SPM: the update time is inconsistent with the time zone

[ChenPeng2013]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

use test;
drop table if exists t;

set @@global.time_zone=UTC;
set @@time_zone=UTC;
select now();
create table t(a int);
create global binding for select * from t using select * from t;
select sleep(3);
show global bindings;
show status like 'last_plan_binding_update_time';
select now();

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

mysql> show global bindings;
+----------------------------+--------------------------+------------+--------+-------------------------+-------------------------+---------+-------------+--------+
| Original_sql               | Bind_sql                 | Default_db | Status | Create_time             | Update_time             | Charset | Collation   | Source |
+----------------------------+--------------------------+------------+--------+-------------------------+-------------------------+---------+-------------+--------+
| select * from `test` . `t` | SELECT * FROM `test`.`t` | test       | using  | 2021-08-27 19:00:01.711 | 2021-08-27 11:00:01.711 | utf8mb4 | utf8mb4_bin | manual |
+----------------------------+--------------------------+------------+--------+-------------------------+-------------------------+---------+-------------+--------+
1 row in set (0.01 sec)

mysql> show status like 'last_plan_binding_update_time';
+-------------------------------+-------------------------+
| Variable_name                 | Value                   |
+-------------------------------+-------------------------+
| last_plan_binding_update_time | 2021-08-27 11:00:01.711 |
+-------------------------------+-------------------------+
1 row in set (0.02 sec)

mysql> select now();
+---------------------+
| now()               |
+---------------------+
| 2021-08-27 11:00:04 |
+---------------------+
1 row in set (0.00 sec)

3. What did you see instead (Required)

mysql> show global bindings;
+----------------------------+--------------------------+------------+--------+-------------------------+-------------------------+---------+-------------+--------+
| Original_sql               | Bind_sql                 | Default_db | Status | Create_time             | Update_time             | Charset | Collation   | Source |
+----------------------------+--------------------------+------------+--------+-------------------------+-------------------------+---------+-------------+--------+
| select * from `test` . `t` | SELECT * FROM `test`.`t` | test       | using  | 2021-08-27 19:00:01.711 | 2021-08-27 19:00:01.711 | utf8mb4 | utf8mb4_bin | manual |
+----------------------------+--------------------------+------------+--------+-------------------------+-------------------------+---------+-------------+--------+
1 row in set (0.01 sec)

mysql> show status like 'last_plan_binding_update_time';
+-------------------------------+-------------------------+
| Variable_name                 | Value                   |
+-------------------------------+-------------------------+
| last_plan_binding_update_time | 2021-08-27 19:00:01.711 |
+-------------------------------+-------------------------+
1 row in set (0.02 sec)

mysql> select now();
+---------------------+
| now()               |
+---------------------+
| 2021-08-27 11:00:04 |
+---------------------+
1 row in set (0.00 sec)

4. What is your TiDB version? (Required)

Release Version: v5.2.0-alpha-744-g46da3ba55
Edition: Community
Git Commit Hash: 46da3ba5572f90f8b8473f6a87de10056935e65a
Git Branch: master
UTC Build Time: 2021-08-26 06:32:21
GoVersion: go1.16.2
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false

[Reminiscent]

/assign