Allow users to remove their account

I am developing a gallery which allows users to post photos, comments, vote and do many other tasks.

Now I think that it is correct to allow users to unsubscribe and remove all their data if they want to. However it is difficult to allow such a thing because you run the risk to break your application (e.g. what should I do when a comment has many replies? what should I do with pages that have many revisions by different users?).

Photos can be easily removed, but for other data (i.e. comments, revisions...) I thought that there are three possibilities:

assign it to the admin
assign it to a user called "removed-user"
mantain the current associations (i.e. the user ID) and only rename user's data (e.g. assign a new username such as "removed-user-24" and a non-existent e-mail such as "noreply-removed-user-24@mysite.com"

What are the best practices to follow when we allow users to remove their accounts? How do you implement them (particularly in Rails)?

Solution

Ideally in a system you would not want to "hard delete" data. The best way I know of and that we have implemented in past is "soft delete". Maintain a status column in all your data tables which ideally refers to the fact whether the row is active or not. Any row when created is "Active" by default; however as entries are deleted; they are made inactive.

All select queries which display data on screen filter results for only "active records". This way you get following advantages: 1. Data Recovery is possible. 2. You can have a scheduled task on database level, which can take care of hard deletes of once in a way; if really needed. (Like a SQL procedure or something) 3. You can have an admin screen to be able to decide which accounts, entries etc you'd really want to mark for deletion 4. A temperory disabling of account can also be implemented with same solution.

In prod environments where I have worked on, a hard delete is a strict No-No. Infact audits are maintained for deletes also. But if application is really small; it'd be upto user.

I would still suggest a "virtual delete" or a "soft delete" with periodic cleanup on db level; which will be faster efficient and optimized way of cleaning up.