Fixed bug mdev-9976.

This bug happens due to a conflict in the construct window_spec.
(win_ref conflicts with the non-reserved key word ROWS).
The standard SQL-2003 says that ROWS is a reserved key word.
Made this key word reserved in our grammar and removed
the conflict.

mysql-test/r/win.result

@@ -2398,3 +2398,37 @@ SELECT * FROM t1 WHERE i IN ( SELECT COUNT(*) OVER (PARTITION BY c) FROM t2 );
 i
 1
 DROP TABLE t1, t2;
+#
+# MDEV-9976: window function without PARTITION BY and ORDER BY
+#
+CREATE TABLE t1  (id int, a int);
+INSERT INTO t1 VALUES
+(1,1000), (2,1100), (3,1800), (4,1500), (5,1700), (6,1200),
+(7,2000), (8,2100), (9,1600);
+SELECT id, sum(a) OVER (PARTITION BY id 
+ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)
+FROM t1;
+id	sum(a) OVER (PARTITION BY id 
+1	1000
+2	1100
+3	1800
+4	1500
+5	1700
+6	1200
+7	2000
+8	2100
+9	1600
+ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)
+SELECT id, sum(a) OVER (ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)
+FROM t1;
+id	sum(a) OVER (ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)
+1	14000
+2	13000
+3	5900
+4	10700
+5	7600
+6	11900
+7	4100
+8	2100
+9	9200
+DROP TABLE t1;

mysql-test/t/win.test

@@ -1442,3 +1442,24 @@ SELECT COUNT(*) OVER (PARTITION BY c) FROM t2;
 SELECT * FROM t1 WHERE i IN ( SELECT COUNT(*) OVER (PARTITION BY c) FROM t2 );
 
 DROP TABLE t1, t2;
+
+--echo #
+--echo # MDEV-9976: window function without PARTITION BY and ORDER BY
+--echo #
+
+CREATE TABLE t1  (id int, a int);
+INSERT INTO t1 VALUES
+ (1,1000), (2,1100), (3,1800), (4,1500), (5,1700), (6,1200),
+ (7,2000), (8,2100), (9,1600);
+
+--sorted_result
+SELECT id, sum(a) OVER (PARTITION BY id 
+                       ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)
+FROM t1;
+
+--sorted_result
+SELECT id, sum(a) OVER (ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)
+FROM t1;
+
+DROP TABLE t1;
+

sql/lex.h

@@ -517,8 +517,8 @@ static SYMBOL symbols[] = {
   { "ROLLUP",		SYM(ROLLUP_SYM)},
   { "ROUTINE",		SYM(ROUTINE_SYM)},
   { "ROW",		SYM(ROW_SYM)},
-  { "ROW_COUNT",        SYM(ROW_COUNT_SYM)},
   { "ROWS",		SYM(ROWS_SYM)},
+  { "ROW_COUNT",        SYM(ROW_COUNT_SYM)},
   { "ROW_FORMAT",	SYM(ROW_FORMAT_SYM)},
   { "RTREE",		SYM(RTREE_SYM)},
   { "SAVEPOINT",	SYM(SAVEPOINT_SYM)},

sql/sql_yacc.yy

@@ -1021,10 +1021,10 @@ bool my_yyoverflow(short **a, YYSTYPE **b, ulong *yystacksize);
 %parse-param { THD *thd }
 %lex-param { THD *thd }
 /*
-  Currently there are 103 shift/reduce conflicts.
+  Currently there are 102 shift/reduce conflicts.
   We should not introduce new conflicts any more.
 */
-%expect 103
+%expect 102
 
 /*
    Comments for TOKENS.
@@ -1535,10 +1535,10 @@ bool my_yyoverflow(short **a, YYSTYPE **b, ulong *yystacksize);
 %token  ROLLBACK_SYM                  /* SQL-2003-R */
 %token  ROLLUP_SYM                    /* SQL-2003-R */
 %token  ROUTINE_SYM                   /* SQL-2003-N */
-%token  ROWS_SYM                      /* SQL-2003-R */
-%token  ROW_FORMAT_SYM
 %token  ROW_SYM                       /* SQL-2003-R */
+%token  ROWS_SYM                      /* SQL-2003-R */
 %token  ROW_COUNT_SYM                 /* SQL-2003-N */
+%token  ROW_FORMAT_SYM
 %token  ROW_NUMBER_SYM
 %token  RTREE_SYM
 %token  SAVEPOINT_SYM                 /* SQL-2003-R */
@@ -14835,7 +14835,6 @@ keyword_sp:
         | ROLE_SYM                 {}
         | ROLLUP_SYM               {}
         | ROUTINE_SYM              {}
-        | ROWS_SYM                 {}
         | ROW_COUNT_SYM            {}
         | ROW_FORMAT_SYM           {}
         | ROW_SYM                  {}