Output is different from mysql where clause used in with dual table

[Alkaagr81]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

CREATE TABLE t1 (id int NOT NULL,c1 int NOT NULL,c2 int,
PRIMARY KEY(id),INDEX c1_c2_idx(c1, c2));
INSERT INTO t1 (id, c1, c2) VALUES (1,1,1), (2,2,2), (10,10,1), (11,10,8),
(12,10,1), (13,10,2); 
SELECT DISTINCT c1 FROM t1 WHERE 1 IN (2, (SELECT 1 FROM DUAL WHERE (c2 = 2)), 3);
SELECT DISTINCT c1 FROM t1 IGNORE INDEX (c1_c2_idx) WHERE EXISTS (SELECT * FROM DUAL WHERE (c2 = 2));

2. What did you expect to see? (Required)

mysql> CREATE TABLE t1 (id int NOT NULL,c1 int NOT NULL,c2 int,
    -> PRIMARY KEY(id),INDEX c1_c2_idx(c1, c2));
Query OK, 0 rows affected (0.02 sec)

mysql> INSERT INTO t1 (id, c1, c2) VALUES (1,1,1), (2,2,2), (10,10,1), (11,10,8),
    -> (12,10,1), (13,10,2); 
Query OK, 6 rows affected (0.00 sec)
Records: 6  Duplicates: 0  Warnings: 0

mysql> SELECT DISTINCT c1 FROM t1 WHERE 1 IN (2, (SELECT 1 FROM DUAL WHERE (c2 = 2)), 3);
+----+
| c1 |
+----+
|  2 |
| 10 |
+----+
2 rows in set (0.00 sec)

mysql> SELECT DISTINCT c1 FROM t1 IGNORE INDEX (c1_c2_idx) WHERE EXISTS (SELECT * FROM DUAL WHERE (c2 = 2));
+----+
| c1 |
+----+
|  2 |
| 10 |
+----+
2 rows in set (0.00 sec)

3. What did you see instead (Required)

mysql> CREATE TABLE t1 (id int NOT NULL,c1 int NOT NULL,c2 int,
    -> PRIMARY KEY(id),INDEX c1_c2_idx(c1, c2));
Query OK, 0 rows affected (0.01 sec)

mysql> INSERT INTO t1 (id, c1, c2) VALUES (1,1,1), (2,2,2), (10,10,1), (11,10,8),
    -> (12,10,1), (13,10,2); 
Query OK, 6 rows affected (0.01 sec)
Records: 6  Duplicates: 0  Warnings: 0

mysql> SELECT DISTINCT c1 FROM t1 WHERE 1 IN (2, (SELECT 1 FROM DUAL WHERE (c2 = 2)), 3);
+----+
| c1 |
+----+
|  2 |
|  1 |
| 10 |
+----+
3 rows in set (0.01 sec)

mysql> SELECT DISTINCT c1 FROM t1 IGNORE INDEX (c1_c2_idx) WHERE EXISTS (SELECT * FROM DUAL WHERE (c2 = 2));
ERROR 1051 (42S02): Unknown table ''

4. What is your TiDB version? (Required)

| Release Version: v5.4.0-alpha-184-g51f53f337-dirty
Edition: Community
Git Commit Hash: 51f53f3376bd548b302f654d6c11096f89119145
Git Branch: master
UTC Build Time: 2021-11-23 02:51:51
GoVersion: go1.16.9
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |

[zanmato1984]

I can't reproduce the first case:

+----+
| c1 |
+----+
|  2 |
| 10 |
+----+

Maybe it's been fixed by some other PR targeting some other bug.

However case 2 still exists. I'd change the label to route it to planner team.

[qw4990]

A minimum reproducible case:

mysql> select * from dual;
ERROR 1051 (42S02): Unknown table ''

The reason is that dual is a virtual table that has no column, MySQL returns a similar error when executing this query:

mysql> select * from dual;
ERROR 1096 (HY000): No tables used

This error seems acceptable in this case, degrade this issue from Major to Minor.