Merge pull request #771 from cakephp/4.next

4.next merge to 4.x

docs/en/seeding.rst

@@ -0,0 +1,229 @@
+Database Seeding
+================
+
+Seed classes are a great way to easily fill your database with data after
+it's created. By default they are stored in the `seeds` directory; however, this
+path can be changed in your configuration file.
+
+.. note::
+
+    Database seeding is entirely optional, and Migrations does not create a `Seeds`
+    directory by default.
+
+Creating a New Seed Class
+-------------------------
+
+Migrations includes a command to easily generate a new seed class:
+
+.. code-block:: bash
+
+        $ bin/cake bake seed MyNewSeeder
+
+It is based on a skeleton template:
+
+.. code-block:: php
+
+        <?php
+
+        use Migrations\BaseSeed;
+
+        class MyNewSeeder extends BaseSeed
+        {
+            /**
+             * Run Method.
+             *
+             * Write your database seeder using this method.
+             *
+             * More information on writing seeders is available here:
+             * https://book.cakephp.org/migrations/5/en/seeding.html
+             */
+            public function run() : void
+            {
+
+            }
+        }
+
+The AbstractSeed Class
+----------------------
+
+All Migrations seeds extend from the ``BaseSeed`` or ``AbstractSeed`` classes.
+These classes provide 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.
+
+.. note::
+
+    Unlike with migrations, seeds do not keep track of which seed classes have
+    been run. This means database seeders can be run repeatedly. Keep this in
+    mind when developing them.
+
+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 seeders 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 seeders to run before the
+current seeder:
+
+.. code-block:: php
+
+        <?php
+
+        use Migrations\BaseSeed;
+
+        class ShoppingCartSeeder extends BaseSeed
+        {
+            public function getDependencies()
+            {
+                return [
+                    'UserSeeder',
+                    'ShopItemSeeder'
+                ];
+            }
+
+            public function run() : void
+            {
+                // Seed the shopping cart  after the `UserSeeder` and
+                // `ShopItemSeeder` have been run.
+            }
+        }
+
+.. note::
+
+    Dependencies are only considered when executing all seed classes (default behavior).
+    They won't be considered when running specific seed classes.
+
+Inserting Data
+--------------
+
+Using The Table Object
+~~~~~~~~~~~~~~~~~~~~~~
+
+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:
+
+.. code-block:: php
+
+        <?php
+
+        use Migrations\BaseSeed;
+
+        class PostsSeeder 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();
+            }
+        }
+
+.. note::
+
+    You must call the ``saveData()`` method to commit your data to the table.
+    Migrations will buffer data until you do so.
+
+Truncating Tables
+-----------------
+
+In addition to inserting data Migrations makes it trivial to empty your tables using the
+SQL `TRUNCATE` command:
+
+.. code-block:: php
+
+        <?php
+
+        use Migrations\BaseSeed;
+
+        class UserSeeder 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();
+            }
+        }
+
+.. note::
+
+    SQLite doesn't natively support the ``TRUNCATE`` command so behind the scenes
+    ``DELETE FROM`` is used. It is recommended to call the ``VACUUM`` command
+    after truncating a table. Migrations does not do this automatically.
+
+Executing Seed Classes
+----------------------
+
+This is the easy part. To seed your database, simply use the ``migrations seed`` command:
+
+.. code-block:: bash
+
+        $ 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:
+
+.. code-block:: bash
+
+        $ bin/cake migrations seed --seed UserSeeder
+
+You can also run multiple seeders:
+
+.. code-block:: bash
+
+        $ bin/cake migrations seed --seed UserSeeder --seed PermissionSeeder --seed LogSeeder
+
+You can also use the `-v` parameter for more output verbosity:
+
+.. code-block:: bash
+
+        $ 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.