MDEV-15204: lag/lead function order list mandatory

mysql-test/r/win.result

@@ -3219,8 +3219,8 @@ DROP TABLE fv_test, fv_result;
 #
 CREATE TABLE t1 (a int);
 INSERT INTO t1 VALUES (0),(1),(2);
-SELECT LEAD(a) OVER (PARTITION BY a) as lead,
-a AND LEAD(a) OVER (PARTITION BY a) AS a_and_lead_part
+SELECT LEAD(a) OVER (PARTITION BY a ORDER BY a) as lead,
+a AND LEAD(a) OVER (PARTITION BY a ORDER BY a) AS a_and_lead_part
 FROM t1;
 lead	a_and_lead_part
 NULL	0

mysql-test/r/win_lead_lag.result

@@ -226,4 +226,15 @@ pk	a	b	a+b	lag(a + b) over (partition by a order by pk) + pk
 9	2	2	4	12
 10	2	0	2	14
 11	2	10	12	13
+#
+# MDEV-15204 - LAG function doesn't require ORDER BY in OVER clause
+#
+select pk,
+lag(pk, 1) over ()
+from t1;
+ERROR HY000: No order list in window specification for 'lag'
+select pk,
+lead(pk, 1) over ()
+from t1;
+ERROR HY000: No order list in window specification for 'lead'
 drop table t1;

mysql-test/t/win.test

@@ -2000,8 +2000,8 @@ DROP TABLE fv_test, fv_result;
 
 CREATE TABLE t1 (a int);
 INSERT INTO t1 VALUES (0),(1),(2);
-SELECT LEAD(a) OVER (PARTITION BY a) as lead,
-       a AND LEAD(a) OVER (PARTITION BY a) AS a_and_lead_part
+SELECT LEAD(a) OVER (PARTITION BY a ORDER BY a) as lead,
+       a AND LEAD(a) OVER (PARTITION BY a ORDER BY a) AS a_and_lead_part
 FROM t1;
 
 SELECT a OR LEAD(a) OVER (ORDER BY a) AS a_or_lead_order

mysql-test/t/win_lead_lag.test

@@ -107,4 +107,17 @@ select pk, a, b, a+b,
 from t1
 order by pk asc;
 
+--echo #
+--echo # MDEV-15204 - LAG function doesn't require ORDER BY in OVER clause
+--echo #
+--error ER_NO_ORDER_LIST_IN_WINDOW_SPEC
+select pk,
+       lag(pk, 1) over ()
+from t1;
+
+--error ER_NO_ORDER_LIST_IN_WINDOW_SPEC
+select pk,
+       lead(pk, 1) over ()
+from t1;
+
 drop table t1;

sql/item_windowfunc.h

@@ -792,6 +792,8 @@ class Item_window_func : public Item_func_or_sum
     case Item_sum::DENSE_RANK_FUNC:
     case Item_sum::PERCENT_RANK_FUNC:
     case Item_sum::CUME_DIST_FUNC:
+    case Item_sum::LAG_FUNC:
+    case Item_sum::LEAD_FUNC:
       return true;
     default: 
       return false;