Data Migrate
====

Run data migrations alongside schema migrations.

Data migrations are stored in db/data. They act like schema migrations, except they should be reserved for data migrations. For instance, if you realize you need to titleize all yours titles, this is the place to do it.

Data migrations can be created at the same time as schema migrations, or independently.  Database (db:) tasks have been added and extended to run on data migrations only, or in conjunction with the schema migration.  For instance, `rake db:migrate:with_data` will run both schema and data migrations in the proper order.

Note: If a data and schema migration share the same version number, schema gets precedence when migrating up. Data does down.

Rails 3 and Ruby 1.9
--------------------

Data Migrate is Rails 3.0.0 - 3.0.7,  and Ruby 1.9 compatible

Installation
------------
After adding Data Migrate to your project,

    rails g data_migrate:install
    rake db:migrate

A table 'data_migrations' table will be generated.

Usage
-----

### Generating Migrations

You can generate a data migration as you would a schema migration:

    rails g data_migration add_this_to_that

By default, the migration also generates a schema migration by the same name.
This allows you to do things like:

    rails g data_migration add_this_to_that this:string

If you need a data only migration, either run it as such, with the skip-schema-migration flag:

    rails g data_migration add_this_to_that --skip-schema-migration


### Rake Tasks

    $> rake -T data
    rake data:forward                 # Pushes the schema to the next version (specify steps w/ STEP=n).
    rake data:migrate:down            # Runs the "down" for a given migration VERSION.
    rake data:migrate:redo            # Rollbacks the database one migration and re migrate up (options: STEP=x, VERSION=x).
    rake data:migrate:status          # Display status of data migrations
    rake data:migrate:up              # Runs the "up" for a given migration VERSION.
    rake data:rollback                # Rolls the schema back to the previous version (specify steps w/ STEP=n).
    rake data:version                 # Retrieves the current schema version number for data migrations
    rake db:forward:with_data         # Pushes the schema to the next version (specify steps w/ STEP=n).
    rake db:migrate:data              # Migrate the database through scripts in db/data/migrate.
    rake db:migrate:down:with_data    # Runs the "down" for a given migration VERSION.
    rake db:migrate:redo:with_data    # Rollbacks the database one migration and re migrate up (options: STEP=x, VERSION=x).
    rake db:migrate:status:with_data  # Display status of data and schema migrations
    rake db:migrate:up:with_data      # Runs the "up" for a given migration VERSION.
    rake db:migrate:with_data         # Migrate the database data and schema (options: VERSION=x, VERBOSE=false).
    rake db:rollback:with_data        # Rolls the schema back to the previous version (specify steps w/ STEP=n).
    rake db:version:with_data         # Retrieves the current schema version numbers for data and schema migrations `

Tasks work as they would with the 'vanilla' db version.  The 'with_data' addition to the 'db' tasks will run the task in the context of both the data and schema migrations.  That is, `rake db:rollback:with_data` will check to see if it was a schema or data migration invoked last, and do that.  Tasks invoked in that space also have an additional line of output, indicating if the action is performed on data or schema.

With 'up' and 'down', you can specify the option 'BOTH', which defaults to false. Using true, will migrate both the data and schema (in the desired direction) if they both match the version provided.  Again, going up, schema is given precedence. Down its data.

For more example, assume you have the 2 files:
  db/migrate/20110419021211_add_x_to_y.rb
  db/data/20110419021211_add_x_to_y.rb

Running `rake db:migrate:up:with_data VERSION=20110419021211` would execute the 'db/migrate' version.
Running `rake db:migrate:up:with_data VERSION=20110419021211` would execute the 'db/migrate' version, followed by the 'db/data' version.

Going down instead of up would be the opposite.

`rake db:migrate:status:with_data` provides and additional column to indicate which type of migration.