Bug Report: Cascading a Set Null constraint on a multicol foreign key fails

[GuptaManan100]

Overview of the Issue

This bug was found by the fuzzer that is added in #13980.

=== RUN   TestFkFuzzTest/Unsharded_-_Single_Thread_-_Balanced_Inserts_and_Updates
    mysql.go:228: Vitess and MySQL are not erroring the same way.
        Vitess error: target: uks.0.primary: vttablet: rpc error: code = FailedPrecondition desc = Operand should contain 2 column(s) (errno 1241) (sqlstate 21000) (CallerID: userData1): Sql: "select cola, colb, cola, colb from fk_multicol_t17 where (cola, colb) in ::fkc_vals and (cola, colb) not in (:cola /* INT64 */, :colb /* INT64 */) for update", BindVars: {#maxLimit: "type:INT64 value:\"10001\""cola: "type:INT64 value:\"5\""colb: "type:INT64 value:\"2\""fkc_vals: "type:TUPLE values:{type:TUPLE values:{} values:{}}"id: "type:INT64 value:\"3\""} (errno 1241) (sqlstate 21000) during query: update fk_multicol_t16 set cola = 5, colb = 2 where id = 3
        MySQL error: <nil>
E0914 17:57:47.272051   65012 fk_fuzz_test.go:380] Failing query - update fk_multicol_t16 set cola = 5, colb = 2 where id = 3

We see that the SELECT query that the planner creates is failing.
The schema of the tables are as follows

/*        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
 */

Reproduction Steps

Create the tables with the given schema
Then, try running an update query as listed above

Binary Version

main

Operating System and Environment details

main

Log Fragments

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