Data Migrator

Run data migrations.

Data migrations are stored in db/data. They act like schema migrations, except they should be reserved for data migrations.

Problems this gem is solving :

Migrating data using model which has attribute not created in database

Example:

• Migration adding a new attribute to the model User.
• Migration migrating data to populate User models.
• Migration adding a new attribute to the model User.

The second migration will break because the model User now use a new attribute which will not be created in the database at this time.

Using this gem, you can now run data migrations after executing all schema migrations.

Using a staging environment using the production database

In this case when we deploy to production, we need to run again migration of the data because models in production was still not using the last schema.

Example: When adding a new attribute to the model user, while begin in staging, the production will not create the user as it does not know about it.

Using this gem, you can specify a prefix (env_prefix) for the version registered in the data versioning table. (example: 'staging' or 'production')

Ensure migration are runnable multiple times

As run migration on staging and in production, this mean migration should runnable multiple times agains the same database. You can simplify call multiple times rake db:data:migrate to verify migrations are correct.

What's it do?

Data migrations are stored in db/data. They act like schema migrations, except they should be reserved for data migrations. Running any of the provided rake tasks also creates a data schema table to mirror the usual schema migrations table to track all the goodness.

Data migrations can be created at the same time as schema migrations, or independently.

Rails 4.1 and Ruby 2.0

Data Migrator is Rails 4.1 and Ruby > 2.0 compatible.

Installation

Add the gem to your project

# Gemfile
gem 'data_migrator'

Then bundle install and you are ready to go.

So you know, when you use one of the provide rake tasks, a table called 'data_migrations' will be created in your database. This is to mirror the way the standard 'db' rake tasks work.

Usage

Generating Migrations

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

rails g data_migration add_this_to_that

Specify the a prefix to the data versioning table

DataMigrator.env_prefix = 'staging'

Rake Tasks

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