Persistent virtual column cannot cope with auto_increment column

If a persistent computed column uses an auto_increment column in its defining expression, upon inserting a new row into the table the value of the auto_increment column is taken to be zero and not the value it gets automatically assigned. The same problem does not happen with a virtual computed column.

Example:

create table test (a int key auto_increment, b int as(a) persistent);

insert test set a=null;

select * from test;

+---+------+

| a | b    |

+---+------+

| 1 |    0 |

+---+------+

One would, however, expect that b is 1, just like a. As it stands, persistent computed columns cannot meaningfully use auto_increment columns.