Re: [db-wg] Clean up of unreferenced person/role objects

[Shane Kerr <]

All,

On Wed, Apr 18, 2007 at 01:34:54PM +0200, Denis Walker wrote:
> 
> One time bulk cleanup procedure
> -------------------------------
> 
> Month 1
> 
>     * Select 80,000 unreferenced person/role objects.
> 
> Month 2
> 
>     * Check selected person/role objects.
>     * Those still unreferenced:
>           o Delete using normal update process.
>           o 2000 objects per update message.
>           o Run updates overnight (Saturday/Sunday).
>           o One update every 15 minutes.
>           o This should avoid any unnecessary load on the servers.
>     * Select next 80,000 unreferenced person/role objects.
> 
> Month 3
> 
>     * Repeat process until complete.

This makes sense to me, for a one-time cleanup.

> The worst problem that can occur is that someone will enter a
> reference to their person/role object just as we delete it. However,
> as we are only deleting unreferenced person/role objects, the time
> needed to re-create them is minimal. We suspect that a very large
> proportion of the unreferenced person/role objects that we will be
> deleting are abandoned objects that are no longer used.

A bit of thinking can come up with some scenerios that might be
worse(*).

I definitely think any minor problems are more than outweighed by the
removal of unused personal data! 

--
Shane

(*) For example, a worse problem would be referencing the wrong
person/role object. This can happen like so:

- Person object X created
- Months pass...
- Person object X deleted by this process
- Person object Y created with same "nic-hdl:" as object X
- User who created person object X decides to use it, but actually
  refers to object Y (since it has the same "nic-hdl:")

The user who created person object X assumes it is still fine, because
the usual notification was not received, and in any case it was
probably protected by "mnt-by:".

Of course, this is an unlikely corner case. :)