Unexpected "Information schema is changed" when commits

[wjhuang2016]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

mysql> drop table t2, t1;
Query OK, 0 rows affected (0.04 sec)

mysql> create table t1(a int);
Query OK, 0 rows affected (0.01 sec)

mysql> insert into t1 values (1);
Query OK, 1 row affected (0.00 sec)

mysql> begin pessimistic;
Query OK, 0 rows affected (0.00 sec)

mysql> update t1 set a=a;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1  Changed: 0  Warnings: 0

/* session 2 */ mysql> create table t2(a int);
Query OK, 0 rows affected (0.00 sec)

mysql> commit;
ERROR 8028 (HY000): Information schema is changed during the execution of the statement(for example, table definition may be updated by other DDL ran in parallel). If you see this error often, try increasing `tidb_max_delta_schema_count`. [try again later]

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

Commit successfully.

3. What did you see instead (Required)

Information schema is changed during the execution of the statement

4. What is your TiDB version? (Required)

4.0 master

[wjhuang2016]

Besides,

mysql> create table t1(a int);
Query OK, 0 rows affected (0.00 sec)

mysql> insert into t1 values (1);
Query OK, 1 row affected (0.00 sec)

mysql> begin;
Query OK, 0 rows affected (0.00 sec)

mysql> update t1 set a=a;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1  Changed: 0  Warnings: 0

/* session 2 */ mysql> drop table t1;
Query OK, 0 rows affected (0.01 sec)

mysql> commit;
Query OK, 0 rows affected (0.00 sec)

[blacktear23]

Seems this is related to write.go updateRecord function, when there is nothing changed, it just return without call UpdateDeltaForTable to update TxnCtx.TableDeltaMap, so when commit, Commit function will got an empty tableID list and SchemaValidator will return ResultFail.

[ti-srebot]

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