Bug#11766270 59343: YEAR(4): INCORRECT RESULT AND VALGRIND WARNINGS WITH MIN/MAX, UNION

When we create temporary result table for UNION
incorrect max_length for YEAR field is used and
it leads to incorrect field value and incorrect
result string length as YEAR field value calculation
depends on field length.
The fix is to use underlying item max_length for
Item_sum_hybrid::max_length intialization.


mysql-test/r/func_group.result:
  test case
mysql-test/t/func_group.test:
  test case
sql/field.cc:
  added assert
sql/item_sum.cc:
  init Item_sum_hybrid::max_length with 
  use underlying item max_length for
  INT result type.

4 files changed, 26 insertions, 5 deletions

diff --git a/mysql-test/r/func_group.result b/mysql-test/r/func_group.result
index 69bce1c8bd8..b90eb2a4c0f 100644
--- a/mysql-test/r/func_group.result
+++ b/mysql-test/r/func_group.result
@@ -1746,4 +1746,15 @@ 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;
 #
+# Bug #11766270  59343: YEAR(4): INCORRECT RESULT AND VALGRIND WARNINGS WITH MIN/MAX, UNION
+#
+CREATE TABLE t1(f1 YEAR(4));
+INSERT INTO t1 VALUES (0000),(2001);
+(SELECT MAX(f1) FROM t1) UNION (SELECT MAX(f1) FROM t1);
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def				MAX(f1)	MAX(f1)	13	4	4	Y	32864	0	63
+MAX(f1)
+2001
+DROP TABLE t1;
+#
 End of 5.1 tests
diff --git a/mysql-test/t/func_group.test b/mysql-test/t/func_group.test
index 600b46fcde6..177a1ca2471 100644
--- a/mysql-test/t/func_group.test
+++ b/mysql-test/t/func_group.test
@@ -1128,5 +1128,17 @@ SELECT MAX(LENGTH(a)), LENGTH(MAX(a)), MIN(a), MAX(a), CONCAT(MIN(a)), CONCAT(MA
 DROP TABLE t1;
 
 --echo #
+--echo # Bug #11766270  59343: YEAR(4): INCORRECT RESULT AND VALGRIND WARNINGS WITH MIN/MAX, UNION
+--echo #
+
+CREATE TABLE t1(f1 YEAR(4));
+INSERT INTO t1 VALUES (0000),(2001);
+--enable_metadata
+(SELECT MAX(f1) FROM t1) UNION (SELECT MAX(f1) FROM t1);
+--disable_metadata
+DROP TABLE t1;
+
+
+--echo #
 --echo End of 5.1 tests
 
diff --git a/sql/field.cc b/sql/field.cc
index 1ad5e408e07..3707c5b056f 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -5467,6 +5467,7 @@ double Field_year::val_real(void)
 longlong Field_year::val_int(void)
 {
   ASSERT_COLUMN_MARKED_FOR_READ;
+  DBUG_ASSERT(field_length == 2 || field_length == 4);
   int tmp= (int) ptr[0];
   if (field_length != 4)
     tmp%=100;					// Return last 2 char
@@ -5479,6 +5480,7 @@ longlong Field_year::val_int(void)
 String *Field_year::val_str(String *val_buffer,
 			    String *val_ptr __attribute__((unused)))
 {
+  DBUG_ASSERT(field_length < 5);
   val_buffer->alloc(5);
   val_buffer->length(field_length);
   char *to=(char*) val_buffer->ptr();
diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index 2a8aea68f7a..c62738abac0 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -612,17 +612,13 @@ Item_sum_hybrid::fix_fields(THD *thd, Item **ref)
 
   switch (hybrid_type= item->result_type()) {
   case INT_RESULT:
-    max_length= 20;
-    break;
   case DECIMAL_RESULT:
+  case STRING_RESULT:
     max_length= item->max_length;
     break;
   case REAL_RESULT:
     max_length= float_length(decimals);
     break;
-  case STRING_RESULT:
-    max_length= item->max_length;
-    break;
   case ROW_RESULT:
   default:
     DBUG_ASSERT(0);