Feature/primary keys

[D1plo1d]

Adding a :primary_key option to closure tree. This allows closure tree to reference models in the tree by a different column then their default primary key.

Useful when dealing with models which have both and id and a uuid and the closure tree needs to be built off the uuids.

[mceachen]

Thanks for the PR, I'll review it asap.

Out of curiosity, when would you want two unique identifiers for a table?

Or is this to support a legacy table design?

[D1plo1d]

@mceachen The uuids are generated on an ios app that synchronize their data with the server when they can. So I use accepts_nested_attributes to save the models + hierarchy data. Because I'm saving the models all at once I don't have access to a parent's id until after all the models are saved. So I used uuids w/ closure trees to reduce the number of SQL interactions I needed to save the models.

The auto increment id primary key is just to leave my options open so that I can speed up non-closure_tree lookups later on as need be (because it's less bytes per key and there will be less empty space between keys in the keyspace).

[D1plo1d]

Hmm, this seems to have broken a lot of unit tests. Unfortunately I don't have mysql on my machine. This is a bit of a problem..

[mceachen]

If you can get the tests to pass, and add a model in the tests that exercise this, I'm happy to merge it.

[D1plo1d]

I added unit tests for the primary key feature and fixed all the errors I was seeing when I ran rspec.

However when I run tests.sh I'm seeing a bunch more issues which I'm less certain about.

In particular I'm getting "time interval must be positive" from parallel_spec.rb:10:. And recursive locking errors from database_cleaner.rb:6. It doesn't seem like this is related to the changes in my pull request though and I'm not really sure of their cause.

@mceachen Thoughts?

[mceachen]

Please re-open when conflicts have been resolved and all tests pass.