 59132: MIN() AND MAX() REMOVE UNSIGNEDNESS 
+#
+CREATE TABLE t1 (a BIGINT UNSIGNED);
+INSERT INTO t1 VALUES (18446668621106209655);
+SELECT MAX(LENGTH(a)), LENGTH(MAX(a)), MIN(a), MAX(a), CONCAT(MIN(a)), CONCAT(MAX(a)) FROM t1;
+MAX(LENGTH(a))	LENGTH(MAX(a))	MIN(a)	MAX(a)	CONCAT(MIN(a))	CONCAT(MAX(a))
+20	20	18446668621106209655	18446668621106209655	18446668621106209655	18446668621106209655
+DROP TABLE t1;
+#
 End of 5.1 tests

mysql-test/t/func_group.test

@@ -1117,6 +1117,16 @@ SELECT RELEASE_LOCK('aaaaaaaaaaaaaaaaa');
 
 --enable_result_log
 
+
+--echo #
+--echo # Bug #11766094 - 59132: MIN() AND MAX() REMOVE UNSIGNEDNESS 
+--echo #
+
+CREATE TABLE t1 (a BIGINT UNSIGNED);
+INSERT INTO t1 VALUES (18446668621106209655);
+SELECT MAX(LENGTH(a)), LENGTH(MAX(a)), MIN(a), MAX(a), CONCAT(MIN(a)), CONCAT(MAX(a)) FROM t1;
+DROP TABLE t1;
+
 --echo #
 --echo End of 5.1 tests
 

sql/item.cc

@@ -7109,7 +7109,7 @@ String *Item_cache_int::val_str(String *str)
   DBUG_ASSERT(fixed == 1);
   if (!value_cached && !cache_value())
     return NULL;
-  str->set(value, default_charset());
+  str->set_int(value, unsigned_flag, default_charset());
   return str;
 }