Re: The State of Native XML databases

[Ilya Sterin]

Ron, not sure what you mean.  If you're updating a node, how would a
parent's child count effect it's update?  These updates should be
performed in a committed isolation level with non-repeatable reads.
Now, one issue is to ensure the consistency of node ordering, which of
course in the relational world is non-existent since a relation is
just an unordered set of tuples.  I'm wondering how ordering is
preserved.



On 8/21/07, Ronald Bourret <http://x-query.com/mailman/listinfo/talk> wrote:
> There's an additional problem here.
>
> If you're updating a particular node, you probably want to lock the
> ancestors of the node as well, so that nobody can delete them, as this
> would conflict with your update in a rather major way. Taken to an
> extreme, this effectively locks the entire document.
>
> I'd be curious to know how node-locking (or page-locking) databases
> handle this problem. Perhaps there are "no-delete" locks placed on the
> ancestors?
>
> -- Ron
>
> Jeff Dexter wrote:
> > On a side note, while node level locks may be the most granular, some update
> > operations may require locking multiple nodes. For instance, if you replace
> > an element that has attributes and children, a lock of the element may imply
> > a lock of its attributes and descendants as well.
>
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