Database: Structure & Seeding

#Introduction

Migrations and seed files allow you to build, modify and populate database tables. They are primarily used by a plugin update file and are paired with the version history of a plugin. All classes are stored in the updates directory of a plugin. Migrations should tell a story about your database history and this story can be played both forwards and backwards to build up and tear down the tables.

#Migration structure

A migration file should define a class that extends the Winter\Storm\Database\Updates\Migration class and contains two methods: up and down. The up method is used to add new tables, columns, or indexes to your database, while the down method should simply reverse the operations performed by the up method. Within both of these methods you may use the schema builder to expressively create and modify tables. For example, let's look at a sample migration that creates a winter_blog_posts table:

<?php namespace Acme\Blog\Updates;

use Schema;
use Winter\Storm\Database\Updates\Migration;

class CreatePostsTable extends Migration
{
    public function up()
    {
        Schema::create('winter_blog_posts', function ($table)
        {
            $table->engine = 'InnoDB';
            $table->increments('id');
            $table->string('title');
            $table->string('slug')->index();
            $table->text('excerpt')->nullable();
            $table->text('content');
            $table->timestamp('published_at')->nullable();
            $table->boolean('is_published')->default(false);
            $table->timestamps();
        });
    }

    public function down()
    {
        Schema::drop('winter_blog_posts');
    }
}

#Creating tables

To create a new database table, use the create method on the Schema facade. The create method accepts two arguments. The first is the name of the table, while the second is a Closure which receives an object used to define the new table:

Schema::create('users', function ($table) {
    $table->increments('id');
});

Of course, when creating the table, you may use any of the schema builder's column methods to define the table's columns.

Checking for table / column existence

You may easily check for the existence of a table or column using the hasTable and hasColumn methods:

if (Schema::hasTable('users')) {
    //
}

if (Schema::hasColumn('users', 'email')) {
    //
}

Connection & storage engine

If you want to perform a schema operation on a database connection that is not your default connection, use the connection method:

Schema::connection('foo')->create('users', function ($table) {
    $table->increments('id');
});

To set the storage engine for a table, set the engine property on the schema builder:

Schema::create('users', function ($table) {
    $table->engine = 'InnoDB';

    $table->increments('id');
});

#Renaming / dropping tables

To rename an existing database table, use the rename method:

Schema::rename($from, $to);

To drop an existing table, you may use the drop or dropIfExists methods:

Schema::drop('users');

Schema::dropIfExists('users');

#Creating columns

To update an existing table, we will use the table method on the Schema facade. Like the create method, the table method accepts two arguments, the name of the table and a Closure that receives an object we can use to add columns to the table:

Schema::table('users', function ($table) {
    $table->string('email');
});

Available Column Types

Of course, the schema builder contains a variety of column types that you may use when building your tables:

Column modifiers

In addition to the column types listed above, there are several other column "modifiers" which you may use while adding the column. For example, to make the column "nullable", you may use the nullable method:

Schema::table('users', function ($table) {
    $table->string('email')->nullable();
});

Below is a list of all the available column modifiers. This list does not include the index modifiers:

#Modifying columns

The change method allows you to modify an existing column to a new type, or modify the column's attributes. For example, you may wish to increase the size of a string column. To see the change method in action, let's increase the size of the name column from 25 to 50:

Schema::table('users', function ($table) {
    $table->string('name', 50)->change();
});

We could also modify a column to be nullable:

Schema::table('users', function ($table) {
    $table->string('name', 50)->nullable()->change();
});

Renaming columns

To rename a column, you may use the renameColumn method on the Schema builder:

Schema::table('users', function ($table) {
    $table->renameColumn('from', 'to');
});

NOTE: Renaming columns in a table with a enum column is not currently supported.

#Dropping columns

To drop a column, use the dropColumn method on the Schema builder:

Schema::table('users', function ($table) {
    $table->dropColumn('votes');
});

You may drop multiple columns from a table by passing an array of column names to the dropColumn method:

Schema::table('users', function ($table) {
    $table->dropColumn(['votes', 'avatar', 'location']);
});

You can also use the dropColumnIfExists method on the Schema builder for a slightly safer way of handling migrations:

Schema::table('users', function ($table) {
    $table->dropColumnIfExists('single_column');
    // or
    $table->dropColumnIfExists('one_column', 'two_column');
    // or
    $table->dropColumnIfExists([
        'one_column',
        'two_column',
        'red_column',
        'blue_column',
    ]);
}

#Creating indexes

The schema builder supports several types of indexes. First, let's look at an example that specifies a column's values should be unique. To create the index, we can simply chain the unique method onto the column definition:

$table->string('email')->unique();

Alternatively, you may create the index after defining the column. For example:

$table->unique('email');

You may even pass an array of columns to an index method to create a compound index:

$table->index(['account_id', 'created_at']);

In most cases you should specify a name for the index manually as the second argument, to avoid the system automatically generating one that is too long:

$table->index(['account_id', 'created_at'], 'account_created');

Available index types

#Dropping indexes

To drop an index, you must specify the index's name. If no name was specified manually, the system will automatically generate one, simply concatenate the table name, the name of the indexed column, and the index type. Here are some examples:

#Foreign key constraints

There is also support for creating foreign key constraints, which are used to force referential integrity at the database level. For example, let's define a user_id column on the posts table that references the id column on a users table:

Schema::table('posts', function ($table) {
    $table->integer('user_id')->unsigned();

    $table->foreign('user_id')->references('id')->on('users');
});

As before, you may specify a name for the constraint manually by passing a second argument to the foreign method:

$table->foreign('user_id', 'user_foreign')
    ->references('id')
    ->on('users');

You may also specify the desired action for the "on delete" and "on update" properties of the constraint:

$table->foreign('user_id')
    ->references('id')
    ->on('users')
    ->onDelete('cascade');

To drop a foreign key, you may use the dropForeign method. Foreign key constraints use the same naming convention as indexes. So, if one is not specified manually, we will concatenate the table name and the columns in the constraint then suffix the name with "_foreign":

$table->dropForeign('posts_user_id_foreign');

#Seeder structure

Like migration files, a seeder class only contains one method by default: runand should extend the Seeder class. The run method is called when the update process is executed. Within this method, you may insert data into your database however you wish. You may use the query builder to manually insert data or you may use your model classes. In the example below, we'll create a new user using the User model inside the run method:

<?php namespace Acme\Users\Updates;

use Seeder;
use Acme\Users\Models\User;

class SeedUsersTable extends Seeder
{
    public function run()
    {
        $user = User::create([
            'email'                 => 'user@example.com',
            'login'                 => 'user',
            'password'              => 'password123',
            'password_confirmation' => 'password123',
            'first_name'            => 'Actual',
            'last_name'             => 'Person',
            'is_activated'          => true
        ]);
    }
}

Alternatively, the same can be achieved using the Db::table query builder method:

public function run()
{
    $user = Db::table('users')->insert([
        'email'                 => 'user@example.com',
        'login'                 => 'user',
        [...]
    ]);
}

#Calling additional seeders

Within the DatabaseSeeder class, you may use the call method to execute additional seed classes. Using the call method allows you to break up your database seeding into multiple files so that no single seeder class becomes overwhelmingly large. Simply pass the name of the seeder class you wish to run:

/**
 * Run the database seeds.
 *
 * @return void
 */
public function run()
{
    Model::unguard();

    $this->call('Acme\Users\Updates\UserTableSeeder');
    $this->call('Acme\Users\Updates\PostsTableSeeder');
    $this->call('Acme\Users\Updates\CommentsTableSeeder');
}