Duplicate entry when using BR to restore a AUTO_ID_CACHE=1 table

[tiancaiamao]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

tiup playground --tiflash 0
mysql -h 127.0.0.1 -u root -P 4000
create table t (a int primary key auto_increment, b int) AUTO_ID_CACHE 1;
insert into t(b) values (1),(2),(3),(4),(5),(6),(7),(8),(9);
insert into t(b) values (11),(21),(31),(41),(51),(61),(71),(81),(91);
...

tiup br backup full --pd=127.0.0.1:2379 -s local:///tmp/tidb/backup/tidb-test
# Ctrl + C to kill the playground cluster, and start a new one
tiup playground --tiflash 0

tiup br restore full --pd=127.0.0.1:2379 -s local:///tmp/tidb/backup/tidb-test

# insert data to the BR restored table
mysql -h 127.0.0.1 -u root -P 4000
use test
insert into t (b)  values  (666)

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

No error

3. What did you see instead (Required)

mysql> insert into t (b) values (666);
ERROR 1062 (23000): Duplicate entry '1' for key 't.PRIMARY'

4. What is your TiDB version? (Required)

7.1

[tiancaiamao]

AUTO_ID_CACHE=1 is introduced in v6.4, this bug affect that version above.

[bolt-leandro]

Thanks for opening this bug! Looking forward to a fix.