tidb_enforce_mpp cannot force using the tiflash #65145
Description
Bug Report
Please answer these questions before submitting your issue. Thanks!
1. Minimal reproduce step (Required)
create table t1(a int primary key, b int);
create table t2(a int primary key, b int);
alter table t1 set tiflash replica 1;
alter table t2 set tiflash replica 1;
select /*+ set_var(tidb_isolation_read_engines='tidb,tiflash'),set_var(tidb_enforce_mpp=on) */ * from t1 join t2 on t1.a=t2.b where t1.a in (1,2);
2. What did you expect to see? (Required)
TableReader root MppVersion: 3, data:ExchangeSender
└─ExchangeSender mpp[tiflash] ExchangeType: PassThrough
└─HashJoin mpp[tiflash] inner join, equal:[eq(test.t1.a, test.t2.b)]
├─ExchangeReceiver(Build) mpp[tiflash]
│ └─ExchangeSender mpp[tiflash] ExchangeType: Broadcast, Compression: FAST
│ └─TableRangeScan mpp[tiflash] table:t1 range:[1,1], [2,2], keep order:false, stats:pseudo
└─TableFullScan(Probe) mpp[tiflash] table:t2 pushed down filter:in(test.t2.b, 1, 2), not(isnull(test.t2.b)), keep order:false, stats:pseudo
3. What did you see instead (Required)
+---------------------------------+----------+--------------+---------------+----------------------------------------------+
| id | estRows | task | access object | operator info |
+---------------------------------+----------+--------------+---------------+----------------------------------------------+
| HashJoin_21 | 2.50 | root | | inner join, equal:[eq(test.t1.a, test.t2.b)] |
| ├─Batch_Point_Get_28(Build) | 2.00 | root | table:t1 | handle:[1 2], keep order:false, desc:false |
| └─TableReader_27(Probe) | 20.00 | root | | data:Selection_26 |
| └─Selection_26 | 20.00 | cop[tiflash] | | in(test.t2.b, 1, 2), not(isnull(test.t2.b)) |
| └─TableFullScan_25 | 10000.00 | cop[tiflash] | table:t2 | keep order:false, stats:pseudo |
+---------------------------------+----------+--------------+---------------+----------------------------------------------+