[ruby-on-rails] Purge or recreate a Ruby on Rails database

I have a dev Ruby on Rails database full of data. I want to delete everything and rebuild the database. I'm thinking of using something like:

rake db:recreate

Is this possible?

I've today made quite a few changes to my rails schema. I realised I needed an additional two models in a hierarchy and some others to be deleted. There were many little changes required to the models and controllers.

I added the two new models and created them, using:

rake db:migrate

Then I edited the schema.rb file. I manually removed the old models that were no longer required, changed the foreign key field as required and just reordered it a bit to make it clearer to me. I deleted all the migrations, and then re-ran the build via:

rake db:reset

It worked perfectly. All the data has to be reloaded, of course. Rails realised the migrations had been deleted and reset the high-water mark:

-- assume_migrated_upto_version(20121026094813, ["/Users/sean/rails/f4/db/migrate"])

From the command line run

rake db:migrate:reset

I use:

• rails db:drop to delete the databases.
• rails db:create to create the databases based on config/database.yml

The previous commands may be replaced with rails db:reset.

Don't forget to run rails db:migrate to run the migrations.

Use like

rake db:drop db:create db:migrate db:seed

All in one line. This is faster since the environment doesn't get reloaded again and again.

db:drop - will drop database.

db:create - will create database (host/db/password will be taken from config/database.yml)

db:migrate - will run existing migrations from directory (db/migration/.rb)*.

db:seed - will run seed data possible from directory (db/migration/seed.rb)..

I usually prefer:

rake db:reset

to do all at once.

Cheers!

You can manually do:

rake db:drop
rake db:create
rake db:migrate

Or just rake db:reset, which will run the above steps but will also run your db/seeds.rb file.

An added nuance is that rake db:reset loads directly from your schema.rb file as opposed to running all the migrations files again.

You data gets blown away in all cases.

Update: In Rails 5, this command will be accessible through this command:

rails db:purge db:create db:migrate RAILS_ENV=test

As of the newest rails 4.2 release you can now run:

rake db:purge 

Source: commit

# desc "Empty the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:drop:all to drop all databases in the config). Without RAILS_ENV it defaults to purging the development and test databases."
  task :purge => [:load_config] do
    ActiveRecord::Tasks::DatabaseTasks.purge_current
  end

It can be used together like mentioned above:

rake db:purge db:create db:migrate RAILS_ENV=test

On rails 4.2, to remove all data but preserve the database

$ bin/rake db:purge && bin/rake db:schema:load

https://github.com/rails/rails/blob/4-2-stable/activerecord/CHANGELOG.md

You can use db:reset - for run db:drop and db:setup or db:migrate:reset - which runs db:drop, db:create and db:migrate.

dependent at you want to use exist schema.rb

3 options, same result:

1. All steps:

  $ rake db:drop           # deletes the database for the current env
  $ rake db:create         # creates the database for the current env
  $ rake db:schema:load    # loads the schema already generated from schema.rb / erases data
  $ rake db:seed           # seed with initial data

2. Reset:

  $ rake db:reset          # drop / schema:load / seed

3. Migrate:reset:

  $ rake db:migrate:reset  # drop / create / migrate
  $ rake db:seed

Notes:

• If schema:load is used is faster than doing all migrations, but same result.
• All data will be lost.
• You can run multiple rakes in one line.
• Works with rails 3.

In Rails 6 there is a convenient way for resetting DB and planting seeds again:

rails db:seed:replant # Truncates tables of each database for current environment and loads the seeds

https://weblog.rubyonrails.org/2019/3/15/this-week-in-rails-security-fixes-bulk-insert-and-upsert-seeds-replanting/

Because in development , you will always want to recreate the database,you can define a rake task in your lib/tasks folder like that.

  namespace :db do
      task :all => [:environment, :drop, :create, :migrate] do
   end 
end

and in terminal you will run

rake db:all

it will rebuild your database

Depending on what you're wanting, you can use…

rake db:create

…to build the database from scratch from config/database.yml, or…

rake db:schema:load

…to build the database from scratch from your schema.rb file.

According to Rails guide, this one liner should be used because it would load from the schema.rb instead of reloading the migration files one by one:

rake db:reset

I think the best way to run this command:

**rake db:reset** it does db:drop, db:setup
 rake db:setup does db:create, db:schema:load, db:seed

You can use this following command line:

rake db:drop db:create db:migrate db:seed db:test:clone

On Rails 4, all needed is

$ rake db:schema:load

That would delete the entire contents on your DB and recreate the schema from your schema.rb file, without having to apply all migrations one by one.

To drop a particular database, you can do this on rails console:

$rails console
Loading development environment
1.9.3 > ActiveRecord::Migration.drop_table(:<table_name>)
1.9.3 > exit

And then migrate DB again

$bundle exec rake db:migrate 

I use the following one liner in Terminal.

$ rake db:drop && rake db:create && rake db:migrate && rake db:schema:dump && rake db:test:prepare

I put this as a shell alias and named it remigrate

By now, you can easily "chain" Rails tasks:

$ rake db:drop db:create db:migrate db:schema:dump db:test:prepare # db:test:prepare no longer available since Rails 4.1.0.rc1+

Just issue the sequence of the steps: drop the database, then re-create it again, migrate data, and if you have seeds, sow the database:

rake db:drop db:create db:migrate db:seed

Since the default environment for rake is development, in case if you see the exception in spec tests, you should re-create db for the test environment as follows:

RAILS_ENV=test rake db:drop db:create db:migrate

In most cases the test database is being sowed during the test procedures, so db:seed task action isn't required to be passed. Otherwise, you shall to prepare the database:

rake db:test:prepare

or

RAILS_ENV=test rake db:seed

Additionally, to use the recreate task you can add into Rakefile the following code:

namespace :db do
   task :recreate => [ :drop, :create, :migrate ] do
      if ENV[ 'RAILS_ENV' ] !~ /test|cucumber/
         Rake::Task[ 'db:seed' ].invoke
      end
   end
end

Then issue:

rake db:recreate

Simply you can run

rake db:setup

It will drop database, create new database and populate db from seed if you created seed file with some data.