Re: Move using initial state

On 06.09.2013 17:50, Philip Martin wrote:
> Philip Martin <philip.martin_at_wandisco.com> writes:
>
>> What about alter_dir? I think the rule is that alter_dir on a directory
>> should occur before add or delete affects the children of the directory.
>> There is also a rule:
>>
>> * - The ancestor of an added, copied-here, moved-here, or
>> * modified node may not be deleted. The ancestor may not be moved
>> * (instead: perform the move, *then* the edits).
> I've been thinking about alter_dir and I see no reason, in the update
> editor at least, for a rule that requires alter_dir before adding or
> removing children. The Ev2 "once" rule is designed to ensure that Ev2
> actions can be applied to the nodes in the working copy as the actions
> are received and that the working copy nodes will always reflect
> repository nodes. This doesn't require alter_dir on the parent before
> add/delete of children.

Actually, the Once Rule is way more important for server implementations
than client implementations. It effectively defines when the server can
commit changes to a node and assume no further changes will happen
later. That's quite a nice property to have when you're designing
caching strategies; especially if writes are orders of magnitude more
expensive than reads, which is the norm for distributed databases -- and
even for plain vanilla filesystems.

-- Brane

-- 
Branko Čibej | Director of Subversion
WANdisco // Non-Stop Data
e. brane_at_wandisco.com