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migrations

the purpose of migrations is to easily apply and rollback changes to a database in a way that will sync across workspaces and developers. although not technically a module since exa.js has no internal code associated with migrations, it's included as a recommended way of handling database migrations anyway. the migrations directory could also be used with other tools, if so desired.

jmig​

the suggested migration tool and the one this documentation will focus on is jmig. the full documentation for this tool is located at https://github.com/realtux/jmig. jmig is invoked in an exa.js project via npx.

managing migrations​

migration files are created in the migrations folder using the jmig command npx jmig create <migration name>. to create a migration file like the one in the next section, you could run npx jmig create initial tables. after the migration file is filled out, the changes can be applied with npx jmig migrate. changes can be rolled back with npx jmig rollback.

sample migration file​

migrations/20240417195942-initial-tables.sql
up:
create table users (
    user_id int unsigned primary key auto_increment,
    name varchar(64) not null,
    email varchar(64) not null,
    created_at datetime not null
) character set utf8mb4 collate utf8mb4_unicode_ci;

down:
drop table users;

how to interpret​

a blank migration file will have only up: and down: in it to start. changes to a database should be placed under the up: section, then reversing those changes should be placed in the down:. in the provided example, a users table is created upon migration, and then dropped upon rollback.