Thanks for the clarification. There is not automatically way to enlarge the length. And I think that is not the things should be done by the database itself. That's my own opinion. But I think it would be helpful to show a warning to DBA when the allocated value is close to the upper limit.
For the following question, the answer is in seconds. To enlarge the column length, TiDB just need to modify the meta data.
"how long does it take to enlarge a pk column using alter table on a database that has a significant fraction of 4 billion rows?"
For the following question, the answer is in seconds. To enlarge the column length, TiDB just need to modify the meta data. "how long does it take to enlarge a pk column using alter table on a database that has a significant fraction of 4 billion rows?"