Rake Task for truncating all tables in a rails app. Preserves the schema_migrations.

truncate_db_task.rb

  desc "Truncate all tables in the database"
  task :truncate_all_tables! => :environment do
    unless Rails.env.production?
      puts "TRUNCATING ALL TABLES in 3 seconds!!!!"
      sleep 3
      ActiveRecord::Base.connection.tables.each do |table|
        unless table == "schema_migrations"
          puts "Truncating #{table}."
          ActiveRecord::Base.connection.execute("TRUNCATE TABLE #{table} RESTART IDENTITY CASCADE;")
        else
          puts "skipping schema_migrations table"
        end
      end
    else
      puts "This task is not available in production!!!! It will destroy all data in the database."
    end
  end

I altered the guts for later versions of rails and MySQL as follows (I use this in test_helper):

def truncate_all_tables!
    connection = ActiveRecord::Base.connection
    connection.execute 'SET FOREIGN_KEY_CHECKS = 0'
    connection.tables.each do |table|
      if %w[ar_internal_metadata schema_migrations].include? table
        puts "skipping #{table} table"
      else
        puts "Truncating #{table}."
        connection.execute("TRUNCATE TABLE #{table}")
        connection.execute("ALTER TABLE #{table} AUTO_INCREMENT = 1")
      end
    end
    connection.execute 'SET FOREIGN_KEY_CHECKS = 1'
  end

If using Database Cleaner. Also this approach does not yield Environment data not found in the schema. To resolve this issue, run: error when running db:seed:replant after.

# lib/tasks/truncate_and_reset.rake
desc "Truncate all tables in the database and reset their primary indexes"
task :truncate_and_reset => :environment do
  return "Cannot run in production as all tables will be truncated!" if Rails.env.production?
  
  require 'database_cleaner/active_record'

  DatabaseCleaner.strategy = :truncation

  DatabaseCleaner.clean
  
  puts 'All tables truncated and primary indexes reset'
end