Plugin Migrations

If your schema changes over the life of your plugin, you can write a migration to keep existing installations updated with the latest schema. Craft automatically checks for new migrations whenever a plugin’s schema version number changes.

Creating Migrations

To create a new migration, open up your terminal and go to a Craft project that your plugin is installed in:

cd /path/to/project

Then run the following command to generate a new migration file for your plugin (replacing <migration_name> and <plugin-handle> with your migration name and plugin handle, respectively):

./craft migrate/create <migration_name> --plugin=<plugin-handle>

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If your Craft install is running from a Vagrant box, you will need to SSH into the box to run this command.

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Migration names must be valid PHP class names, though we recommend sticking with snake_case rather than StudlyCase as a convention.

Enter yes at the prompt, and a new migration file will be created in a migrations/ subfolder within your plugin’s source directory.

The migration file contains a class with two methods: safeUp() and safeDown(). safeUp() is where you should put the main migration code. If you want to make it possible to revert your migration, safeDown() is where the reversion code goes.

Logging

If you want to log any messages in your migration code, echo it out rather than calling Craft::info():

echo "    > some note\n";

If the migration is being run from a console request, this will ensure the message is seen by whoever is executing the migration, as the message will be output into the terminal. If it’s a web request, Craft will capture it and log it to storage/logs/ just as if you had used Craft::info().

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Your migration’s base classes, craft\db\Migration and yii\db\Migration, provide lots of handy methods for making changes to the database schema. Use these whenever possible, rather than calling Craft::$app->db->createCommand(), as they will automatically echo out a message about the command, and how long it took to execute.

Executing Migrations

To execute your plugin’s migrations, you’ll need to increase its schema version. (If you haven’t already explicitly defined your plugin’s schema version, it will be 1.0.0 by default.)

class Plugin extends \craft\base\Plugin
{
    public $schemaVersion = '1.0.1';

    // ...
}

With that in place, go to your Control Panel, and Craft will prompt you to run any pending plugin migrations. Click “Finish up” to do that.

Alternatively, you can run pending migrations from your terminal with the migrate/up command:

./craft migrate/up --plugin=<plugin-handle>

Install Migrations

Plugins can have a special “Install” migration which handles the installation and uninstallation of the plugin. Install migrations live at migrations/Install.php alongside normal migrations. They should follow this template:

<?php
namespace ns\prefix\migrations;

use craft\db\Migration;

class Install extends Migration
{
    public function safeUp()
    {
        // ...
    }

    public function safeDown()
    {
        // ...
    }
}

You can give your plugin an install migration with the migrate/create command if you pass the migration name “install”:

./craft migrate/create install --plugin=<plugin-handle>

When a plugin has an Install migration, its safeUp() method will be called when the plugin is installed, and its safeDown() method will be called when the plugin is uninstalled (invoked by craft\base\Plugin::install() and uninstall()).

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It is not a plugin’s responsibility to manage its row in the plugins database table. Craft takes care of that for you.