Wrong default value for integer type

[Lloyd-Pottiger]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Wrong default value for integer type cause error in tiflash: pingcap/tiflash#3157

mysql test> create table t (a int);
-- The type of column i is int, but the default value is set to "0.00"
mysql test> alter table t add column i int not null default 0.00; 
mysql test> show create table t;

2. What did you expect to see? (Required)

+-------+-------------------------------------------------------------+
| Table | Create Table                                                |
+-------+-------------------------------------------------------------+
| t     | CREATE TABLE `t` (                                          |
|       |   `a` int(11) DEFAULT NULL,                                 |
|       |   `i` int(11) NOT NULL DEFAULT '0'                       |
|       | ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin |
+-------+-------------------------------------------------------------+

3. What did you see instead (Required)

+-------+-------------------------------------------------------------+
| Table | Create Table                                                |
+-------+-------------------------------------------------------------+
| t     | CREATE TABLE `t` (                                          |
|       |   `a` int(11) DEFAULT NULL,                                 |
|       |   `i` int(11) NOT NULL DEFAULT '0.00'                       |
|       | ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin |
+-------+-------------------------------------------------------------+

4. What is your TiDB version? (Required)

master

[Lloyd-Pottiger]

/component parser

[Lloyd-Pottiger]

mainly due to https://github.com/pingcap/tidb/blob/master/parser/model/model.go#L242, we set the c.DefaultValue = value directly in which value is in type of string. But when we check default value https://github.com/pingcap/tidb/blob/master/ddl/ddl_api.go#L1307-L1332
we will convert it into int

[Lloyd-Pottiger]

/assign

[Lloyd-Pottiger]

add another case:

test> create table td ( a int default 1.9, b int);
Query OK, 0 rows affected
Time: 0.079s
test> show create table td;
+-------+--------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                               |
+-------+--------------------------------------------------------------------------------------------------------------------------------------------+
| td    | CREATE TABLE `td` (\n  `a` int(11) DEFAULT '2',\n  `b` int(11) DEFAULT NULL\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin |
+-------+--------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set
Time: 0.018s

[seiya-annie]

/found customer