Migration

During NocoBase plugin development and updates, plugin database structures or configurations may undergo incompatible changes. To ensure smooth upgrades, NocoBase provides a Migration mechanism to handle these changes by writing migration files. This guide will help you systematically understand Migration usage and development workflow.

Migration Concept

Migration is a script that automatically executes during plugin upgrades, used to solve the following problems:

Data table structure adjustments (adding fields, modifying field types, etc.)
Data migration (such as batch updates of field values)
Plugin configuration or internal logic updates

Migration execution timing is divided into three types:

Type	Trigger Timing	Execution Scenario
`beforeLoad`	Before all plugin configurations are loaded
`afterSync`	After collection configurations are synchronized with the database (the collection structure has already been changed)
`afterLoad`	After all plugin configurations are loaded

Create Migration Files

Migration files should be placed in src/server/migrations/*.ts in the plugin directory. NocoBase provides the create-migration command to quickly generate migration files.

bash

yarn nocobase create-migration [options] <name>

Optional Parameters

Parameter	Description
`--pkg <pkg>`	Specify plugin package name
`--on [on]`	Specify execution timing, options: `beforeLoad`, `afterSync`, `afterLoad`

Example

bash

$ yarn nocobase create-migration update-ui --pkg=@nocobase/plugin-client

Generated migration file path:

/nocobase/packages/plugins/@nocobase/plugin-client/src/server/migrations/20240107173313-update-ui.ts

File initial content:

import { Migration } from '@nocobase/server';

export default class extends Migration {
  on = 'afterLoad'; // 'beforeLoad' | 'afterSync' | 'afterLoad'
  appVersion = '<0.19.0-alpha.3';

  async up() {
    // Write upgrade logic here
  }
}

⚠️ appVersion is used to identify the version targeted by the upgrade. Environments with versions less than the specified version will execute this migration.

Writing Migration

In Migration files, you can access the following common properties and APIs through this to conveniently operate database, plugins, and application instances:

Common Properties

this.app
Current NocoBase application instance. Can be used to access global services, plugins, or configuration.
ts
```
const config = this.app.config.get('database');
```
this.db
Database service instance, provides interfaces for operating on models (Collections).
ts
```
const users = await this.db.getRepository('users').findAll();
```
this.plugin
Current plugin instance, can be used to access plugin custom methods.
ts
```
const settings = this.plugin.customMethod();
```

this.sequelize
Sequelize instance, can directly execute raw SQL or transaction operations.

await this.sequelize.transaction(async (transaction) => {
  await this.sequelize.query('UPDATE users SET active = 1', { transaction });
});

this.queryInterface
Sequelize's QueryInterface, commonly used to modify table structures, such as adding fields, deleting tables, etc.
ts
```
await this.queryInterface.addColumn('users', 'age', {
  type: this.sequelize.Sequelize.INTEGER,
  allowNull: true,
});
```

Writing Migration Example

import { Migration } from '@nocobase/server';

export default class extends Migration {
  on = 'afterSync';
  appVersion = '<0.19.0-alpha.3';

  async up() {
    // Use queryInterface to add field
    await this.queryInterface.addColumn('users', 'nickname', {
      type: this.sequelize.Sequelize.STRING,
      allowNull: true,
    });

    // Use db to access data models
    const users = await this.db.getRepository('users').findAll();
    for (const user of users) {
      user.nickname = user.username;
      await user.save();
    }

    // Execute plugin custom method
    await this.plugin.customMethod();
  }
}

In addition to the common properties listed above, Migration also provides rich APIs. For detailed documentation, see Migration API.

Trigger Migration

Migration execution is triggered by the nocobase upgrade command:

bash

$ yarn nocobase upgrade

During upgrade, the system will determine execution order based on Migration type and appVersion.

Testing Migration

In plugin development, it's recommended to use Mock Server to test whether migration executes correctly, avoiding damage to real data.

import { createMockServer, MockServer } from '@nocobase/test';

describe('Migration Test', () => {
  let app: MockServer;

  beforeEach(async () => {
    app = await createMockServer({
      plugins: ['my-plugin'], // Plugin name
      version: '0.18.0-alpha.5', // Version before upgrade
    });
  });

  afterEach(async () => {
    await app.destroy();
  });

  test('run upgrade migration', async () => {
    await app.runCommand('upgrade');
    // Write verification logic, such as checking if field exists, if data migration succeeded
  });
});

Tip: Using Mock Server can quickly simulate upgrade scenarios and verify Migration execution order and data changes.

Development Practice Recommendations

Split Migration
Try to generate one migration file per upgrade, to maintain atomicity and simplify troubleshooting.
Specify Execution Timing
Choose beforeLoad, afterSync, or afterLoad based on operation objects, avoid depending on unloaded modules.
Handle Versioning
Use appVersion to clearly specify the version applicable to the migration to prevent repeated execution.
Test Coverage
Verify the migration on a Mock Server before executing the upgrade in a real environment.