Agg cannot pushdown to tiflash when there are expression index

[guo-shaoge]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. run following sql

drop table if exists t2;
create table t2(c1 int, c2 varchar(100));
insert into t2 values(1, 'xhy'), (2, 'abc');
alter table t2 set tiflash replica 1;

2. check tiflash_replica is avaiable.
3. add expression index

alter table t2 add index idx2((lower(c2)));

4. Use nth_paln to check all available plans:

explain select /*+ nth_plan(1) */ count(c1) from t2 where lower(c2) = 'abc';

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

Can generate plan that Agg can pushdown to tiflash.

3. What did you see instead (Required)

There is no plan that Selection and HashAgg pushdown to tiflash.

MySQL [test]> explain select /*+ nth_plan(2) */ count(c1) from t2 where lower(c2) = 'abc';
+------------------------------+----------+--------------+---------------+-----------------------------------+
| id                           | estRows  | task         | access object | operator info                     |
+------------------------------+----------+--------------+---------------+-----------------------------------+
| HashAgg_7                    | 1.00     | root         |               | funcs:count(test.t2.c1)->Column#5 |
| └─Selection_17               | 8000.00  | root         |               | eq(lower(test.t2.c2), "abc")      |
|   └─Projection_16            | 10000.00 | root         |               | test.t2.c1, lower(test.t2.c2)     |
|     └─TableReader_15         | 10000.00 | root         |               | data:TableFullScan_14             |
|       └─TableFullScan_14     | 10000.00 | cop[tiflash] | table:t2      | keep order:false, stats:pseudo    |
+------------------------------+----------+--------------+---------------+-----------------------------------+
5 rows in set (0.002 sec)

4. What is your TiDB version? (Required)

MySQL [test]> select tidb_version();
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                                               |
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v6.5.0
Edition: Community
Git Commit Hash: 77776e17159e9c6faf6aeedf3085a7a2524d3205
Git Branch: heads/refs/tags/v6.5.0
UTC Build Time: 2022-12-05 13:50:22
GoVersion: go1.19.3
Race Enabled: false
TiKV Min Version: 6.2.0-alpha
Check Table Before Drop: false
Store: tikv |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------