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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 using this method.
     *
     * More information on writing migrations is available here:
     * https://book.cakephp.org/migrations/4/en/migrations.html#the-change-method
     *
     * Remember to call "create()" or "update()" and NOT "save()" when working
     * with the Table class.
     *
     */
    public function change()
    {

    }
}

All migrations extend from the BaseMigration or BaseMigration. These classes provides the necessary support to create your database migrations. Database migrations can transform your database in many ways, such as creating new tables, inserting rows, adding indexes and modifying columns.

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 migrate down automatically for you. For example:

<?php

use Migrations\BaseMigration;

class CreateUserLoginsTable extends BaseMigration
{
    public function change()
    {
        // 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 automatically 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()
    {
        // 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.

Executing Queries¶

Queries can be executed with the execute() and query() methods. The execute() method returns the number of affected rows whereas the query() method returns the result as a CakePHP Statement. Both methods accept an optional second parameter $params which is an array of elements, and if used will cause the underlying connection to use a prepared statement.

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up()
    {
        // execute()
        $count = $this->execute('DELETE FROM users'); // returns the number of affected rows

        // query()
        $stmt = $this->query('SELECT * FROM users'); // returns PDOStatement
        $rows = $stmt->fetchAll(); // returns the result as an array

        // using prepared queries
        $count = $this->execute('DELETE FROM users WHERE id = ?', [5]);
        $stmt = $this->query('SELECT * FROM users WHERE id > ?', [5]); // returns PDOStatement
        $rows = $stmt->fetchAll();
    }

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

    }
}

Note

These commands run using the PHP Data Objects (PDO) extension which defines a lightweight, consistent interface for accessing databases in PHP. Always make sure your queries abide with PDOs before using the execute() command. This is especially important when using DELIMITERs during insertion of stored procedures or triggers which don’t support DELIMITERs.

Note

If you wish to execute multiple queries at once, you may not also use the prepared variant of these functions. When using prepared queries, PDO can only execute them one at a time.

Warning

When using execute() or query() with a batch of queries, PDO doesn’t throw an exception if there is an issue with one or more of the queries in the batch.

As such, the entire batch is assumed to have passed without issue.

If Migrations was to iterate any potential result sets, looking to see if one had an error, then Migrations would be denying access to all the results as there is no facility in PDO to get a previous result set nextRowset() - but no previousSet()).

So, as a consequence, due to the design decision in PDO to not throw an exception for batched queries, Migrations is unable to provide the fullest support for error handling when batches of queries are supplied.

Fortunately though, all the features of PDO are available, so multiple batches can be controlled within the migration by calling upon nextRowset() and examining errorInfo.

Fetching Rows¶

There are two methods available to fetch rows. The fetchRow() method will fetch a single row, whilst the fetchAll() method will return multiple rows. Both methods accept raw SQL as their only parameter.

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up()
    {
        // fetch a user
        $row = $this->fetchRow('SELECT * FROM users');

        // fetch an array of messages
        $rows = $this->fetchAll('SELECT * FROM messages');
    }

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

    }
}

Inserting Data¶

Migrations makes it easy to insert data into your tables. Whilst this feature is intended for the seed feature, you are also free to use the insert methods in your migrations.

<?php

use Migrations\BaseMigration;

class NewStatus extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up()
    {
        $table = $this->table('status');

        // inserting only one row
        $singleRow = [
            'id'    => 1,
            'name'  => 'In Progress'
        ];

        $table->insert($singleRow)->saveData();

        // inserting multiple rows
        $rows = [
            [
              'id'    => 2,
              'name'  => 'Stopped'
            ],
            [
              'id'    => 3,
              'name'  => 'Queued'
            ]
        ];

        $table->insert($rows)->saveData();
    }

    /**
     * Migrate Down.
     */
    public function down()
    {
        $this->execute('DELETE FROM status');
    }
}

Note

You cannot use the insert methods inside a change() method. Please use the up() and down() methods.

Working With Tables¶

The Table object is one of the most useful APIs provided by Migrations. It allows 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()
    {
        $table = $this->table('tableName');
    }

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

    }
}

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

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.

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()
    {
        $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()
    {
        $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()
    {
        $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	Description
comment	set a text comment on the table
row_format	set the table row format
engine	define table engine (defaults to ``InnoDB``)
collation	define table collation (defaults to ``utf8mb4_unicode_ci``)
signed	whether the primary key is `signed` (defaults to ``false``)
limit	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()
    {
        $table = $this->table('followers', ['signed' => false]);
        $table->addColumn('follower_id', 'integer')
              ->addColumn('created', 'timestamp', ['default' => 'CURRENT_TIMESTAMP'])
              ->create();
    }
}

The PostgreSQL adapter supports the following options:

Option	Description
comment	set a text comment on the table

To view available column types and options, see `Valid Column Types`_ for details.

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()
    {
        $exists = $this->hasTable('users');
        if ($exists) {
            // do something
        }
    }

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

    }
}

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()
    {
        $this->table('users')->drop()->save();
    }

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

    /**
     * Migrate Down.
     */
    public function down()
    {
        $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()
    {
        $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()
    {

    }
}

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()
    {
        $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()
    {

    }
}

Working With 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

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);

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 columns:

Option	Description
precision	combine with `scale` set to set decimal accuracy
scale	combine with `precision` to set decimal accuracy
signed	enable or disable the `unsigned` option (only applies to MySQL)

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:

Option	Description
identity	enable or disable automatic incrementing (if enabled, will set `null: false` if `null` option is not set)
signed	enable or disable the `unsigned` option (only applies to MySQL)

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_at and updated_at 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_at, updated_at, 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_at column will have a default set to CURRENT_TIMESTAMP. For MySQL only, update_at column will have update set to CURRENT_TIMESTAMP.

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Change.
     */
    public function change()
    {
        // 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)

For foreign key definitions:

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

You can pass one or more of these options to any column with the optional third argument array.

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();

Custom Column Types & Default Values¶

Some DBMS systems provide additional column types and default values that are specific to them. If you don’t want to keep your migrations DBMS-agnostic you can use those custom types in your migrations through the \Migrations\Db\Literal::from method, which takes a string as its only argument, and returns an instance of \Migrations\Db\Literal. When Migrations encounters this value as a column’s type it knows not to run any validation on it and to use it exactly as supplied without escaping. This also works for default values.

You can see an example below showing how to add a citext column as well as a column whose default value is a function, in PostgreSQL. This method of preventing the built-in escaping is supported in all adapters.

<?php

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

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

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()
    {
        $columns = $this->table('users')->getColumns();
        ...
    }

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

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()
    {
        $column = $this->table('users')->getColumn('email');
        ...
    }

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

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()
    {
        $table = $this->table('user');
        $column = $table->hasColumn('username');

        if ($column) {
            // do something
        }

    }
}

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()
    {
        $table = $this->table('users');
        $table->renameColumn('bio', 'biography')
              ->save();
    }

    /**
     * Migrate Down.
     */
    public function down()
    {
        $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()
    {
        $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()
    {
        $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()
    {
        $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 Working With Columns and Valid Column Options for allowed values.

<?php

use Migrations\BaseMigration;

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

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

    }
}

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()
    {
        $table = $this->table('users');
        $table->addColumn('city', 'string')
              ->addIndex(['city'])
              ->save();
    }

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

    }
}

By default Migrations instructs the database adapter to create a normal 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()
    {
        $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();
    }

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

    }
}

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()
    {
        $table = $this->table('users', ['engine' => 'MyISAM']);
        $table->addColumn('email', 'string')
              ->addIndex('email', ['type' => 'fulltext'])
              ->create();
    }
}

In addition, MySQL adapter also 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()
    {
        $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 also supports include (non-key) columns on indexes.

<?php

use Migrations\BaseMigration;

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

In addition PostgreSQL adapters also supports Generalized Inverted Index gin indexes.

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    public function change()
    {
        $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()
    {
        $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()
    {

    }
}

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()
    {
        $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()
    {

    }
}

“On delete” and “On update” actions are defined with a ‘delete’ and ‘update’ options array. 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]. Constraint name can be changed with the ‘constraint’ option.

It is also possible to pass addForeignKey() an array of columns. This allows us to establish a foreign key relationship to a table which uses a combined key.

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up()
    {
        $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();
    }

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

    }
}

We can add named foreign keys using the constraint parameter.

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up()
    {
        $table = $this->table('your_table');
        $table->addForeignKey('foreign_id', 'reference_table', ['id'],
                            ['constraint' => 'your_foreign_key_name']);
              ->save();
    }

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

    }
}

We can also easily check if a foreign key exists:

<?php

use Migrations\BaseMigration;

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

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

    }
}

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()
    {
        $table = $this->table('tag_relationships');
        $table->dropForeignKey('tag_id')->save();
    }

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

    }
}

Using the Query Builder¶

It is not uncommon to pair database structure changes with data changes. For example, you may want to migrate the data in a couple columns from the users to a newly created table. For this type of scenarios, Migrations provides access to a Query builder object, that you may use to execute complex SELECT, UPDATE, INSERT or DELETE statements.

The Query builder is provided by the cakephp/database project, and should be easy to work with as it resembles very closely plain SQL. Accesing the query builder is done by calling the getQueryBuilder(string $type) function. The string $type options are ‘select’, ‘insert’, ‘update’ and ‘delete’:

<?php

use Migrations\BaseMigration;

class MyNewMigration extends BaseMigration
{
    /**
     * Migrate Up.
     */
    public function up()
    {
        $builder = $this->getQueryBuilder('select');
        $statement = $builder->select('*')->from('users')->execute();
        var_dump($statement->fetchAll());
    }
}

Selecting Fields¶

Adding fields to the SELECT clause:

<?php
$builder->select(['id', 'title', 'body']);

// Results in SELECT id AS pk, title AS aliased_title, body ...
$builder->select(['pk' => 'id', 'aliased_title' => 'title', 'body']);

// Use a closure
$builder->select(function ($builder) {
    return ['id', 'title', 'body'];
});

Where Conditions¶

Generating conditions:

// WHERE id = 1
$builder->where(['id' => 1]);

// WHERE id > 1
$builder->where(['id >' => 1]);

As you can see you can use any operator by placing it with a space after the field name. Adding multiple conditions is easy as well:

<?php
$builder->where(['id >' => 1])->andWhere(['title' => 'My Title']);

// Equivalent to
$builder->where(['id >' => 1, 'title' => 'My title']);

// WHERE id > 1 OR title = 'My title'
$builder->where(['OR' => ['id >' => 1, 'title' => 'My title']]);

For even more complex conditions you can use closures and expression objects:

<?php
// Coditions are tied together with AND by default
$builder
    ->select('*')
    ->from('articles')
    ->where(function ($exp) {
        return $exp
            ->eq('author_id', 2)
            ->eq('published', true)
            ->notEq('spam', true)
            ->gt('view_count', 10);
    });

Which results in:

SELECT * FROM articles
WHERE
    author_id = 2
    AND published = 1
    AND spam != 1
    AND view_count > 10

Combining expressions is also possible:

<?php
$builder
    ->select('*')
    ->from('articles')
    ->where(function ($exp) {
        $orConditions = $exp->or_(['author_id' => 2])
            ->eq('author_id', 5);
        return $exp
            ->not($orConditions)
            ->lte('view_count', 10);
    });

It generates:

SELECT *
FROM articles
WHERE
    NOT (author_id = 2 OR author_id = 5)
    AND view_count <= 10

When using the expression objects you can use the following methods to create conditions:

eq() Creates an equality condition.
notEq() Create an inequality condition
like() Create a condition using the LIKE operator.
notLike() Create a negated LIKE condition.
in() Create a condition using IN.
notIn() Create a negated condition using IN.
gt() Create a > condition.
gte() Create a >= condition.
lt() Create a < condition.
lte() Create a <= condition.
isNull() Create an IS NULL condition.
isNotNull() Create a negated IS NULL condition.

Aggregates and SQL Functions¶

<?php
// Results in SELECT COUNT(*) count FROM ...
$builder->select(['count' => $builder->func()->count('*')]);

A number of commonly used functions can be created with the func() method:

sum() Calculate a sum. The arguments will be treated as literal values.
avg() Calculate an average. The arguments will be treated as literal values.
min() Calculate the min of a column. The arguments will be treated as literal values.
max() Calculate the max of a column. The arguments will be treated as literal values.
count() Calculate the count. The arguments will be treated as literal values.
concat() Concatenate two values together. The arguments are treated as bound parameters unless marked as literal.
coalesce() Coalesce values. The arguments are treated as bound parameters unless marked as literal.
dateDiff() Get the difference between two dates/times. The arguments are treated as bound parameters unless marked as literal.
now() Take either ‘time’ or ‘date’ as an argument allowing you to get either the current time, or current date.

When providing arguments for SQL functions, there are two kinds of parameters you can use, literal arguments and bound parameters. Literal parameters allow you to reference columns or other SQL literals. Bound parameters can be used to safely add user data to SQL functions. For example:

<?php
// Generates:
// SELECT CONCAT(title, ' NEW') ...;
$concat = $builder->func()->concat([
    'title' => 'literal',
    ' NEW'
]);
$query->select(['title' => $concat]);

Getting Results out of a Query¶

Once you’ve made your query, you’ll want to retrieve rows from it. There are a few ways of doing this:

<?php
// Iterate the query
foreach ($builder as $row) {
    echo $row['title'];
}

// Get the statement and fetch all results
$results = $builder->execute()->fetchAll('assoc');

Creating an Insert Query¶

Creating insert queries is also possible:

<?php
$builder = $this->getQueryBuilder('insert');
$builder
    ->insert(['first_name', 'last_name'])
    ->into('users')
    ->values(['first_name' => 'Steve', 'last_name' => 'Jobs'])
    ->values(['first_name' => 'Jon', 'last_name' => 'Snow'])
    ->execute();

For increased performance, you can use another builder object as the values for an insert query:

<?php

$namesQuery = $this->getQueryBuilder('select');
$namesQuery
    ->select(['fname', 'lname'])
    ->from('users')
    ->where(['is_active' => true]);

$builder = $this->getQueryBuilder('insert');
$st = $builder
    ->insert(['first_name', 'last_name'])
    ->into('names')
    ->values($namesQuery)
    ->execute();

var_dump($st->lastInsertId('names', 'id'));

The above code will generate:

INSERT INTO names (first_name, last_name)
    (SELECT fname, lname FROM USERS where is_active = 1)

Creating an update Query¶

Creating update queries is similar to both inserting and selecting:

<?php
$builder = $this->getQueryBuilder('update');
$builder
    ->update('users')
    ->set('fname', 'Snow')
    ->where(['fname' => 'Jon'])
    ->execute();

Creating a Delete Query¶

Finally, delete queries:

<?php
$builder = $this->getQueryBuilder('delete');
$builder
    ->delete('users')
    ->where(['accepted_gdpr' => false])
    ->execute();

Improve This Doc

Page Contents

Writing Migrations¶

Creating a New Migration¶

The Change Method¶

The Up Method¶

The Down Method¶

The Init Method¶

The Should Execute Method¶

Executing Queries¶

Fetching Rows¶

Inserting Data¶

Working With Tables¶

Saving Changes¶

Creating a Table¶

Determining Whether a Table Exists¶

Dropping a Table¶

Renaming a Table¶

Changing the Primary Key¶

Changing the Table Comment¶

Working With Columns¶

Valid Column Options¶

Limit Option and MySQL¶

Custom Column Types & Default Values¶

Get a column list¶

Get a column by name¶

Checking whether a column exists¶

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¶

Using the Query Builder¶

Selecting Fields¶

Where Conditions¶

Aggregates and SQL Functions¶

Getting Results out of a Query¶

Creating an Insert Query¶

Creating an update Query¶

Creating a Delete Query¶