Create lots of records faster with raw SQL in RoR and PostgreSQL

Insert lots of records

 #### Mass SQL INSERT Method ####
        hash = {{a=>1,b=>2},{a=>3,b=>4},{a=>5,b=>6}}  #data to insert
        connection = ActiveRecord::Base.connection
        if connection.adapter_name.downcase == "sqlite"  #Default way to do things
          parent.transaction do
            hash.each  do |h|
              parent.children.create!(h)
            end
          end
        elsif connection.adapter_name.downcase == "postgresql"  #Faster way to do things
          last_id = Child.last.id
          columns = inserts = []
          columns = hash.first.keys
          columns.concat(["parent_id","id"])
          hash.each {|c| inserts.push("(#{c.values.concat([parent.id,last_id+=1]).join(", ")})") }
          sql = "INSERT INTO positions (#{columns.join(", ")}) VALUES #{inserts.join(", ")}".chomp
          connection.execute sql
        end