Corruption on statement rollback when ON UPDATE SET NULL affects the base column

--source include/have_innodb.inc

# Bug#39147834 statement rollback on indexed virtual columns crashes when

# FK ON UPDATE SET NULL updates the parent key.

CREATE TABLE t18 (

  c5 INT NOT NULL,

  PRIMARY KEY (c5)

) ENGINE=InnoDB;

CREATE TABLE t21 (

  c1 INT NOT NULL,

  c2 INT DEFAULT NULL,

  c2v INT AS (c2 DIV 1), c1v INT AS (FLOOR(c1)),

  KEY i15 (c2v, c1v),

  CONSTRAINT t21_ibfk_1 FOREIGN KEY (c2) REFERENCES t18 (c5) ON UPDATE SET NULL

) ENGINE=InnoDB;

INSERT INTO t18 (c5) VALUES (1), (2);

INSERT INTO t21 (c1, c2) VALUES (0, 1);

# This first changes 1 to 3 and cascades c2 = 1 to c2 = NULL. Updating the

# second parent row (2 to 3) then hits the duplicate primary key. The whole

# statement must roll back, including the functional-index update in t21.

--error ER_DUP_ENTRY

UPDATE t18 SET c5 = 3;

SELECT c5 FROM t18 ORDER BY c5;

SELECT c1, c2 FROM t21;

DROP TABLE t21, t18;

# Bug#39872048: DELETE with ON DELETE SET NULL must preserve all functional

# index key parts when its effects are rolled back.

CREATE TABLE parent (

  id INT PRIMARY KEY

) ENGINE=InnoDB;

CREATE TABLE child (

  a INT DEFAULT NULL,

  parent_id INT DEFAULT NULL,

  KEY idx_functional ((IFNULL(a, 0)), (IFNULL(parent_id, 0))),

  CONSTRAINT fk_parent FOREIGN KEY (parent_id) REFERENCES parent (id)

    ON DELETE SET NULL

) ENGINE=InnoDB;

INSERT INTO parent VALUES (1);

INSERT INTO child VALUES (NULL, 1);

START TRANSACTION;

DELETE FROM parent WHERE id = 1;

ROLLBACK;

SELECT id FROM parent;

SELECT a, parent_id FROM child;

DROP TABLE child, parent;

2026-10-21 12:26:23 4 [ERROR] InnoDB: Record in index `i15` of table `test`.`t21` was not found on update: TUPLE (info_bits=0, 3 fields): {[4]    (0x80000001),NULL,[6]      (0x000000000200)} at: COMPACT RECORD(info_bits=0, 1 fields): {[8]infimum (0x696E66696D756D00)}

mariadbd: /mariadb/10.6/storage/innobase/row/row0upd.cc:1926: dberr_t row_upd_sec_index_entry(upd_node_t*, que_thr_t*): Assertion `0' failed.