WHERE x > ALL returns rows for which the identical projected predicate is false

Description

MariaDB Server 12.3.2 returns an extra row for `x > ALL` over a UNION of an integer column and an empty BLOB operand. With integer values 9 and 86 in the subquery, the WHERE form incorrectly accepts x=50. Projecting the identical predicate returns false for 50 and true for 90.

Casting the empty BLOB operand to a numeric type, or removing that operand, returns only the correct row. The observations suggest an interaction between set-operation output coercion and the WHERE evaluation path; no source debugging has established the internal cause.

How to repeat

CREATE TEMPORARY TABLE all_nums (v INT);

INSERT INTO all_nums VALUES (9),(86);

CREATE TEMPORARY TABLE all_binary (b BLOB);

INSERT INTO all_binary VALUES ('0');

CREATE TEMPORARY TABLE all_outer (x INT);

INSERT INTO all_outer VALUES (50),(90);

SELECT x FROM all_outer WHERE x>ALL(

    SELECT v FROM all_nums UNION SELECT b FROM all_binary WHERE FALSE

);

Expected result

Only x=90. The second UNION operand contributes no rows. 50 is not greater than 86, while 90 is greater than both 9 and 86.

Actual result

Two rows: x=50 and x=90.