Default value of string like field can be empty string "" or "null"

[fishead]

fix issue #625

[a8m]

Looks good! Thanks for the contribution @fishead ❤️ 🙏

[a8m]

I'll check why the CI is failing and will update you.

[a8m]

MariaDB renders the NULL default values as NULL string, I'll dig into this and will update. See COLUMN_DEFAULT and COLUMN_DEFAULT IS NULL:

SELECT `TABLE_NAME`, `COLUMN_NAME`, `COLUMN_TYPE`, `COLUMN_COMMENT`, `IS_NULLABLE`, `COLUMN_KEY`, `COLUMN_DEFAULT` IS NULL, `COLUMN_DEFAULT`, `EXTRA`, `CHARACTER_SET_NAME`, `COLLATION_NAME` FROM `INFORMATION_SCHEMA`.`COLUMNS` WHERE `TABLE_SCHEMA` = 'test' AND `TABLE_NAME` = 'pets' ORDER BY `ORDINAL_POSITION`;
+------------+-------------+-------------+----------------+-------------+------------+--------------------------+----------------+-------+--------------------+----------------+
| TABLE_NAME | COLUMN_NAME | COLUMN_TYPE | COLUMN_COMMENT | IS_NULLABLE | COLUMN_KEY | `COLUMN_DEFAULT` IS NULL | COLUMN_DEFAULT | EXTRA | CHARACTER_SET_NAME | COLLATION_NAME |
+------------+-------------+-------------+----------------+-------------+------------+--------------------------+----------------+-------+--------------------+----------------+
| pets       | id          | bigint(20)  |                | NO          | PRI        |                        1 | NULL           |       | NULL               | NULL           |
| pets       | owner_id    | bigint(20)  |                | YES         | MUL        |                        0 | NULL           |       | NULL               | NULL           |
+------------+-------------+-------------+----------------+-------------+------------+--------------------------+----------------+-------+--------------------+----------------+

[a8m]

OK, just checked that on https://mariadb.com/kb/en/information-schema-columns-table/ and this patch should solve the issue. Please, add it to the mysql/inspect.go file:

 // marDefaultExpr returns the correct schema.Expr based on the column attributes for MariaDB.
 func (i *inspect) marDefaultExpr(c *schema.Column, x string) schema.Expr {
+       // Unlike MySQL, NULL means default to NULL or no default.
+       if x == "NULL" {
+               return nil
+       }
        // From MariaDB 10.2.7, string-based literals are quoted to distinguish them from expressions.
        if i.gteV("10.2.7") && sqlx.IsQuoted(x, '\'') {

[a8m]

@fishead, you're also welcome to our atlas community on Discord 😃
https://discord.com/invite/QhsmBAWzrC

[fishead]

@a8m PR updated. Thanks for the detail.

[a8m]

💯