TiDB should use separated Allocators for the auto_increment column value and the row ID

[zimulala]

execute SQL statements as follows:

create table t (c int auto_increment, key(c));
insert into t values();
insert into t values();
select * from t;

tidb result:

+---+
| c |
+---+
| 1 |
| 3 |
+---+

mysql result:

+---+
| c |
+---+
| 1 |
| 2 |
+---+

[morgo]

For now, Auto_increment behavior in TiDB is documented as incompatible with MySQL.

[tisonkun]

@zimulala shall this issue be closed?

[tisonkun]

well I can see that #20708 is trying to fix this.

[bb7133]

This behavior was by-designed and I do not treat it as a bug, change it to 'enhancement' and track in #20708

[dragonly]

This can be reproduced in v5.3.0-alpha-1660-gdac5a6874.

[tangenta]

@dragonly The last PR is still not merged. So the behavior is expected.