Foreign key Rows Affected Error

[GuptaManan100]

Description

Related Issue(s)

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 68.42%. Comparing base (cf3acaa) to head (b526619). Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15779      +/-   ##
==========================================
+ Coverage   68.41%   68.42%   +0.01%     
==========================================
  Files        1558     1559       +1     
  Lines      196353   196514     +161     
==========================================
+ Hits       134337   134468     +131     
- Misses      62016    62046      +30     

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[GuptaManan100]

It was noticed that rearranging order of deletes and updates is actually incorrect and can lead to different results.

Here is an example for update reordering -

/*
 *        fk_multicol_t15
 *                    │
 *                    │
 *  On Delete Cascade │
 *  On Update Cascade │
 *                    │
 *                    ▼
 *        fk_multicol_t16
 *                    │
 * On Delete Set Null │
 * On Update Set Null │
 *                    │
 *                    ▼
 *        fk_multicol_t17──────────────────┐
 *                    │                    │
 *                    │                    │ On Delete Set Null
 *  On Delete Cascade │                    │ On Update Set Null
 *  On Update Cascade │                    │
 *                    │                    │
 *                    ▼                    ▼
 *        fk_multicol_t18      fk_multicol_t19
 */

mysql [localhost:8032] {msandbox} (fk_test) > insert into fk_multicol_t15(id, cola, colb) values (1, 7, 1), (2, 9, 1), (3, 12, 1);
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql [localhost:8032] {msandbox} (fk_test) > insert into fk_multicol_t16(id, cola, colb) values (1, 7, 1), (2, 9, 1), (3, 12, 1);
Query OK, 3 rows affected (0.01 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql [localhost:8032] {msandbox} (fk_test) > insert into fk_multicol_t17(id, cola, colb) values (1, 7, 1), (2, 9, 1);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql [localhost:8032] {msandbox} (fk_test) > insert into fk_multicol_t19(id, cola, colb) values (1, 7, 1);
Query OK, 1 row affected (0.01 sec)

mysql [localhost:8032] {msandbox} (fk_test) > update fk_multicol_t17 join fk_multicol_t15 m1 on m1.id = fk_multicol_t17.id set m1.cola = m1.id + 8, fk_multicol_t17.colb = 32 where m1.id < 3;
ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`fk_test`.`fk_multicol_t17`, CONSTRAINT `fk_multicol_t17_ibfk_1` FOREIGN KEY (`cola`, `colb`) REFERENCES `fk_multicol_t16` (`cola`, `colb`) ON DELETE SET NULL ON UPDATE SET NULL)

mysql [localhost:8032] {msandbox} (fk_test) > update fk_multicol_t15 m1 join fk_multicol_t17 on m1.id = fk_multicol_t17.id set m1.cola = m1.id + 8, fk_multicol_t17.colb = 32 where m1.id < 3;
Query OK, 4 rows affected (0.00 sec)
Rows matched: 4  Changed: 4  Warnings: 0

[GuptaManan100]

Similarly, here is an example where reordering deletes leads to different results -

create table fk_t17
(
    id bigint,
    col varchar(10),
    primary key (id),
    index(col)
) Engine = InnoDB;

create table fk_t18
(
    id bigint,
    col varchar(10),
    primary key (id),
    index(col),
    foreign key (col) references fk_t17(col) on delete set null on update set null
) Engine = InnoDB;

create table fk_t19
(
    id bigint,
    col varchar(10),
    primary key (id),
    index(col),
    foreign key (col) references fk_t18(col) on delete restrict on update cascade
) Engine = InnoDB;

mysql [localhost:8032] {msandbox} (temp) > insert into fk_t17 values (1, 1);
Query OK, 1 row affected (0.01 sec)

mysql [localhost:8032] {msandbox} (temp) > insert into fk_t18 values (1, 1);
Query OK, 1 row affected (0.00 sec)

mysql [localhost:8032] {msandbox} (temp) > insert into fk_t19 values (1, 1);
Query OK, 1 row affected (0.00 sec)

mysql [localhost:8032] {msandbox} (temp) > delete fk_t18, fk_t17 from fk_t18 join fk_t17 using (id) where fk_t18.id = 1;
ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails (`temp`.`fk_t19`, CONSTRAINT `fk_t19_ibfk_1` FOREIGN KEY (`col`) REFERENCES `fk_t18` (`col`) ON DELETE RESTRICT ON UPDATE CASCADE)
mysql [localhost:8032] {msandbox} (temp) > delete fk_t17, fk_t18 from fk_t17 join fk_t18 using (id) where fk_t18.id = 1;
Query OK, 2 rows affected (0.00 sec)

[GuptaManan100]

Closing the PR because of the issues pointed ⬆️