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Diffstat (limited to 'user_guide_src/source/libraries/migration.rst')
| -rw-r--r-- | user_guide_src/source/libraries/migration.rst | 134 |
1 files changed, 133 insertions, 1 deletions
diff --git a/user_guide_src/source/libraries/migration.rst b/user_guide_src/source/libraries/migration.rst index 5192f1f29..cb7d96a6d 100644 --- a/user_guide_src/source/libraries/migration.rst +++ b/user_guide_src/source/libraries/migration.rst @@ -2,4 +2,136 @@ Migrations Class ################ -Coming soon.
\ No newline at end of file +Migrations are a convenient way for you to alter your database in a +structured and organized manner. You could edit fragments of SQL by hand +but you would then be responsible for telling other developers that they +need to go and run them. You would also have to keep track of which changes +need to be run against the production machines next time you deploy. + +The database table **migration** tracks which migrations have already been +run so all you have to do is update your application files and +call **$this->migrate->current()** to work out which migrations should be run. +The current version is found in **config/migration.php**. + +****************** +Create a Migration +****************** + +.. note:: Each Migration is run in numerical order forward or backwards + depending on the method taken. Use a prefix of 3 numbers followed by an + underscore for the filename of your migration. + +This will be the first migration for a new site which has a blog. All +migrations go in the folder **application/migrations/** and have names such +as: **001_add_blog.php**.:: + + defined('BASEPATH') OR exit('No direct script access allowed'); + + class Migration_Add_blog extends CI_Migration { + + public function up() + { + $this->dbforge->add_field(array( + 'blog_id' => array( + 'type' => 'INT', + 'constraint' => 5, + 'unsigned' => TRUE, + 'auto_increment' => TRUE + ), + 'blog_title' => array( + 'type' => 'VARCHAR', + 'constraint' => '100', + ), + 'blog_description' => array( + 'type' => 'TEXT', + 'null' => TRUE, + ), + )); + + $this->dbforge->create_table('blog'); + } + + public function down() + { + $this->dbforge->drop_table('blog'); + } + +Then in **application/config/migration.php** set **$config['migration_version'] = 1;**. + +************* +Usage Example +************* + +In this example some simple code is placed in **application/controllers/migrate.php** +to update the schema.:: + + $this->load->library('migration'); + + if ( ! $this->migration->current()) + { + show_error($this->migration->error_string()); + } + +****************** +Function Reference +****************** + +There are five available methods for the Migration class: + +- $this->migration->current(); +- $this->migration->error_string(); +- $this->migration->find_migrations(); +- $this->migration->latest(); +- $this->migration->version(); + +$this->migration->current() +============================ + +The current migration is whatever is set for **$config['migration_version']** in +**application/config/migration.php**. + +$this->migration->error_string() +================================= + +This returns a string of errors while performing a migration. + +$this->migration->find_migrations() +==================================== + +An array of migration filenames are returned that are found in the **migration_path** +property. + +$this->migration->latest() +=========================== + +This works much the same way as current() but instead of looking for +the **$config['migration_version']** the Migration class will use the very +newest migration found in the filesystem. + +$this->migration->version() +============================ + +Version can be used to roll back changes or step forwards programmatically to +specific versions. It works just like current but ignores **$config['migration_version']**.:: + + $this->load->library('migration'); + + $this->migration->version(5); + +********************* +Migration Preferences +********************* + +The following is a table of all the config options for migrations. + +========================== ====================== ============= ============================================= +Preference Default Options Description +========================== ====================== ============= ============================================= +**migration_enabled** FALSE TRUE / FALSE Enable or disable migrations. +**migration_path** APPPATH.'migrations/' None The path to your migrations folder. +**migration_version** 0 None The current version your database should use. +**migration_table** migrations None The table name for storing the shema + version number. +**migration_auto_latest** FALSE TRUE / FALSE Enable or disable automatically + running migrations. +========================== ====================== ============= ============================================= |