Do not report error for placement rules that has an non-exist partition ID

[xhebox]

Development Task

It is a known issue. Placement rules are cached in memory, persisted in PD. drop table should drop placement rules attached to the table. But you may recover the table later and expect that placement rules will recover, too.

We solve that by delaying the deletion of placement rules, check #20575. But as we don't really drop the persisted rules in PD. TiDB will reload the deleted rules back when:

1. restart
2. DDL infoschema fullLoad/snapshot load

Then you met the error mysql root@127.0.0.1:(none)> select * from information_schema.placement_policy (1105, "Can't find partition by id 59")

The full reproduce instructions

# start TiUP and add some rules

mysql root@127.0.0.1:(none)> select * from information_schema.placement_policy
+-------------+-------------+---------+-------------+------------+----------------+------------+--------+----------+-------------------+
| GROUP_ID    | GROUP_INDEX | RULE_ID | SCHEMA_NAME | TABLE_NAME | PARTITION_NAME | INDEX_NAME | ROLE   | REPLICAS | CONSTRAINTS       |
+-------------+-------------+---------+-------------+------------+----------------+------------+--------+----------+-------------------+
| TiDB_DDL_59 | 3           | leader  | test        | t          | p0             | <null>     | leader | 1        | "-engine=tiflash" |
| TiDB_DDL_59 | 3           | voter   | test        | t          | p0             | <null>     | voter  | 3        | "-engine=tiflash" |
+-------------+-------------+---------+-------------+------------+----------------+------------+--------+----------+-------------------+
mysql root@127.0.0.1:(none)> drop table test.t
mysql root@127.0.0.1:(none)> select * from information_schema.placement_policy
+----------+-------------+---------+-------------+------------+----------------+------------+------+----------+-------------+
| GROUP_ID | GROUP_INDEX | RULE_ID | SCHEMA_NAME | TABLE_NAME | PARTITION_NAME | INDEX_NAME | ROLE | REPLICAS | CONSTRAINTS |
+----------+-------------+---------+-------------+------------+----------------+------------+------+----------+-------------+

# restart(scale-in + scale-out) the TiDB node

mysql root@127.0.0.1:(none)> select * from information_schema.placement_policy
(1105, "Can't find partition by id 59")

[xhebox]

/assign