How to delete all data from all tables in Rails?

Question

I can do Post.delete_all to delete all my posts, but what if I want to delete all posts, comments, blogs, etc.?

How do I iterate over all my models and

Answer 1

A faster way to just delete table rows is to use the TRUNCATE command.

Many of the other answers seem to ignore the difference between deleting rows and dropping a table. Dropping a table destroys the table data and schema; meaning that you need extra steps to recreate the tables. Sean McLeary's answer was the best I saw, so I used it as a starting point. However, I think it is better to take advantage of the TRUNCATE command, because it should be faster and it also resets auto-increment keys. Also, using map instead of each shortens the code a bit.

namespace :db do
  desc "Truncate all tables"
  task :truncate => :environment do
    conn = ActiveRecord::Base.connection
    tables = conn.execute("show tables").map { |r| r[0] }
    tables.delete "schema_migrations"
    tables.each { |t| conn.execute("TRUNCATE #{t}") }
  end
end

Answer 2

This will work also for Rails 4

(ActiveRecord::Base.connection.tables - ['schema_migrations']).each do |table|
    table.classify.constantize.destroy_all
end

Answer 3

I know this is an old question, but I thought this might be helpful to someone. This is a very fast way of cleaning out all data from a database.

tables = []
ActiveRecord::Base.connection.execute("show tables").each { |r| tables << r[0] }
tables = tables - ["schema_migrations"]
tables.each do |table|
  ActiveRecord::Base.connection.execute("DELETE FROM #{table} WHERE 1 = 1")
end

I use this technique in certain specs in an after(:all) block. This is much faster and more efficient than any of the Rails rake tasks for purging, migrating, reseting the database.

BTW: I'm pretty sure this would likely fail if you were enforcing foreign key constraints on the database side.

Answer 4

We have been remiss here at Stack Overflow for not mentioning the database_cleaner gem:

Database Cleaner is a set of strategies for cleaning your database in Ruby. The original use case was to ensure a clean state during tests. Each strategy is a small amount of code but is code that is usually needed in any ruby app that is testing with a database.

By 'strategy', Mr. Mabey means: truncation, transaction, and deletion.

ActiveRecord, DataMapper, Sequel, MongoMapper, Mongoid, and CouchPotato are supported.

Here is a quick code snippet from the Database Cleaner README:

require 'database_cleaner'
DatabaseCleaner.strategy = :truncation

# then, whenever you need to clean the DB
DatabaseCleaner.clean

Answer 5

Building up on @Vlad Zloteanu's answer, here is a version to remove all tables while keeping the user records and login sessions together with some meta information. Feel free to adjust the list of tables to your requirements.

# lib/tasks/db/truncate.rake

namespace :db do
  desc 'Truncate all tables except users state and meta'
  task truncate: :environment do
    conn = ActiveRecord::Base.connection
    tables = conn.tables - %w[
      sessions
      users
      roles
      users_roles
      schema_migrations
      ar_internal_metadata
    ]
    tables.each { |t| conn.execute("TRUNCATE #{t}") }

    puts "Truncated tables\n================\n#{tables.sort.join("\n")}"
  end
end

Answer 6

If you're trying to do this from code instead of the command line, say from a Test::Unit::TestCase#teardown method, you could do either

class MyTest < Test::Unit::TestCase

  def teardown
    ActiveRecord::Base.subclasses.each(&:delete_all)
  end

end

or

class MyTest < Test::Unit::TestCase

  def teardown
    Rake::Task['db:reset'].invoke
  end

end

I warn you, though: neither is particularly fast. You're definitely better off with transactional tests if you can.