tidb_row_checksum() calculate the returned value on the real time instead of previous stored value

[3AceShowHand]

Enhancement

At the moment, when use tidb_row_checksum() function return the checksum value which was calculated when the data inserted, this value may be stable since the table schema change.

create table t (a int primary key, b int);
insert into t values (1, 2);                         # assume the checksum is `123`

alter table t add column c int default 1; 

select tidb_row_checksum() from t where a = 1;  ## `123` is returned, but the real checksum may be `234`