MDEV-5719: Wrong result with GROUP BY and LEFT OUTER JOIN

Merged revision 5224 from mysql-5.6 and added a test case.
..
revno: 5224
committer: Sergey Glukhov <sergey.glukhov@oracle.com>
branch nick: mysql-5.6
timestamp: Wed 2013-06-19 14:24:08 +0400
message:
    Bug#16620047 INCORRECT QUERY RESULT (AFTER SERVER UPGRADE)

mysql-test/r/group_by_innodb.result

@@ -57,3 +57,26 @@ i	GROUP_CONCAT(  d1, d2 ORDER BY d1, d2 )
 NULL	11.1,22.2
 DROP TABLE t1;
 End of 5.5 tests
+#
+# MDEV-5719: Wrong result with GROUP BY and LEFT OUTER JOIN
+#
+CREATE TABLE t1 (oidGroup INT, oid INT PRIMARY KEY)ENGINE=INNODB;
+INSERT INTO t1 VALUES (1,1),(1,2),(1,3),(1,4);
+CREATE TABLE t2 (oid INT PRIMARY KEY)ENGINE=INNODB;
+INSERT INTO t2 VALUES (3);
+SELECT a.oidGroup, a.oid, b.oid FROM t1 a LEFT JOIN t2 b ON
+a.oid=b.oid WHERE a.oidGroup=1;
+oidGroup	oid	oid
+1	1	NULL
+1	2	NULL
+1	3	3
+1	4	NULL
+SELECT a.oidGroup, a.oid, b.oid FROM t1 a LEFT JOIN t2 b ON
+a.oid=b.oid WHERE a.oidGroup=1 GROUP BY a.oid;
+oidGroup	oid	oid
+1	1	NULL
+1	2	NULL
+1	3	3
+1	4	NULL
+DROP TABLE t1, t2;
+# End of tests

mysql-test/t/group_by_innodb.test

@@ -67,3 +67,22 @@ DROP TABLE t1;
 
 --echo End of 5.5 tests
 
+--echo #
+--echo # MDEV-5719: Wrong result with GROUP BY and LEFT OUTER JOIN
+--echo #
+CREATE TABLE t1 (oidGroup INT, oid INT PRIMARY KEY)ENGINE=INNODB;
+INSERT INTO t1 VALUES (1,1),(1,2),(1,3),(1,4);
+
+CREATE TABLE t2 (oid INT PRIMARY KEY)ENGINE=INNODB;
+INSERT INTO t2 VALUES (3);
+
+# Returns a value
+SELECT a.oidGroup, a.oid, b.oid FROM t1 a LEFT JOIN t2 b ON
+a.oid=b.oid WHERE a.oidGroup=1;
+
+SELECT a.oidGroup, a.oid, b.oid FROM t1 a LEFT JOIN t2 b ON
+a.oid=b.oid WHERE a.oidGroup=1 GROUP BY a.oid;
+
+DROP TABLE t1, t2;
+
+--echo # End of tests

sql/field.h

@@ -656,21 +656,28 @@ public:
   inline bool is_null(my_ptrdiff_t row_offset= 0) const
   {
     /*
+      If the field is NULLable, it returns NULLity based
+      on null_ptr[row_offset] value. Otherwise it returns
+      NULL flag depending on TABLE::null_row value.
+
       The table may have been marked as containing only NULL values
       for all fields if it is a NULL-complemented row of an OUTER JOIN
       or if the query is an implicitly grouped query (has aggregate
       functions but no GROUP BY clause) with no qualifying rows. If
-      this is the case (in which TABLE::null_row is true), the field
-      is considered to be NULL.
+      this is the case (in which TABLE::null_row is true) and the
+      field is not nullable, the field is considered to be NULL.
+
+      Do not change the order of testing. Fields may be associated
+      with a TABLE object without being part of the current row.
+      For NULL value check to work for these fields, they must
+      have a valid null_ptr, and this pointer must be checked before
+      TABLE::null_row.
+
       Note that if a table->null_row is set then also all null_bits are
       set for the row.
-
-      Otherwise, if the field is NULLable, it has a valid null_ptr
-      pointer, and its NULLity is recorded in the "null_bit" bit of
-      null_ptr[row_offset].
     */
-    return (table->null_row ? TRUE :
-            null_ptr ? MY_TEST(null_ptr[row_offset] & null_bit) : 0);
+    return real_maybe_null() ?
+      MY_TEST(null_ptr[row_offset] & null_bit) : table->null_row;
   }
   inline bool is_real_null(my_ptrdiff_t row_offset= 0) const
     { return null_ptr ? (null_ptr[row_offset] & null_bit ? 1 : 0) : 0; }