Missing RootTaskType for agg causes Can't find a proper physical plan error(2)

[AilinKid]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

this issue seems similar as #38478 at the very first sight, but after digging deep inside, we found it has something related with virtual-column

CREATE TABLE `tai1` (
  `aid` int(11) DEFAULT NULL,
  `rid` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin 

CREATE TABLE `tai2` (
  `rid` int(11) DEFAULT NULL,
  `prilan` varchar(20) DEFAULT NULL,
  KEY `idx` ((lower(`prilan`)))
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin 

set both tables tiflash replica 1/ or mock the getPossiblePath in tidb code

alter table tai2 add index idx((lower(prilan)));  // important

set @@tidb_opt_distinct_agg_push_down = 1;

select count(distinct tai1.aid) as cb from tai1 inner join tai2 on tai1.rid = tai2.rid where lower(prilan)  LIKE LOWER('%python%');
(1815, "Internal : Can't find a proper physical plan for this query")

The important thing is that there is a expression-index side table of tai2

 KEY `idx` ((lower(`prilan`)))
which will create a hidden virtual column as lower(`prilan`)

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

show the plan out

3. What did you see instead (Required)

(1815, "Internal : Can't find a proper physical plan for this query")

4. What is your TiDB version? (Required)

master