inconsistent SQL bind caches after recreating bind with different bind_sql for a same original_sql

[eurekaka]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Start 2 tidb-servers, execute create / drop binding statements on tidb-1, and observe the results of show global bindings on tidb-2.

This is the output on tidb-1, which is as expected.

mysql> create global binding for select * from t0 using select * from t0 use index(a);
Query OK, 0 rows affected (0.03 sec)

mysql> show global bindings;
+-------------------------+-------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
| Original_sql            | Bind_sql                            | Default_db | Status | Create_time             | Update_time             | Charset | Collation       | Source |
+-------------------------+-------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
| select * from test . t0 | SELECT * FROM test.t0 USE INDEX (a) | test       | using  | 2021-06-30 12:57:31.121 | 2021-06-30 12:57:31.121 | utf8    | utf8_general_ci | manual |
+-------------------------+-------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
1 row in set (0.00 sec)

mysql> create global binding for select * from t0 using select /*+ use_index(t0,a) */ * from t0;
Query OK, 0 rows affected (0.02 sec)

mysql> show global bindings;
+-------------------------+---------------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
| Original_sql            | Bind_sql                                    | Default_db | Status | Create_time             | Update_time             | Charset | Collation       | Source |
+-------------------------+---------------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
| select * from test . t0 | SELECT /*+ use_index(t0 a)*/ * FROM test.t0 | test       | using  | 2021-06-30 12:57:59.102 | 2021-06-30 12:57:59.102 | utf8    | utf8_general_ci | manual |
+-------------------------+---------------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
1 row in set (0.00 sec)

mysql> drop global binding for select * from t0;
Query OK, 0 rows affected (0.02 sec)

mysql> show global bindings;
Empty set (0.00 sec)

This is the output on tidb-2:

-- after the first create binding executed on tidb-1
mysql> show global bindings;
+-------------------------+-------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
| Original_sql            | Bind_sql                            | Default_db | Status | Create_time             | Update_time             | Charset | Collation       | Source |
+-------------------------+-------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
| select * from test . t0 | SELECT * FROM test.t0 USE INDEX (a) | test       | using  | 2021-06-30 12:57:31.121 | 2021-06-30 12:57:31.121 | utf8    | utf8_general_ci | manual |
+-------------------------+-------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
1 row in set (0.00 sec)

-- after the second create binding executed on tidb-1
mysql> show global bindings;
+-------------------------+---------------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
| Original_sql            | Bind_sql                                    | Default_db | Status | Create_time             | Update_time             | Charset | Collation       | Source |
+-------------------------+---------------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
| select * from test . t0 | SELECT * FROM test.t0 USE INDEX (a)         | test       | using  | 2021-06-30 12:57:31.121 | 2021-06-30 12:57:31.121 | utf8    | utf8_general_ci | manual |
| select * from test . t0 | SELECT /*+ use_index(t0 a)*/ * FROM test.t0 | test       | using  | 2021-06-30 12:57:59.102 | 2021-06-30 12:57:59.102 | utf8    | utf8_general_ci | manual |
+-------------------------+---------------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
2 rows in set (0.00 sec)

-- after the drop binding executed on tidb-1
mysql> show global bindings;
+-------------------------+-------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
| Original_sql            | Bind_sql                            | Default_db | Status | Create_time             | Update_time             | Charset | Collation       | Source |
+-------------------------+-------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
| select * from test . t0 | SELECT * FROM test.t0 USE INDEX (a) | test       | using  | 2021-06-30 12:57:31.121 | 2021-06-30 12:57:31.121 | utf8    | utf8_general_ci | manual |
+-------------------------+-------------------------------------+------------+--------+-------------------------+-------------------------+---------+-----------------+--------+
1 row in set (0.01 sec)

We can see that, tidb-2 has an invalid cached bind for use index(a) hint.

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

tidb-1 and tidb-2 have same cached bindings.

3. What did you see instead (Required)

tidb-2 has one more cached binding than tidb-1, which is expected to be removed.

4. What is your TiDB version? (Required)

4.0.12, master

[Reminiscent]

/assign

[ti-srebot]

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