[xquery-talk] Re: The State of Native XML databases

[Michael Rys]

Ron: one way to deal with that is to use intentional locks... look in Gray/Reuter under tree locking algorithms.

Ilya: I don't see what the problem with ordering is. Of course it needs to be preserved and there are implementation strategies to do that without impacting the otherwise unaffected neighbors...

Best regards
Michael

-----Original Message-----
From: talk-bounces at x-query.com [mailto:talk-bounces at x-query.com] On Behalf Of Ilya Sterin
Sent: Tuesday, August 21, 2007 12:48 PM
To: Ronald Bourret
Cc: talk at xquery.com
Subject: Re: [xquery-talk] Re: The State of Native XML databases

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 <rpbourret at rpbourret.com> 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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