error on large number with type bigint

[hicqu]

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
   If possible, provide a recipe for reproducing the error.

create table x (a bigint);
insert into x values(pow(2, 63)-1);
select * from x;

2. What did you expect to see?

mysql> select * from x;
Field   1:  `a`
Catalog:    `def`
Database:   `test`
Table:      `x`
Org_table:  `x`
Type:       LONGLONG
Collation:  binary (63)
Length:     20
Max_length: 19
Decimals:   0
Flags:      NUM


+---------------------+
| a                   |
+---------------------+
| 9223372036854775807 |
+---------------------+

3. What did you see instead?

mysql> select * from x;
Field   1:  `a`
Catalog:    `def`
Database:   ``
Table:      `x`
Org_table:  ``
Type:       LONGLONG
Collation:  binary (63)
Length:     21
Max_length: 20
Decimals:   31
Flags:      BINARY NUM


+----------------------+
| a                    |
+----------------------+
| -9223372036854775808 |
+----------------------+

4. What version of TiDB are you using (tidb-server -V)?
   latest master branch.

[hicqu]

The first output is from mysql 5.7.18