The CTE inside of view can't determine whether it can be inlined

[elsa0520]

Bug Report

If the CTE is inside of view, optimizer can't determine whether it can be inlined by rule "The CTE is consumed only once. It can be inlined by default."

1. Minimal reproduce step (Required)

1. create view with cte1, cte2, cte3. The consumer count of CTE1 is 2, So it could not be inlined.

create view test_multi_consumer_cte as 
with cte1 as (select a from test), 
cte2 as (select a from cte1 where a=1), 
cte3 as (select cte1.a from cte1 join cte2 where cte1.a=2) 
select * from cte3;

2. query table

mysql> explain select * from test_multi_consumer_cte;
+------------------------------+----------+-----------+---------------+--------------------------------+
| id                           | estRows  | task      | access object | operator info                  |
+------------------------------+----------+-----------+---------------+--------------------------------+
| HashJoin_38                  | 100.00   | root      |               | CARTESIAN inner join           |
| ├─TableReader_45(Build)      | 10.00    | root      |               | data:Selection_44              |
| │ └─Selection_44             | 10.00    | cop[tikv] |               | eq(test.test.a, 1)             |
| │   └─TableFullScan_43       | 10000.00 | cop[tikv] | table:test    | keep order:false, stats:pseudo |
| └─TableReader_42(Probe)      | 10.00    | root      |               | data:Selection_41              |
|   └─Selection_41             | 10.00    | cop[tikv] |               | eq(test.test.a, 2)             |
|     └─TableFullScan_40       | 10000.00 | cop[tikv] | table:test    | keep order:false, stats:pseudo |
+------------------------------+----------+-----------+---------------+--------------------------------+
7 rows in set (0.00 sec)

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

The behavior should be seem as the query view directly

+---------------------------------+----------+-----------+---------------+--------------------------------------------+
| id                              | estRows  | task      | access object | operator info                              |
+---------------------------------+----------+-----------+---------------+--------------------------------------------+
| HashJoin_32                     | 256.00   | root      |               | CARTESIAN inner join                       |
| ├─Selection_36(Build)           | 16.00    | root      |               | eq(test.test.a, 1)                         |
| │ └─CTEFullScan_37              | 20.00    | root      | CTE:cte1      | data:CTE_0                                 |
| └─Selection_34(Probe)           | 16.00    | root      |               | eq(test.test.a, 2)                         |
|   └─CTEFullScan_35              | 20.00    | root      | CTE:cte1      | data:CTE_0                                 |
| CTE_0                           | 20.00    | root      |               | Non-Recursive CTE                          |
| └─TableReader_29(Seed Part)     | 20.00    | root      |               | data:Selection_28                          |
|   └─Selection_28                | 20.00    | cop[tikv] |               | or(eq(test.test.a, 2), eq(test.test.a, 1)) |
|     └─TableFullScan_27          | 10000.00 | cop[tikv] | table:test    | keep order:false, stats:pseudo             |
+---------------------------------+----------+-----------+---------------+--------------------------------------------+
9 rows in set (0.01 sec)

3. What did you see instead (Required)

The CTE1 is inlined which is incorrect , because it is consumed by CTE2 and CTE3.
The consumer count of CTE1 should be 2 more than 1. So it could not be inlined be default.

4. What is your TiDB version? (Required)

v8.1

[elsa0520]

The main reason

The preprocessor is used to compute the cte.consumercount

But, the query of view will skip this step which means the cte.consumercount inside of view will be always 0

This cause optimizer could not judge the "CTE inline by default"