Bug #120311 Wrong result for grouped SUM(DISTINCT ...) with DENSE_RANK() after view extraction

Description:
MySQL 9.6 returns different results for two logically equivalent grouped/window queries when the grouped aggregate is extracted into a view.

The issue appears in a window-function workload that combines SUM(DISTINCT ...), GROUP BY, and DENSE_RANK() OVER (...). In the reproduced case, the direct grouped/window query returns NULL for the aggregate column, while the logically equivalent view-based form returns 4.

Because the view definition is just the grouped aggregate projected with its grouping column, both queries should return the same col_2 value.

How to repeat:
DROP DATABASE IF EXISTS t1;
CREATE DATABASE t1;
USE t1;

CREATE TABLE t1 (
  c1 INT NOT NULL,
  c6 CHAR(2) NOT NULL
);

CREATE UNIQUE INDEX idx_t1_c1 ON t1 (c1);
CREATE INDEX idx_t1_c6 ON t1 (c6);

INSERT INTO t1 VALUES (4, 'z!');

SELECT SUM(DISTINCT c1) AS col_2,
       DENSE_RANK() OVER (ORDER BY c6 DESC) AS col_3
FROM t1
GROUP BY c6;

CREATE VIEW V_t1_06 AS
SELECT SUM(DISTINCT c1) AS col_2,
       c6
FROM t1
GROUP BY c6;

SELECT col_2,
       DENSE_RANK() OVER (ORDER BY c6 DESC) AS col_3
FROM V_t1_06;

Expected result:
+-------+-------+
| col_2 | col_3 |
+-------+-------+
|     4 |     1 |
+-------+-------+

Actual result:

-- original query
+-------+-------+
| col_2 | col_3 |
+-------+-------+
|  NULL |     1 |
+-------+-------+

-- transformed query
+-------+-------+
| col_2 | col_3 |
+-------+-------+
|     4 |     1 |
+-------+-------+

Hi QiFan Liu,

Thank you for the test case. Verified as described.