Change id from autoincrement to char 36 in CakePHP

Question

I have web application built on CakePHP 1.2.11. and mysql database. In this application I have two tables, namely, users and actions. Users hasMany actions and the user_id (id in users tables) is the foreign key in actions table. The id field is autoincrement integer.

CakePHP documentation said that setting the id field to be Char(36) will make CakePHP able to generate Unique string for each record to be the id.

My application is running and I don't want to loss the data records that my application already has. I need to know if it is safely possible to migrate from autoincrement integer id to char(36) keeping in mind the related table?

In other word, How could I change integer value to the unique string id that cakephp do? Is there any rules? If there any tool automate this kind of migration, I will be appreciated to know it.

Answer 1

Yes, simply alter the table to use a varchar. An INT column can be translated into a char, so you won't lose the original IDs (you will end up with a mix of both old regular ints and new uuids). You will need to make sure the change is also made to any foreign keys on any other tables that will need to store VARCHAR(36) as well.

Then make sure to push the new code live immediately otherwise the new records will not be able to be created, because a varchar field can't be auto-increment.

Lastly, immediately after pushing the new code, clear your model cache so Cake doesn't still think it's an INT.

Answer 2

Are you sure you want to switch?

Honestly, unless you have a really good reason to change to UUIDs (CHAR(36)), then I would recommend just staying with auto-incrementing IDs. There are plenty of people that tout the benefits of each, but it boils down to auto-incrementing IDs can be faster, and unless you have multiple databases where you're worried about overlapping data, auto-ids are just fine. (And it's not a simple "switch")

Not crazy-simple:

If you still are sure you want to switch to UUIDs, there is no automated process, but be careful - it's not just about switching the field types and voila - you'll have to create a script or something to update the id fields as well as all the associated fields (ie 'user_id' in the 'actions' table won't be updated..etc etc).

If so, here's how:

So - create a duplicate of your database (or tables) as back-up. You'll then probably want to rename the 'id' field to 'autoid', create another id field CHAR(36), run a script to populate all the UUIDs, then another script that populates the associated ids (ie 'user_id' in the 'actions' table) with the corresponding UUID.

CakePHP code that generates UUIDs:

Here's the link to creating a UUID in CakePHP 1.2: http://book.cakephp.org/1.2/en/view/826/uuid