I'm working through the Rails intro on
http://www.onlamp.com/pub/a/onlamp/2005/01/20/rails.html, and having a
bit of a problem with the part on page three, where you add a recipe
to the database.  My recipes table (in Postgresql) looks like this:

<pre>
              Table "public.recipes"
    Column    |          Type          | Modifiers 
--------------+------------------------+-----------
 id           | integer                | not null
 title        | character varying(255) | not null
 description  | character varying(255) | 
 date         | date                   | 
 instructions | text                   | 
Indexes:
    "recipes_pkey" PRIMARY KEY, btree (id)
</pre>

When I go to add an entry using the Rails structure, I get the following error:

> ActiveRecord::StatementInvalid in Recipe#create
>
> ERROR:  null value in column "id" violates not-null constraint
> : INSERT INTO recipes ("title", "date", "description", "instructions") VALUES('Cookies', 
> '2005-08-22', 'Good Stuff', 'I like cookeis a lot.
> Mix the ingredient, and cook them.
>
> yay!
> ')
>
> script/server:49

So, it's looking like Rails isn't properly handling the primary key
constraint on the table.  Is rails supposed to do this, or should I
ditch the primary key in the database?  I don't know much about
databases or about rails, so I'm probably missing something really
obvious.  Any ideas?