Can't assign id, "Column 'id' cannot be null" - sql

Question

I inherited a database using Rails that doesn't set id incrementally, and also has two primary keys:
CREATE TABLE `t_user_history` (
`id` int(11) NOT NULL,
`history_no` int(11) NOT NULL,
`user_login_id` varchar(10) COLLATE utf8_unicode_ci NOT NULL,
`user_name` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`user_pass` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`created_at` datetime DEFAULT NULL,
`updated_at` datetime DEFAULT NULL,
`deleted_at` datetime DEFAULT NULL,
`app_version` varchar(31) COLLATE utf8_unicode_ci DEFAULT NULL,
PRIMARY KEY (`history_no`,`id`))
However, when I try to insert into this table using ruby as such:
tuser = TUserHistory.find_by_id(user.id)
TUserHistory.transaction do
ntuser = TUserHistory.new
ntuser.id = tuser.id
ntuser.history_no = 0
ntuser.user_login_id = tuser.user_login_id
ntuser.user_name = tuser.user_name
ntuser.user_pass = tuser.user_pass
ntuser.app_version = params[:app]
ntuser.save
I get the error:
getName {"error_code":"Mysql2::Error: Column 'id' cannot be null: INSERT INTO `t_user_history`
(`app_version`, `created_at`, `deleted_at`, `history_no`, `id`, `updated_at`, `user_login_id`, `user_name`, `user_pass`)
VALUES ('v1.2.9', '2012-08-30 09:26:57', NULL, 0, NULL, '2012-08-30 09:26:57', 'userlogin', 'username', 'userpass')"}
Even if I set ntuser.id = 9127 or some other value, it still says that 'id' cannot be null.
I looked at other answers that say it is indeed possible to modify this value, but it seems as though whatever value I attempt to set for ntuser.id gets ignored.
Trashing the table and starting again in a sane manner is not allowed, as this table is already being used by our services. I thought I'd create a new column for user_id, before I found out it didn't auto-increment, but even before getting to that step nothing, not even ntuser.id = 0 or deleting the line that defines ntuser.id, works.
What is going on here? Why isn't it recognizing the data is has been passed? What is the best (no, fastest) way to fix this?
Edit: Rails version 3.1.0
TUserHistory class:
class TUserHistory < ActiveRecord::Base
set_table_name "t_user_history"
default_scope select("id, user_login_id,user_name,user_pass,app_version")
acts_as_paranoid
end

Answer 1

Finally got around to doing it, by just doing an SQL statement. I wanted to use rails, seeing as how rails/ruby have wrappers for SQL code, but it just wasn't working. In the end, it looks like:
tuser = TUserHistory.order("history_no DESC").find_by_id(user.id) #get last entry
TUserHistory.transaction do
id = tuser.id
history_no = Integer(tuser.history_no)
intHist_no = history_no + 1 #because this column doesn't auto-increment
user_login_id = tuser.user_login_id
user_name = tuser.user_name
user_pass = tuser.user_pass
app_version = params[:app]
sql = "INSERT INTO t_user_history (id, history_no, user_login_id,user_name,user_pass,app_version) VALUES ('#{id}','#{intHist_no}','#{user_login_id}','#{user_name}','#{user_pass}','#{app_version}')"
ActiveRecord::Base.connection.execute(sql)
The only other thing that changed is that the class description for TUserHistory had history_no added so that it would return with the tuser select call, and could then be modified.