followers in information_schema.placement_rules is not right when do not specify followers in placement

[lcwangchao]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create placement policy p1 constraints='[+region=r1]';
select policy_name,followers from information_schema.placement_rules where policy_name='p1';

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

followers should not be 0

3. What did you see instead (Required)

mysql> select policy_name,followers from information_schema.placement_rules where policy_name='p1';
+-------------+-----------+
| policy_name | followers |
+-------------+-----------+
| p1          |         0 |
+-------------+-----------+
1 row in set (0.00 sec)

4. What is your TiDB version? (Required)

master

mysql> select tidb_version();
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                                                                                   |
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v5.5.0-alpha
Edition: Community
Git Commit Hash: 706abd66aea261ed783f0771411e71d99ae1b32d
Git Branch: heads/refs/tags/v5.5.0-alpha
UTC Build Time: 2022-01-11 14:54:32
GoVersion: go1.16.4
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

[morgo]

For potential implementers: it might be easier to wait for #31698 to merge, since there will surely be conflicts.

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'fixes-x.y.z', and then remove 'needs-more-info' label.