Add has_many :primary_key option

There's a good reason for doing this as opposed to setting the primary key for the class, and that's in cases where there is a generated key that is used to join two tables together.

Attached patch adds support for :primary_key option for has_one associations as well.

John Hume noted on Rails-Core that :primary_key might be confusing and suggested :alternate_key. I think just :key might suffice. Thoughts?

I think that either :key or :alternate_key would be good.

Also, I agree with Brad about monkeypatching this into AR. ActiveRecord does a poor job of making itself configurable (via runtime options) and extensible (via code to provide more features). You only have to look at ActiveRecord::Base.find to see that.

Not only does this patch add a feature that, while you may not need it, seems like something that should be a configuration option, it also abstracts the association's knowledge of how to get the quoted_id, something that is very important if one were to write a plugin to add this functionality.

As an aside, what is up with Lighthouse's spam filter? It's flagging comments that also change the state of the ticket made by the person who owns the ticket.

Other people do want this. Here is a thread from the rubyonrails list where someone wants to know how to set the key on a has_one association:

http://groups.google.com/group/r...

Without quoted_id abstracted out, a plugin would be extremely brittle, and it would probably have to be rewritten whenever the rails association code changed.

I really think this is a good option to have, since it makes associations much more flexible with very little complexity.

Can an admin please go to /spams and mark the above comments as ham?

I think it's a good idea to make AR code more extensible such that plugins like this are not very brittle.

Not sure what's up with LH.

If you'd like, I could make another patch that just abstracts out quoted_id so that I could just overwrite that in my plugin.

Are you any more inclined to include this feature since other people have been asking for it on the rails list?

I think we can abstract quoted_id to start with. And include the feature in core if more people asks for it.

Thanks.

I've attached a patch that abstracts out @owner.quoted_id to a method named owner_quoted_id. All of the tests still pass. Thanks.

Sorry for the wait.

I think the :primary_key option is great for denormalization and for legacy databases, also.

Could you rebase the :primary_key patch against latest master?

Okay, I've rebased my and Brad's patches against master, and included both patches in the attached 0001-primary-key-option.patch. Please let me know if there's anything else you need to get this applied. Thanks!

It's actually been committed now :)

I didn't resolve it earlier since the other patch is still open. indirect, could you open a new ticket and rebase against latest master?

Hi Jeremy... all the patches on this ticket have been committed. I rebased a few weeks ago for koz:

http://github.com/rails/rails/co...

Thanks for following up, though. :)

Great, thanks!

Just wanted to add some additional motivation for this patch. I'm using uuids in a multi-machine, multi-database configuration with ActiveResource. Since objects are moved between databases on each machine, they can't use the autoincrementing 'id' column, hence uuids. Changing the database primary key to be a uuid has a negative impact on Innodb performance so this patch is the right solution.

Since all sides of the association are impacted (has_many, belongs_to), the ideal solution would be to specify the primary key as an option on each association declaration, and avoid the finder_sql syntax, which doesn't work on the belongs_to anyway. Of course the same issue exists with has_and_belongs_to_many.

Logan,

I don't think any additional motivation is needed, since the patch has already been applied to rails. If there are further changes to associations that you would like to make (like adding support for belongs_to :primary_key), a patch would be great. :)

Perfect, this is just what I needed. Thanks!