Database Seeding¶

Creating a New Seed Class¶

Migrations includes a command to easily generate a new seed class:

$ bin/cake bake seed MyNewSeed

It is based on a skeleton template:

<?php

use Migrations\BaseSeed;

class MyNewSeed extends BaseSeed
{
    /**
     * Run Method.
     *
     * Write your database seed using this method.
     *
     * More information on writing seeds is available here:
     * https://book.cakephp.org/migrations/5/en/seeding.html
     */
    public function run() : void
    {

    }
}

By default, the table the seed will try to alter is the “tableized” version of the seed filename.

By default, it will export all the rows found in your table. You can limit the number of rows exported by using the --limit option:

# Will only export the first 10 rows found
bin/cake bake seed --data --limit 10 Articles

If you only want to include a selection of fields from the table in your seed file, you can use the --fields option. It takes the list of fields to include as a comma separated value string:

# Will only export the fields `id`, `title` and `excerpt`
bin/cake bake seed --data --fields id,title,excerpt Articles

The BaseSeed Class¶

All Migrations seeds extend from the BaseSeed class. It provides the necessary support to create your seed classes. Seed classes are primarily used to insert test data.

The Run Method¶

The run method is automatically invoked by Migrations when you execute the cake migration seed command. You should use this method to insert your test data.

The Init Method¶

The init() method is run by Migrations before the run method if it exists. This can be used to initialize properties of the Seed class before using run.

The Should Execute Method¶

The shouldExecute() method is run by Migrations before executing the seed. This can be used to prevent the seed from being executed at this time. It always returns true by default. You can override it in your custom BaseSeed implementation.

Foreign Key Dependencies¶

Often you’ll find that seeds need to run in a particular order, so they don’t violate foreign key constraints. To define this order, you can implement the getDependencies() method that returns an array of seeds to run before the current seed:

<?php

use Migrations\BaseSeed;

class ShoppingCartSeed extends BaseSeed
{
    public function getDependencies(): array
    {
        return [
            'UserSeed',
            'ShopItemSeed'
        ];
    }

    public function run() : void
    {
        // Seed the shopping cart  after the `UserSeed` and
        // `ShopItemSeed` have been run.
    }
}

Calling a Seed from another Seed¶

Usually when seeding, the order in which to insert the data must be respected to not encounter constraint violations. Since seeds are executed in an alphabetical order by default, you can use the \Migrations\BaseSeed::call() method to define your own sequence of seeds execution:

<?php

use Migrations\BaseSeed;

class DatabaseSeed extends BaseSeed
{
    public function run(): void
    {
        $this->call('AnotherSeed');
        $this->call('YetAnotherSeed');

        // You can use the plugin dot syntax to call seeds from a plugin
        $this->call('PluginName.FromPluginSeed');
    }
}

Inserting Data¶

Seed classes can also use the familiar Table object to insert data. You can retrieve an instance of the Table object by calling the table() method from within your seed class and then use the insert() method to insert data:

<?php

use Migrations\BaseSeed;

class PostsSeed extends BaseSeed
{
    public function run() : void
    {
        $data = [
            [
                'body'    => 'foo',
                'created' => date('Y-m-d H:i:s'),
            ],[
                'body'    => 'bar',
                'created' => date('Y-m-d H:i:s'),
            ]
        ];

        $posts = $this->table('posts');
        $posts->insert($data)
              ->saveData();
    }
}

Truncating Tables¶

In addition to inserting data Migrations makes it trivial to empty your tables using the SQL TRUNCATE command:

<?php

use Migrations\BaseSeed;

class UserSeed extends BaseSeed
{
    public function run() : void
    {
        $data = [
            [
                'body'    => 'foo',
                'created' => date('Y-m-d H:i:s'),
            ],
            [
                'body'    => 'bar',
                'created' => date('Y-m-d H:i:s'),
            ]
        ];

        $posts = $this->table('posts');
        $posts->insert($data)
              ->saveData();

        // empty the table
        $posts->truncate();
    }
}

Executing Seed Classes¶

This is the easy part. To seed your database, simply use the migrations seed command:

$ bin/cake migrations seed

By default, Migrations will execute all available seed classes. If you would like to run a specific class, simply pass in the name of it using the --seed parameter:

$ bin/cake migrations seed --seed UserSeed

You can also run multiple seeds:

$ bin/cake migrations seed --seed UserSeed --seed PermissionSeed --seed LogSeed

You can also use the -v parameter for more output verbosity:

$ bin/cake migrations seed -v

The Migrations seed functionality provides a simple mechanism to easily and repeatably insert test data into your database, this is great for development environment sample data or getting state for demos.