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Comment by merb | Hacker News Reader

well I'm pretty sure all these ways to delete your facebook stuff will only soft delete it. I mean it's way more sane to do:

    UPDATE picture SET date_deleted = now() WHERE picture_id = ?

instead of actually deleting it, because so you can recreate something if people deleted their stuff by accident. Means facebook probably still has your data.

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Yep, this is how pretty much every large data warehouse works as well. It's very useful to be able to say "What was the state of everything at time X", even if it's been deleted you want to be able to see the state at certain times.

I also imagine with all the data that FB has, they probably have a legal obligation to keep data as it can be useful in solving crimes or gathering evidence. In fact their TOS explicitly states that they will preserve data: "We may access, preserve and share your information in response to a legal request"

i think that's only after they received a request.

That soft delete is the next evolution you learn after learning not to issue SQL DELETE instead. But after that it would be more like event sourcing where an event to delete was issued. And then some sort of snapshot creator would translate that to it's current dataset/view as not being in the data.

The event source can always be replayed to see the data at any point in time, including recreating stuff.

Do we know if Facebook stores the revision history of a given status or comment? Would it be possible to programmatically overwrite every status and comment?

> Do we know if Facebook stores the revision history of a given status or comment? Would it be possible to programmatically overwrite every status and comment?

Yes. Facebook does. There's a quora question that asks "Why does Facebook provide an edit/revision history for edits made to comments?" https://i.imgur.com/GW0x500.png https://archive.fo/EKzQx

One answer says:

> I think its simply so you can see what was their originally. People are allowed to edit their comments now and they could write something one minute, get alot of likes and totally switch it to something else. If the comment starts off with something nice like "Have a nice day" and people like it and afterwards the person who wrote the comment comes back and changes it to something negative, then that would make you look bad. So it is there to make sure everyone can see what was originally there.

Another answer says

> Yes. It allows the audience to keep the content editor accountable for their actions. The transparency in information sets clear expectations for both the content producer and consumer.

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