AutoID service client still used the old database id after `rename` for incremental diff load.

[YangKeao]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. Start a TiDB cluster:

tiup playground nightly

2. Create a database and a table with AUTO_ID_CACHE=1. Insert some rows into it, rename it to a new database.

mysql> use test;
Database changed

mysql> create table t(id int primary key auto_increment) AUTO_ID_CACHE=1;
Query OK, 0 rows affected (0.02 sec)

mysql> insert into t values ();
Query OK, 1 row affected (0.00 sec)

mysql> insert into t values ();
Query OK, 1 row affected (0.00 sec)

mysql> insert into t values ();
Query OK, 1 row affected (0.00 sec)

mysql> create database test2;
Query OK, 0 rows affected (0.02 sec)

mysql> alter table t rename test2.t;
Query OK, 0 rows affected (0.04 sec)

mysql> insert into test2.t values ();
Query OK, 1 row affected (0.00 sec)

3. Insert into test2.t with explicit id:

mysql> insert into test2.t values (100);
Query OK, 1 row affected (0.00 sec)

Read the tidb log, you'll find that it still used the old database id:

[2025/11/19 16:19:55.895 +08:00] [INFO] [autoid.go:194] ["alloc4Signed from"] [category="autoid service"] [dbID=112] [tblID=117] ["from base"=0] ["from end"=0] ["to base"=0] ["to end"=4000]

dbID=112 is test, but not test2. test2 is 119.

Now, the content of test2.t is:

mysql> select * from test2.t;
+-----+
| id  |
+-----+
|   1 |
|   2 |
|   3 |
|   4 |
| 100 |
+-----+
5 rows in set (0.00 sec)

4. Start a new TiDB and attach to this cluster, insert into t on this new TiDB:

mysql> insert into test2.t values ();
ERROR 1062 (23000): Duplicate entry '1' for key 't.PRIMARY'

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

1. Insert successfully.
2. The rebase should use new dbID.

3. What did you see instead (Required)

1. Dup key error.
2. The rebase still used old dbID.

I think it's related to the diff load schema. The allocator is not renewed after loading the diff when the db changed.

4. What is your TiDB version? (Required)

mysql> select tidb_version();
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                                             |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v9.0.0-beta.2.pre-309-g6499b2f
Edition: Community
Git Commit Hash: 6499b2ff017629efa9ec1f23e8260c53681e2314
Git Branch: HEAD
UTC Build Time: 2025-08-13 02:44:13
GoVersion: go1.23.12
Race Enabled: false
Check Table Before Drop: false
Store: tikv
Kernel Type: Classic |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

[YangKeao]

The workaround is to use ALTER TABLE t AUTO_INCREMENT = BIG_ENOUGH_VALUE. The existing tidb instance will also use new dbID after this DDL.

[joechenrh]

Maybe related to this, I forgot to rebase singlePointAlloc during applying schema diff 🥲 (For 8.5 and master)

tidb/pkg/meta/autoid/autoid_service.go

Lines 257 to 259 in 17945b9

	func (*singlePointAlloc) Transfer(_, _ int64) error {
	return nil
	}

If I change it to the following code, the result is OK

func (sp *singlePointAlloc) Transfer(databaseID, tableID int64) error {
	if sp.dbID == databaseID && sp.tblID == tableID {
		return nil
	}
	sp.dbID = databaseID
	sp.tblID = tableID
	return sp.Rebase(context.Background(), sp.lastAllocated+1, false)
}

MySQL [(none)]> insert into test2.t values ();
Query OK, 1 row affected (0.007 sec)

MySQL [(none)]> select * from test2.t;
+-----+
| id  |
+-----+
|   1 |
|   2 |
|   3 |
|   4 |
| 100 |
| 101 |
+-----+
6 rows in set (0.002 sec)

[YangKeao]

(For 8.5 and master)

@joechenrh so this bug only affects v8.5 and master, right? I didn't verify yet.

[joechenrh]

so this bug only affects v8.5 and master, right?

Seems like it's OK with v8.1.1, didn't test with other version.