[horde] Database cleanup horde_histories

[Jens Wahnes]

Michael J Rubinsky wrote:
> The history data doesn't really have anything to do with the *display* 
> of entries. If the entry in question still exists in the application's 
> backend storage, the entry will display fine. In general, the history 
> data is used for synchronization of things like ActiveSync clients on a 
> mobile device, or *DAV clients. If you don't care about synchronization 
> it is generally safe to delete this information. Even if you do care 
> about synchronization, it would generally be safe to delete REALLY old 
> entries - basically as long as any clients you care about have 
> synchronized since the history event date, you should be fine.

Thank you for explaining.

I think the trouble really comes in when there are in fact entries of 
the kind I mentioned previously (e.g. monthly meeting entered into a 
group calendar by someone who has long left the workgroup). When the 
history records are incomplete, and there are members joining and 
leaving the workgroup all the time, there will be issues with syncing 
these recurring events (e.g. to mobile devices with reminders supposed 
to be popping up there).

> Note that history data might have auditing value in your organization, 
> so that is also something to keep in mind as well.

We're pretty much in the opposite situation. We must not keep records of 
personal data according to GDPR statutes, at least when these 
individuals are no longer affiliated with our organization. It's hard to 
meet these different goals at the same time, but still we strive to do 
our best -- any help how to improve this appreciated.


Jens