MySQL Bugs: #121500: CTE omits a row from a GROUP BY WITH ROLLUP result

Bug #121500	CTE omits a row from a GROUP BY WITH ROLLUP result
Submitted:	14 Oct 7:42
Reporter:	jinxin gui	Email Updates:
Status:	Open	Impact on me:	None
Category:	MySQL Server: Optimizer	Severity:	S2 (Serious)
Version:	26.7.0	OS:	Linux
Assigned to:		CPU Architecture:	Any
Tags:	cte, rollup

Description:
Selecting directly from a GROUP BY ... WITH ROLLUP query returns two rows, but selecting from a CTE containing the same query returns only one. The CTE result is missing the row containing 7; only the NULL rollup row remains.

How to repeat:
Run the following in an empty schema:

CREATE TABLE t (f1 INT, pk INT NOT NULL, PRIMARY KEY (pk));
INSERT INTO t VALUES (7, 3);

SELECT f1 AS col1 FROM t WHERE pk = 3 GROUP BY f1 WITH ROLLUP ORDER BY f1;

WITH c AS (SELECT f1 AS col1 FROM t WHERE pk = 3 GROUP BY f1 WITH ROLLUP ORDER BY f1) SELECT col1 FROM c;

Actual result:

The first query returns two rows:

NULL
7

The second query returns only one row:

NULL

Expected result:

Both queries should return the same two rows, NULL and 7. Reading the query through a CTE should not remove the grouped row.