Incorrect query result caused by LEFT/RIGHT JOIN about tidb HOT 3 OPEN

[16:14:44]TiDB root:test> SELECT * FROM (SELECT t0.c0, (TIMEDIFF('2003-07-13', '2007-06-25') AND true) IS TRUE AS flag FROM v0 LEFT JOIN t0 ON 1) AS t  where flag = 1;
+------------+------+
| c0         | flag |
+------------+------+
| 1.4013e-45 | 1    |
+------------+------+
1 row in set
Time: 0.004s
[16:14:52]TiDB root:test> SELECT * FROM (SELECT t0.c0, (TIMEDIFF('2003-07-13', '2007-06-25') AND true) IS TRUE AS flag FROM v0 LEFT JOIN t0 ON 1) AS t ;
+--------+------+
| c0     | flag |
+--------+------+
| <null> | 1    |
+--------+------+
1 row in set
Time: 0.004s
[16:15:00]TiDB root:test> explain SELECT * FROM (SELECT t0.c0, (TIMEDIFF('2003-07-13', '2007-06-25') AND true) IS TRUE AS flag FROM v0 LEFT JOIN t0 ON 1) AS t  where flag = 1;
+--------------------------+---------+-----------+---------------+---------------------------------------------------------------------------------------------------------------+
| id                       | estRows | task      | access object | operator info                                                                                                 |
+--------------------------+---------+-----------+---------------+---------------------------------------------------------------------------------------------------------------+
| Projection_12            | 2.56    | root      |               | test.t0.c0, istrue(and(istrue_with_null(cast(timediff(2003-07-13, 2007-06-25), double BINARY)), 1))->Column#5 |
| └─HashJoin_14            | 2.56    | root      |               | CARTESIAN left outer join                                                                                     |
|   ├─Selection_15(Build)  | 1.60    | root      |               | eq(istrue(and(istrue_with_null(cast(timediff("2003-07-13", "2007-06-25"), double BINARY)), 1)), 1)            |
|   │ └─TableReader_18     | 2.00    | root      |               | data:TableFullScan_17                                                                                         |
|   │   └─TableFullScan_17 | 2.00    | cop[tikv] | table:t0      | keep order:false                                                                                              |
|   └─Selection_19(Probe)  | 1.60    | root      |               | eq(istrue(and(istrue_with_null(cast(timediff("2003-07-13", "2007-06-25"), double BINARY)), 1)), 1)            |
|     └─TableReader_21     | 2.00    | root      |               | data:TableFullScan_20                                                                                         |
|       └─TableFullScan_20 | 2.00    | cop[tikv] | table:t0      | keep order:false                                                                                              |
+--------------------------+---------+-----------+---------------+---------------------------------------------------------------------------------------------------------------+
8 rows in set
Time: 0.004s
[16:15:10]TiDB root:test> explain SELECT * FROM (SELECT t0.c0, (TIMEDIFF('2003-07-13', '2007-06-25') AND true) IS TRUE AS flag FROM v0 LEFT JOIN t0 ON 1) AS t ;
+---------------------------+---------+-----------+---------------+---------------------------------------------------------------------------------------------------------------+
| id                        | estRows | task      | access object | operator info                                                                                                 |
+---------------------------+---------+-----------+---------------+---------------------------------------------------------------------------------------------------------------+
| Projection_8              | 4.00    | root      |               | test.t0.c0, istrue(and(istrue_with_null(cast(timediff(2003-07-13, 2007-06-25), double BINARY)), 1))->Column#5 |
| └─HashJoin_10             | 4.00    | root      |               | CARTESIAN left outer join                                                                                     |
|   ├─Projection_11(Build)  | 2.00    | root      |               | 1->Column#8                                                                                                   |
|   │ └─TableReader_13      | 2.00    | root      |               | data:TableFullScan_12                                                                                         |
|   │   └─TableFullScan_12  | 2.00    | cop[tikv] | table:t0      | keep order:false                                                                                              |
|   └─TableReader_15(Probe) | 2.00    | root      |               | data:TableFullScan_14                                                                                         |
|     └─TableFullScan_14    | 2.00    | cop[tikv] | table:t0      | keep order:false                                                                                              |
+---------------------------+---------+-----------+---------------+---------------------------------------------------------------------------------------------------------------+