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Version: 4.5

Migrations

To use migrations we need to first install @mikro-orm/migrations package.

MikroORM has integrated support for migrations via umzug. It allows you to generate migrations with current schema differences.

By default, each migration will be all executed inside a transaction, and all of them will be wrapped in one master transaction, so if one of them fails, everything will be rolled back.

Migration class​

Migrations are classes that extend Migration abstract class:

import { Migration } from '@mikro-orm/migrations';

export class Migration20191019195930 extends Migration {

  async up(): Promise<void> {
    this.addSql('select 1 + 1');
  }

}

To support undoing those changed, you can implement the down method, which throws an error by default.

Migrations are by default wrapped in a transaction. You can override this behaviour on per migration basis by implementing the isTransactional(): boolean method.

Configuration object and driver instance are available in the Migration class context.

You can execute queries in the migration via Migration.execute() method, which will run queries in the same transaction as the rest of the migration. The Migration.addSql() method also accepts instances of knex. Knex instance can be accessed via Migration.getKnex();

Initial migration​

If you want to start using migrations, and you already have the schema generated, you can do so by creating so called initial migration:

Initial migration can be created only if there are no migrations previously generated or executed.

npx mikro-orm migration:create --initial

This will create the initial migration, containing the schema dump from schema:create command. The migration will be automatically marked as executed.

Configuration​

await MikroORM.init({
  // default values:
  migrations: {
    tableName: 'mikro_orm_migrations', // name of database table with log of executed transactions
    path: './migrations', // path to the folder with migrations
    pattern: /^[\w-]+\d+\.ts$/, // regex pattern for the migration files
    transactional: true, // wrap each migration in a transaction
    disableForeignKeys: true, // wrap statements with `set foreign_key_checks = 0` or equivalent
    allOrNothing: true, // wrap all migrations in master transaction
    dropTables: true, // allow to disable table dropping
    safe: false, // allow to disable table and column dropping
    emit: 'ts', // migration generation mode
  },
})

Using via CLI​

You can use it via CLI:

npx mikro-orm migration:create   # Create new migration with current schema diff
npx mikro-orm migration:up       # Migrate up to the latest version
npx mikro-orm migration:down     # Migrate one step down
npx mikro-orm migration:list     # List all executed migrations
npx mikro-orm migration:pending  # List all pending migrations

To create blank migration file, we can use npx mikro-orm migration:create --blank.

For migration:up and migration:down commands you can specify --from (-f), --to (-t) and --only (-o) options to run only a subset of migrations:

npx mikro-orm migration:up --from 2019101911 --to 2019102117  # the same as above
npx mikro-orm migration:up --only 2019101923                  # apply a single migration
npx mikro-orm migration:down --to 0                           # migrate down all migrations

To run TS migration files, you will need to enable useTsNode flag in your package.json.

Using the Migrator programmatically​

Or you can create a simple script where you initialize MikroORM like this:

./migrate.ts
import { MikroORM } from '@mikro-orm/core';

(async () => {
  const orm = await MikroORM.init({
    dbName: 'your-db-name',
    // ...
  });

  const migrator = orm.getMigrator();
  await migrator.createMigration(); // creates file Migration20191019195930.ts
  await migrator.up(); // runs migrations up to the latest
  await migrator.up('name'); // runs only given migration, up
  await migrator.up({ to: 'up-to-name' }); // runs migrations up to given version
  await migrator.down(); // migrates one step down
  await migrator.down('name'); // runs only given migration, down
  await migrator.down({ to: 'down-to-name' }); // runs migrations down to given version
  await migrator.down({ to: 0 }); // migrates down to the first version

  await orm.close(true);
})();

Then run this script via ts-node (or compile it to plain JS and use node):

$ ts-node migrate

Providing transaction context​

In some cases you might want to control the transaction context yourself:

await orm.em.transactional(async em => {
  await migrator.up({ transaction: em.getTransactionContext() });
});

Importing migrations statically​

If you do not want to dynamically import a folder (e.g. when bundling your code with webpack) you can import migrations directly.

import { MikroORM } from '@mikro-orm/core';
import { Migration20191019195930 } from '../migrations/Migration20191019195930.ts';

await MikroORM.init({
  migrations: {
    migrationsList: [
      {
        name: 'Migration20191019195930.ts',
        class: Migration20191019195930,
      },
    ],
  },
});

With the help of webpack's context module api we can dynamically import the migrations making it possible to import all files in a folder.

import { MikroORM } from '@mikro-orm/core';
import { basename } from 'path';

const migrations = {};

function importAll(r) {
  r.keys().forEach(
    (key) => (migrations[basename(key)] = Object.values(r(key))[0])
  );
}

importAll(require.context('../migrations', false, /\.ts$/));

const migrationsList = Object.keys(migrations).map((migrationName) => ({
  name: migrationName,
  class: migrations[migrationName],
}));

await MikroORM.init({
  migrations: {
    migrationsList,
  },
});

Limitations​

MySQL​

There is no way to rollback DDL changes in MySQL. An implicit commit is forced for those queries automatically, so transactions are not working as expected.