MDEV-6868: MariaDB server crash ( select with union and order by with subquery )

Excluding ORDER BY condition should be done after preparation it (even to catch syntax errors).

1 files changed, 20 insertions, 0 deletions

diff --git a/mysql-test/r/union.result b/mysql-test/r/union.result
index 4ecac34d9fa..40f5a77e3d0 100644
--- a/mysql-test/r/union.result
+++ b/mysql-test/r/union.result
@@ -1935,3 +1935,23 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 3	UNION	t1	ALL	NULL	NULL	NULL	NULL	4	
 NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
 drop table t1;
+#
+# MDEV-6868:MariaDB  server crash ( select with union and order by
+# with subquery )
+#
+CREATE TABLE t1 ( id INTEGER, sample_name1 VARCHAR(100), sample_name2 VARCHAR(100), PRIMARY KEY(id) );
+INSERT INTO t1 ( id, sample_name1, sample_name2 ) VALUES ( 1, 'aaaa', 'bbbb' ), ( 2, 'cccc', 'dddd' );
+(
+SELECT sample_name1 AS testname FROM t1
+)
+UNION
+(
+SELECT sample_name2 AS testname FROM t1 C ORDER BY (SELECT T.sample_name1 FROM t1 T WHERE T.id = C.id)
+)
+;
+testname
+aaaa
+cccc
+bbbb
+dddd
+drop table t1;