Page Contents

Writing Migrations

Writing Migrations¶

Migrations are a declarative API that helps you transform your database. Each migration is represented by a PHP class in a unique file. It is preferred that you write your migrations using the Migrations API, but raw SQL is also supported.

Creating a New Migration¶

Let’s start by creating a new migration with bake:

$ bin/cake bake migration

This will create a new migration in the format YYYYMMDDHHMMSS_my_new_migration.php, where the first 14 characters are replaced with the current timestamp down to the second.

If you have specified multiple migration paths, you will be asked to select which path to create the new migration in.

Bake will automatically creates a skeleton migration file with a single method:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Change Method.
     *
     * Write your reversible migrations in this method.
     */
    public function change(): void
    {
    }

}

The Change Method¶

Migrations supports ‘reversible migrations’. In many scenarios, you only need to define the up logic, and Migrations can figure out how to generate the rollback operations for you. For example:

<?php

use Migrations\BaseMigration;

class CreateUserLoginsTable extends BaseMigration
{
    public function change(): void
    {
        // create the table
        $table = $this->table('user_logins');
        $table->addColumn('user_id', 'integer')
              ->addColumn('created', 'datetime')
              ->create();
    }
}

When executing this migration, Migrations will create the user_logins table on the way up and automatically figure out how to drop the table on the way down. Please be aware that when a change method exists, Migrations will ignore the up and down methods. If you need to use these methods it is recommended to create a separate migration file.

Note

When creating or updating tables inside a change() method you must use the Table create() and update() methods. Migrations cannot automatically determine whether a save() call is creating a new table or modifying an existing one.

The following actions are reversible when done through the Table API in Migrations, and will be automatically reversed:

Creating a table
Renaming a table
Adding a column
Renaming a column
Adding an index
Adding a foreign key

If a command cannot be reversed then Migrations will throw an IrreversibleMigrationException when it’s migrating down. If you wish to use a command that cannot be reversed in the change function, you can use an if statement with $this->isMigratingUp() to only run things in the up or down direction. For example:

<?php

use Migrations\BaseMigration;

class CreateUserLoginsTable extends BaseMigration
{
    public function change(): void
    {
        // create the table
        $table = $this->table('user_logins');
        $table->addColumn('user_id', 'integer')
              ->addColumn('created', 'datetime')
              ->create();
        if ($this->isMigratingUp()) {
            $table->insert([['user_id' => 1, 'created' => '2020-01-19 03:14:07']])
                  ->save();
        }
    }
}

The Up Method¶

The up method is automatically run by Migrations when you are migrating up and it detects the given migration hasn’t been executed previously. You should use the up method to transform the database with your intended changes.

The Down Method¶

The down method is automatically run by Migrations when you are migrating down and it detects the given migration has been executed in the past. You should use the down method to reverse/undo the transformations described in the up method.

The Init Method¶

The init() method is run by Migrations before the migration methods if it exists. This can be used for setting common class properties that are then used within the migration methods.

The Should Execute Method¶

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

Working With Tables¶

The Table object enables you to easily manipulate database tables using PHP code. You can retrieve an instance of the Table object by calling the table() method from within your database migration:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $table = $this->table('tableName');
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {

    }
}

You can then manipulate this table using the methods provided by the Table object.

Adding Columns¶

Column types are specified as strings and can be one of:

binary
boolean
char
date
datetime
decimal
float
double
smallinteger
integer
biginteger
string
text
time
timestamp
uuid
binaryuuid
nativeuuid

In addition, the MySQL adapter supports enum, set, blob, tinyblob, mediumblob, longblob, bit and json column types (json in MySQL 5.7 and above). When providing a limit value and using binary, varbinary or blob and its subtypes, the retained column type will be based on required length (see Limit Option and MySQL for details).

With most adapters, the uuid and nativeuuid column types are aliases, however with the MySQL adapter + MariaDB, the nativeuuid type maps to a native uuid column instead of CHAR(36) like uuid does.

In addition, the Postgres adapter supports interval, json, jsonb, uuid, cidr, inet and macaddr column types (PostgreSQL 9.3 and above).

Valid Column Options¶

The following are valid column options:

For any column type:

Option	Description
limit	set maximum length for strings, also hints column types in adapters (see note below)
length	alias for `limit`
default	set default value or action
null	allow `NULL` values, defaults to `true` (setting `identity` will override default to `false`)
after	specify the column that a new column should be placed after, or use `\Migrations\Db\Adapter\MysqlAdapter::FIRST` to place the column at the start of the table (only applies to MySQL)
comment	set a text comment on the column

For decimal and float columns:

Option	Description
precision	total number of digits (e.g., 10 in `DECIMAL(10,2)`)
scale	number of digits after the decimal point (e.g., 2 in `DECIMAL(10,2)`)
signed	enable or disable the `unsigned` option (only applies to MySQL)

Note

Precision and Scale Terminology

Migrations follows the SQL standard where precision represents the total number of digits, and scale represents digits after the decimal point. For example, to create DECIMAL(10,2) (10 total digits with 2 decimal places):

$table->addColumn('price', 'decimal', [
    'precision' => 10,  // Total digits
    'scale' => 2,       // Decimal places
]);

This differs from CakePHP’s TableSchema which uses length for total digits and precision for decimal places. The migration adapter handles this conversion automatically.

For enum and set columns:

Option	Description
values	Can be a comma separated list or an array of values

For smallinteger, integer and biginteger columns:

For Postgres, when using identity, it will utilize the serial type appropriate for the integer size, so that smallinteger will give you smallserial, integer gives serial, and biginteger gives bigserial.

For timestamp columns:

Option	Description
default	set default value (use with `CURRENT_TIMESTAMP`)
update	set an action to be triggered when the row is updated (use with `CURRENT_TIMESTAMP`) (only applies to MySQL)
timezone	enable or disable the `with time zone` option for `time` and `timestamp` columns (only applies to Postgres)

You can add created and updated timestamps to a table using the addTimestamps() method. This method accepts three arguments, where the first two allow setting alternative names for the columns while the third argument allows you to enable the timezone option for the columns. The defaults for these arguments are created, updated, and false respectively. For the first and second argument, if you provide null, then the default name will be used, and if you provide false, then that column will not be created. Please note that attempting to set both to false will throw a \RuntimeException. Additionally, you can use the addTimestampsWithTimezone() method, which is an alias to addTimestamps() that will always set the third argument to true (see examples below). The created column will have a default set to CURRENT_TIMESTAMP. For MySQL only, updated column will have update set to CURRENT_TIMESTAMP:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Change.
     */
    public function change(): void
    {
        // Use defaults (without timezones)
        $table = $this->table('users')->addTimestamps()->create();
        // Use defaults (with timezones)
        $table = $this->table('users')->addTimestampsWithTimezone()->create();

        // Override the 'created' column name with 'recorded_at'.
        $table = $this->table('books')->addTimestamps('recorded_at')->create();

        // Override the 'updated' column name with 'amended_at', preserving timezones.
        // The two lines below do the same, the second one is simply cleaner.
        $table = $this->table('books')->addTimestamps(null, 'amended_at', true)->create();
        $table = $this->table('users')->addTimestampsWithTimezone(null, 'amended_at')->create();

        // Only add the created column to the table
        $table = $this->table('books')->addTimestamps(null, false);
        // Only add the updated column to the table
        $table = $this->table('users')->addTimestamps(false);
        // Note, setting both false will throw a \RuntimeError
    }
}

For boolean columns:

Option	Description
signed	enable or disable the `unsigned` option (only applies to MySQL)

For string and text columns:

Option	Description
collation	set collation that differs from table defaults (only applies to MySQL)
encoding	set character set that differs from table defaults (only applies to MySQL)

Limit Option and MySQL¶

When using the MySQL adapter, there are a couple things to consider when working with limits:

When using a string primary key or index on MySQL 5.7 or below, or the MyISAM storage engine, and the default charset of utf8mb4_unicode_ci, you must specify a limit less than or equal to 191, or use a different charset.
Additional hinting of database column type can be made for integer, text, blob, tinyblob, mediumblob, longblob columns. Using limit with one the following options will modify the column type accordingly:

Limit	Column Type
BLOB_TINY	TINYBLOB
BLOB_REGULAR	BLOB
BLOB_MEDIUM	MEDIUMBLOB
BLOB_LONG	LONGBLOB
TEXT_TINY	TINYTEXT
TEXT_REGULAR	TEXT
TEXT_MEDIUM	MEDIUMTEXT
TEXT_LONG	LONGTEXT
INT_TINY	TINYINT
INT_SMALL	SMALLINT
INT_MEDIUM	MEDIUMINT
INT_REGULAR	INT
INT_BIG	BIGINT

For binary or varbinary types, if limit is set greater than allowed 255 bytes, the type will be changed to the best matching blob type given the length:

<?php

use Migrations\Db\Adapter\MysqlAdapter;

//...

$table = $this->table('cart_items');
$table->addColumn('user_id', 'integer')
      ->addColumn('product_id', 'integer', ['limit' => MysqlAdapter::INT_BIG])
      ->addColumn('subtype_id', 'integer', ['limit' => MysqlAdapter::INT_SMALL])
      ->addColumn('quantity', 'integer', ['limit' => MysqlAdapter::INT_TINY])
      ->create();

Default values with expressions¶

If you need to set a default to an expression, you can use a Literal to have the column’s default value used without any quoting or escaping. This is helpful when you want to use a function as a default value:

use Migrations\BaseMigration;
use Migrations\Db\Literal;

class AddSomeColumns extends BaseMigration
{
    public function change(): void
    {
        $this->table('users')
              ->addColumn('uniqid', 'uuid', [
                  'default' => Literal::from('uuid_generate_v4()')
              ])
              ->create();
    }
}

Creating a Table¶

Creating a table is really easy using the Table object. Let’s create a table to store a collection of users:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    public function change(): void
    {
        $users = $this->table('users');
        $users->addColumn('username', 'string', ['limit' => 20])
              ->addColumn('password', 'string', ['limit' => 40])
              ->addColumn('password_salt', 'string', ['limit' => 40])
              ->addColumn('email', 'string', ['limit' => 100])
              ->addColumn('first_name', 'string', ['limit' => 30])
              ->addColumn('last_name', 'string', ['limit' => 30])
              ->addColumn('created', 'datetime')
              ->addColumn('updated', 'datetime', ['null' => true])
              ->addIndex(['username', 'email'], ['unique' => true])
              ->create();
    }
}

Columns are added using the addColumn() method. We create a unique index for both the username and email columns using the addIndex() method. Finally calling create() commits the changes to the database.

Note

Migrations automatically creates an auto-incrementing primary key column called id for every table.

The id option sets the name of the automatically created identity field, while the primary_key option selects the field or fields used for primary key. id will always override the primary_key option unless it’s set to false. If you don’t need a primary key set id to false without specifying a primary_key, and no primary key will be created.

To specify an alternate primary key, you can specify the primary_key option when accessing the Table object. Let’s disable the automatic id column and create a primary key using two columns instead:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    public function change(): void
    {
        $table = $this->table('followers', ['id' => false, 'primary_key' => ['user_id', 'follower_id']]);
        $table->addColumn('user_id', 'integer')
              ->addColumn('follower_id', 'integer')
              ->addColumn('created', 'datetime')
              ->create();
    }
}

Setting a single primary_key doesn’t enable the AUTO_INCREMENT option. To simply change the name of the primary key, we need to override the default id field name:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    public function up(): void
    {
        $table = $this->table('followers', ['id' => 'user_id']);
        $table->addColumn('follower_id', 'integer')
              ->addColumn('created', 'timestamp', ['default' => 'CURRENT_TIMESTAMP'])
              ->create();
    }
}

In addition, the MySQL adapter supports following options:

Option	Platform	Description
comment	MySQL, Postgres	set a text comment on the table
collation	MySQL, SqlServer	the default collation for a table if different than the database.
row_format	MySQL	set the table row format
engine	MySQL	define table engine (defaults to ``InnoDB``)
collation	MySQL	define table collation (defaults to ``utf8mb4_unicode_ci``)
signed	MySQL	whether the primary key is `signed` (defaults to ``false``)
limit	MySQL	set the maximum length for the primary key

By default, the primary key is unsigned. To simply set it to be signed just pass signed option with a true value:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    public function change(): void
    {
        $table = $this->table('followers', ['signed' => false]);
        $table->addColumn('follower_id', 'integer')
              ->addColumn('created', 'timestamp', ['default' => 'CURRENT_TIMESTAMP'])
              ->create();
    }
}

If you need to create a table with a different collation than the database, use:

<?php
use Migrations\BaseMigration;

class CreateCategoriesTable extends BaseMigration
{
    public function change(): void
    {
        $table = $this
            ->table('categories', [
                'collation' => 'latin1_german1_ci'
            ])
            ->addColumn('title', 'string')
            ->create();
    }
}

Note however this can only be done on table creation : there is currently no way of adding a column to an existing table with a different collation than the table or the database. Only MySQL and SqlServer supports this configuration key for the time being.

To view available column types and options, see Adding Columns for details.

Saving Changes¶

When working with the Table object, Migrations stores certain operations in a pending changes cache. Once you have made the changes you want to the table, you must save them. To perform this operation, Migrations provides three methods, create(), update(), and save(). create() will first create the table and then run the pending changes. update() will just run the pending changes, and should be used when the table already exists. save() is a helper function that checks first if the table exists and if it does not will run create(), else it will run update().

As stated above, when using the change() migration method, you should always use create() or update(), and never save() as otherwise migrating and rolling back may result in different states, due to save() calling create() when running migrate and then update() on rollback. When using the up()/down() methods, it is safe to use either save() or the more explicit methods.

When in doubt with working with tables, it is always recommended to call the appropriate function and commit any pending changes to the database.

Renaming a Column¶

To rename a column, access an instance of the Table object then call the renameColumn() method:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $table = $this->table('users');
        $table->renameColumn('bio', 'biography')
              ->save();
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {
        $table = $this->table('users');
        $table->renameColumn('biography', 'bio')
               ->save();
    }
}

Adding a Column After Another Column¶

When adding a column with the MySQL adapter, you can dictate its position using the after option, where its value is the name of the column to position it after:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Change Method.
     */
    public function change(): void
    {
        $table = $this->table('users');
        $table->addColumn('city', 'string', ['after' => 'email'])
              ->update();
    }
}

This would create the new column city and position it after the email column. The \Migrations\Db\Adapter\MysqlAdapter::FIRST constant can be used to specify that the new column should be created as the first column in that table.

Dropping a Column¶

To drop a column, use the removeColumn() method:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate up.
     */
    public function up(): void
    {
        $table = $this->table('users');
        $table->removeColumn('short_name')
              ->save();
    }
}

Specifying a Column Limit¶

You can limit the maximum length of a column by using the limit option:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Change Method.
     */
    public function change(): void
    {
        $table = $this->table('tags');
        $table->addColumn('short_name', 'string', ['limit' => 30])
              ->update();
    }
}

Changing Column Attributes¶

To change column type or options on an existing column, use the changeColumn() method. See valid-column-types and Valid Column Options for allowed values:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $users = $this->table('users');
        $users->changeColumn('email', 'string', ['limit' => 255])
              ->save();
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {

    }
}

Working With Indexes¶

To add an index to a table you can simply call the addIndex() method on the table object:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $table = $this->table('users');
        $table->addColumn('city', 'string')
              ->addIndex(['city'])
              ->save();
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {

    }
}

By default Migrations instructs the database adapter to create a simple index. We can pass an additional parameter unique to the addIndex() method to specify a unique index. We can also explicitly specify a name for the index using the name parameter, the index columns sort order can also be specified using the order parameter. The order parameter takes an array of column names and sort order key/value pairs:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $table = $this->table('users');
        $table->addColumn('email', 'string')
              ->addColumn('username','string')
              ->addIndex(['email', 'username'], [
                    'unique' => true,
                    'name' => 'idx_users_email',
                    'order' => ['email' => 'DESC', 'username' => 'ASC']]
              )
              ->save();
    }
}

As of 4.6.0, you can use BaseMigration::index() to get a fluent builder to define indexes:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $table = $this->table('users');
        $table->addColumn('email', 'string')
              ->addColumn('username','string')
              ->addIndex(
                  $this->index(['email', 'username'])
                      ->setType('unique')
                      ->setName('idx_users_email')
                      ->setOrder(['email' => 'DESC', 'username' => 'ASC'])
              )
              ->save();
    }
}

The MySQL adapter also supports fulltext indexes. If you are using a version before 5.6 you must ensure the table uses the MyISAM engine:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    public function change(): void
    {
        $table = $this->table('users', ['engine' => 'MyISAM']);
        $table->addColumn('email', 'string')
              ->addIndex('email', ['type' => 'fulltext'])
              ->create();
    }
}

MySQL adapter supports setting the index length defined by limit option. When you are using a multi-column index, you are able to define each column index length. The single column index can define its index length with or without defining column name in limit option:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    public function change(): void
    {
        $table = $this->table('users');
        $table->addColumn('email', 'string')
              ->addColumn('username','string')
              ->addColumn('user_guid', 'string', ['limit' => 36])
              ->addIndex(['email','username'], ['limit' => ['email' => 5, 'username' => 2]])
              ->addIndex('user_guid', ['limit' => 6])
              ->create();
    }
}

The SQL Server and PostgreSQL adapters support include (non-key) columns on indexes:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    public function change(): void
    {
        $table = $this->table('users');
        $table->addColumn('email', 'string')
              ->addColumn('firstname','string')
              ->addColumn('lastname','string')
              ->addIndex(['email'], ['include' => ['firstname', 'lastname']])
              ->create();
    }
}

PostgreSQL, SQLServer, and SQLite support partial indexes by defining where clauses for the index:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    public function change(): void
    {
        $table = $this->table('users');
        $table->addColumn('email', 'string')
              ->addColumn('is_verified','boolean')
              ->addIndex(
                  $this->index('email')
                      ->setName('user_email_verified_idx')
                      ->setType('unique')
                      ->setWhere('is_verified = true')
              )
              ->create();
    }
}

PostgreSQL can create indexes concurrently which avoids taking disruptive locks during index creation:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    public function change(): void
    {
        $table = $this->table('users');
        $table->addColumn('email', 'string')
              ->addIndex(
                  $this->index('email')
                      ->setName('user_email_unique_idx')
                      ->setType('unique')
                      ->setConcurrently(true)
              )
              ->create();
    }
}

PostgreSQL adapters also supports Generalized Inverted Index gin indexes:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    public function change(): void
    {
        $table = $this->table('users');
        $table->addColumn('address', 'string')
              ->addIndex('address', ['type' => 'gin'])
              ->create();
    }
}

Removing indexes is as easy as calling the removeIndex() method. You must call this method for each index:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $table = $this->table('users');
        $table->removeIndex(['email'])
            ->save();

        // alternatively, you can delete an index by its name, ie:
        $table->removeIndexByName('idx_users_email')
            ->save();
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {

    }
}

New in version 4.6.0: Index::setWhere(), and Index::setConcurrently() were added.

Working With Foreign Keys¶

Migrations has support for creating foreign key constraints on your database tables. Let’s add a foreign key to an example table:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $table = $this->table('tags');
        $table->addColumn('tag_name', 'string')
              ->save();

        $refTable = $this->table('tag_relationships');
        $refTable->addColumn('tag_id', 'integer', ['null' => true])
                ->addForeignKey(
                    'tag_id',
                    'tags',
                    'id',
                    ['delete'=> 'SET_NULL', 'update'=> 'NO_ACTION'],
                )
                ->save();

    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {

    }
}

The ‘delete’ and ‘update’ options allow you to define the ON UPDATE and ON DELETE behavior. Possibles values are ‘SET_NULL’, ‘NO_ACTION’, ‘CASCADE’ and ‘RESTRICT’. If ‘SET_NULL’ is used then the column must be created as nullable with the option ['null' => true].

Foreign keys can be defined with arrays of columns to build constraints between tables with composite keys:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    public function up(): void
    {
        $table = $this->table('follower_events');
        $table->addColumn('user_id', 'integer')
            ->addColumn('follower_id', 'integer')
            ->addColumn('event_id', 'integer')
            ->addForeignKey(
                ['user_id', 'follower_id'],
                'followers',
                ['user_id', 'follower_id'],
                [
                    'delete'=> 'NO_ACTION',
                    'update'=> 'NO_ACTION',
                    'constraint' => 'user_follower_id',
                ]
            )
            ->save();
    }
}

The options parameter of addForeignKey() supports the following options:

Option	Description
update	set an action to be triggered when the row is updated
delete	set an action to be triggered when the row is deleted
constraint	set a name to be used by foreign key constraint
deferrable	define deferred constraint application (postgres only)

Using the foreignKey() method provides a fluent builder to define a foreign key:

<?php

use Migrations\BaseMigration;
use Migrations\Db\Table\ForeignKey;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $table = $this->table('articles');
        $table->addForeignKey(
            $this->foreignKey()
                ->setColumns('user_id')
                ->setReferencedTable('users')
                ->setReferencedColumns('user_id')
                ->setDelete(ForeignKey::CASCADE)
                ->setName('article_user_fk')
        )
        ->save();
    }
}

New in version 4.6.0: The foreignKey method was added.

We can also easily check if a foreign key exists:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $table = $this->table('tag_relationships');
        $exists = $table->hasForeignKey('tag_id');
        if ($exists) {
            // do something
        }
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {

    }
}

Finally, to delete a foreign key, use the dropForeignKey method.

Note that like other methods in the Table class, dropForeignKey also needs save() to be called at the end in order to be executed. This allows Migrations to intelligently plan migrations when more than one table is involved:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $table = $this->table('tag_relationships');
        $table->dropForeignKey('tag_id')->save();
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {

    }
}

Determining Whether a Table Exists¶

You can determine whether or not a table exists by using the hasTable() method:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $exists = $this->hasTable('users');
        if ($exists) {
            // do something
        }
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {

    }
}

Dropping a Table¶

Tables can be dropped quite easily using the drop() method. It is a good idea to recreate the table again in the down() method.

Note that like other methods in the Table class, drop also needs save() to be called at the end in order to be executed. This allows Migrations to intelligently plan migrations when more than one table is involved:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $this->table('users')->drop()->save();
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {
        $users = $this->table('users');
        $users->addColumn('username', 'string', ['limit' => 20])
              ->addColumn('password', 'string', ['limit' => 40])
              ->addColumn('password_salt', 'string', ['limit' => 40])
              ->addColumn('email', 'string', ['limit' => 100])
              ->addColumn('first_name', 'string', ['limit' => 30])
              ->addColumn('last_name', 'string', ['limit' => 30])
              ->addColumn('created', 'datetime')
              ->addColumn('updated', 'datetime', ['null' => true])
              ->addIndex(['username', 'email'], ['unique' => true])
              ->save();
    }
}

Renaming a Table¶

To rename a table access an instance of the Table object then call the rename() method:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $table = $this->table('users');
        $table
            ->rename('legacy_users')
            ->update();
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {
        $table = $this->table('legacy_users');
        $table
            ->rename('users')
            ->update();
    }
}

Changing the Primary Key¶

To change the primary key on an existing table, use the changePrimaryKey() method. Pass in a column name or array of columns names to include in the primary key, or null to drop the primary key. Note that the mentioned columns must be added to the table, they will not be added implicitly:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $users = $this->table('users');
        $users
            ->addColumn('username', 'string', ['limit' => 20, 'null' => false])
            ->addColumn('password', 'string', ['limit' => 40])
            ->save();

        $users
            ->addColumn('new_id', 'integer', ['null' => false])
            ->changePrimaryKey(['new_id', 'username'])
            ->save();
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {

    }
}

Creating Custom Primary Keys¶

You can specify a autoId property in the Migration class and set it to false, which will turn off the automatic id column creation. You will need to manually create the column that will be used as a primary key and add it to the table declaration:

<?php
use Migrations\BaseMigration;

class CreateProductsTable extends BaseMigration
{

    public bool $autoId = false;

    public function up(): void
    {
        $table = $this->table('products');
        $table
            ->addColumn('id', 'uuid')
            ->addPrimaryKey('id')
            ->addColumn('name', 'string')
            ->addColumn('description', 'text')
            ->create();
    }
}

The above will create a CHAR(36) id column that is also the primary key.

When specifying a custom primary key on the command line, you must note it as the primary key in the id field, otherwise you may get an error regarding duplicate id fields, i.e.:

bin/cake bake migration CreateProducts id:uuid:primary name:string description:text created modified

All baked migrations and snapshot will use this new way when necessary.

Warning

Dealing with primary key can only be done on table creation operations. This is due to limitations for some database servers the plugin supports.

Changing the Table Comment¶

To change the comment on an existing table, use the changeComment() method. Pass in a string to set as the new table comment, or null to drop the existing comment:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $users = $this->table('users');
        $users
            ->addColumn('username', 'string', ['limit' => 20])
            ->addColumn('password', 'string', ['limit' => 40])
            ->save();

        $users
            ->changeComment('This is the table with users auth information, password should be encrypted')
            ->save();
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {

    }
}

Checking Columns¶

BaseMigration also provides methods for introspecting the current schema, allowing you to conditionally make changes to schema, or read data. Schema is inspected when the migration is run.

Get a column list¶

To retrieve all table columns, simply create a table object and call getColumns() method. This method will return an array of Column classes with basic info. Example below:

<?php

use Migrations\BaseMigration;

class ColumnListMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $columns = $this->table('users')->getColumns();
        ...
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {
        ...
    }
}

Get a column by name¶

To retrieve one table column, simply create a table object and call the getColumn() method. This method will return a Column class with basic info or NULL when the column doesn’t exist. Example below:

<?php

use Migrations\BaseMigration;

class ColumnListMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up(): void
    {
        $column = $this->table('users')->getColumn('email');
        ...
    }

    /**
     * Migrate Down.
     */
    public function down(): void
    {
        ...
    }
}

Checking whether a column exists¶

You can check if a table already has a certain column by using the hasColumn() method:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Change Method.
     */
    public function change(): void
    {
        $table = $this->table('user');
        $column = $table->hasColumn('username');

        if ($column) {
            // do something
        }

    }
}

Changing templates¶

See Customizing Seed and Migration templates for how to customize the templates used to generate migrations.

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Page Contents

Writing Migrations¶

Creating a New Migration¶

The Change Method¶

The Up Method¶

The Down Method¶

The Init Method¶

The Should Execute Method¶

Working With Tables¶

Adding Columns¶

Valid Column Options¶

Limit Option and MySQL¶

Default values with expressions¶

Creating a Table¶

Saving Changes¶

Renaming a Column¶

Adding a Column After Another Column¶

Dropping a Column¶

Specifying a Column Limit¶

Changing Column Attributes¶

Working With Indexes¶

Working With Foreign Keys¶

Determining Whether a Table Exists¶

Dropping a Table¶

Renaming a Table¶

Changing the Primary Key¶

Creating Custom Primary Keys¶

Changing the Table Comment¶

Checking Columns¶

Get a column list¶

Get a column by name¶

Checking whether a column exists¶

Changing templates¶