15.3 Migration ¶

Migrations provide a way to do complicated modification of tables in a database by GNU Artanis. Here’s an example.

First, draw a migration:

# art draw migration person
drawing migration person
working Migration `20151107040209_person.scm'

You’ll see something similar like above.

Then you’d edit the file db/migration/20151107040209_person.scm:

(migrate-up
 (create-table
 'person
 '(id auto (#:primary-key))
 '(name char-field (#:not-null #:maxlen 10))
 '(age tiny-integer (#:not-null))
 '(email char-field (#:maxlen 20))))
(migrate-down
 (drop-table 'person))

Then you run the up command for migration:

art migrate up person

Then migrate-up function will be called, and this will create a table named person:

+-------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------------------+------+-----+---------+----------------+
| id | bigint(20) unsigned | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| age | tinyint(4) | NO | | NULL | |
| email | varchar(20) | YES | | NULL | |
+-------+---------------------+------+-----+---------+----------------+

If you run the down command of migration, as:

art migrate down person

The table person will be dropped.