Add bulk import functionality to Rails Active Record (add this file to config/initializers, call <model>.import!(array-of-record-hashes))

active_record.rb

class ActiveRecord::Base
  
  def self.import!(record_list)
    raise ArgumentError "record_list not an Array of Hashes" unless record_list.is_a?(Array) && record_list.all? {|rec| rec.is_a? Hash }
    return record_list if record_list.empty?

    (1..record_list.count).step(1000).each do |start|
      key_list, value_list = convert_record_list(record_list[start-1..start+999])
      sql = "INSERT INTO #{self.table_name} (#{key_list.join(", ")}) VALUES #{value_list.map {|rec| "(#{rec.join(", ")})" }.join(" ,")}"
      self.connection.insert_sql(sql)
    end
    
    return record_list
  end
  
  def self.convert_record_list(record_list)
    # Build the list of keys
    key_list = record_list.map(&:keys).flatten.map(&:to_s).uniq.sort

    value_list = record_list.map do |rec|
      list = []
      key_list.each {|key| list <<  ActiveRecord::Base.connection.quote(rec[key] || rec[key.to_sym]) }
      list
    end
    
    # If table has standard timestamps and they're not in the record list then add them to the record list
    time = ActiveRecord::Base.connection.quote(Time.now)
    for field_name in %w(created_at updated_at)
      if self.column_names.include?(field_name) && !(key_list.include?(field_name))
        key_list << field_name
        value_list.each {|rec| rec << time }
      end
    end
    
    return [key_list, value_list]
  end
end

@jackrg how might you write this if you wanted to selectively insert columns from your raw data (e.g. in a csv, say you only want column 1, 3, and 4 to save to your ActiveRecord table instead of all columns 1-4)? I know how to do that using CSV.foreach, but it's taking 5 minutes to import 20,000 rows.

This is vulnerable to sql injection - you need to escape values!