parallel apply does not work with mpp

[windtalker]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

mysql> drop table if exists test.t;
mysql> create table test.t (a int, b int);
mysql> alter table test.t set tiflash replica 1;
mysql> insert into test.t values(1,2),(2,1),(10,15),(15,10),(20,25),(25,10),(18,19),(19,18);
mysql> insert into test.t select a + 5, b + 5 from test.t;
mysql> insert into test.t select a + 5, b + 5 from test.t;
mysql> insert into test.t select a + 5, b + 5 from test.t;
mysql> insert into test.t select a + 5, b + 5 from test.t;
mysql> insert into test.t select a + 5, b + 5 from test.t;
mysql> insert into test.t select a + 5, b + 5 from test.t;
mysql> insert into test.t select a + 5, b + 5 from test.t;
mysql> insert into test.t select a + 5, b + 5 from test.t;
mysql> insert into test.t select a + 5, b + 5 from test.t;

mysql> explain select count(*) from t where a > (select a from t t1 where t.a > t1.a limit 1);
+--------------------------------------+---------+--------------+---------------+----------------------------------------------------------+
| id                                   | estRows | task         | access object | operator info                                            |
+--------------------------------------+---------+--------------+---------------+----------------------------------------------------------+
| HashAgg_15                           | 1.00    | root         |               | funcs:count(1)->Column#7                                 |
| └─Apply_18                           | 4091.90 | root         |               | CARTESIAN inner join, other cond:gt(test.t.a, test.t.a)  |
|   ├─TableReader_25(Build)            | 4091.90 | root         |               | MppVersion: 2, data:ExchangeSender_24                    |
|   │ └─ExchangeSender_24              | 4091.90 | mpp[tiflash] |               | ExchangeType: PassThrough                                |
|   │   └─Selection_23                 | 4091.90 | mpp[tiflash] |               | not(isnull(test.t.a))                                    |
|   │     └─TableFullScan_22           | 4096.00 | mpp[tiflash] | table:t       | pushed down filter:empty, keep order:false, stats:pseudo |
|   └─Selection_26(Probe)              | 3273.52 | root         |               | not(isnull(test.t.a))                                    |
|     └─Limit_29                       | 4091.90 | root         |               | offset:0, count:1                                        |
|       └─TableReader_39               | 4091.90 | root         |               | MppVersion: 2, data:ExchangeSender_38                    |
|         └─ExchangeSender_38          | 4091.90 | mpp[tiflash] |               | ExchangeType: PassThrough                                |
|           └─Limit_37                 | 4091.90 | mpp[tiflash] |               | offset:0, count:1                                        |
|             └─Selection_36           | 4091.90 | mpp[tiflash] |               | gt(test.t.a, test.t.a)                                   |
|               └─TableFullScan_35     | 5114.88 | mpp[tiflash] | table:t1      | pushed down filter:empty, keep order:false, stats:pseudo |
+--------------------------------------+---------+--------------+---------------+----------------------------------------------------------+
mysql> set tidb_enable_parallel_apply=0;
mysql> select count(*) from t where a > (select a from t t1 where t.a > t1.a limit 1);
+----------+
| count(*) |
+----------+
|     4095 |
+----------+
1 row in set (0.78 sec)
mysql> set tidb_enable_parallel_apply=1;
mysql> select count(*) from t where a > (select a from t t1 where t.a > t1.a limit 1);
+----------+
| count(*) |
+----------+
|        0 |
+----------+
1 row in set (0.78 sec)

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

When enable parallel apply, the query return correct result

3. What did you see instead (Required)

When enable parallel apply, query result is wrong

4. What is your TiDB version? (Required)

master@ 90dabc0