function userrow_to_table(row)
  return {
     user_id = user_id,
     parent_id = user[2],
     tb_left = user[4],
     tb_right = user[5],
     children = {},
  }
end

function get_user_with_tree(user_id)
  local userrow = users.index.primary:get(user_id)
  local rootuser = userrow_to_table(userrow)
  local stack = {rootuser}
  while #stack > 0 do
    local user = table.remove(stack)
    local items = users.index.parent_id:select(user.user_id)
    for i, childrow in ipairs(items) do
      local child = userrow_to_table(childrow)
      user.children[i] = child
      table.insert(stack, child)
    end
  end
  return rootuser
end