Much faster (~x300) master data import for Rails

import.rake

def create_master model_class, &block
  return unless block_given?

  csv = "#{Rails.root}/db/masters/#{model_class.name.split('::').last.underscore}.csv"
  model_class.destroy_all
  model_class.create! CSV.open(csv).map(&block)
end

def import_master_unsafe model_class, &block
  return unless block_given?

  csv = "#{Rails.root}/db/masters/#{model_class.name.split('::').last.underscore}.csv"
  columns = block.call(CSV.open(csv).first).keys

  ActiveRecord::Base.connection.execute <<-EOF
    LOAD DATA INFILE "#{csv}" REPLACE
         INTO TABLE `#{model_class.table_name}`
         FIELDS TERMINATED BY ','
         (#{columns.join(", ")})
         SET `created_at` = '#{Time.current.to_s(:db)}', `updated_at` = '#{Time.current.to_s(:db)}';
  EOF
end

namespace :master do
  desc "Create master data"
  task import: :environment do

    puts "create ContactType"
    create_master M::ContactType do |contact_type|
      {id: contact_type[0], name: contact_type[1]}
    end

    puts "create JapanAddress"
    create_master_unsafe M::JapanAddress do |japan_address|
      { code: japan_address[0], address1: japan_address[1], address2: japan_address[2], address3: japan_address[3]}
    end
  end
end