rake db migrate - This can be used to migrate your production/test database using various options like up, down, step, redo, version etc. In this tutorial we will learn how all these options can be used with rake tool to migrate the database.

What is rake?

rake is basically ruby make. i.e. make tool for ruby

It has similar functionality to the make tool that you may have used on unix based systems for comopiling running some kind of script.

rake allows you to ruby particular task in the environment that you specify.

How to Install rake?

You can install rake by installing gem ‘rake’ as,

gem install rake

Above command will install the latest version of rake tool avaialable.

Various rake db migrate commands

These are the few of the operations that can be performed using Ruby Make i.e. rake tool on database. You can find more on rake on source page.

RAILS_ENV(Environment) under consideration -

Whenever you try any of the above command rake by default considers development as the database in use as you have not passed environment for consideration. You can explicitly pass the environment argument as follows,

rake RAILS_ENV=production db:migrate

The above command when executed rake will use production database to perform migration operation.

How rake db migrate decides which migrations to be run -

This question is resolved by rake using schema_migrations table in your database which maintains versions of the migrations that have been already run on your database. And whenever you try to run rake db migrate then it check the codebase and schema_migrations entries and difference helps deciding which migrations to be run from the codebase.