Lukas: Thanks for the feedback. This is pretty nasty though as it makes bulk updates pretty much unpractical in a multi-user environment. My current query was something like: delete node /codeBook/dataDscr/var/catstat which basically deletes all the catstat element in teh database at once Would this be one transaction or many transactions? for $var in /codeBook/dataDscr/var delete node $var/catstat It may stilll push my CPU to 100% though. Would there be a way to set a priority for queries? For example, I may want my regular search/retrieval queries to run at higher priority than the above update so users still get served in a reasonable amount of time? best *P On 11/4/11 7:25 AM, Lukas Kircher wrote:

Hi Pascal,

this behavior is part of the BaseX transaction management. As XQuery Update allows to alter multiple databases within the same query/transaction, updating statements are executed in isolation - which means no other transactions are allowed during evaluation of an updating transaction.

You can find more about this here [1]. But, depending on your use case, there might be a workaround (i.e. performing updates on a copy, etc...).

Cheers, Lukas

[1] http://docs.basex.org/wiki/Transaction_Management

On Fri, Nov 4, 2011 at 3:39 AM, Pascal Heus <pascal.heus@gmail.com <mailto:pascal.heus@gmail.com>> wrote:

All: I'm running an long "xquery delete node" on one of my database and this pretty much seem to make my server unavailable for other operations. I expect this query to run for a few hours (affecting a few million nodes, database is around 800Mb). I'm running this on a Amazon EC2 small instance (1 CPU, 1.7Gb RAM) and the CPU has been stuck at 100%. If I attempt to query any database on the server (not only the one being updated), I basically don't get anything back. So do heavy xquery update requests basically lock down the server? Anyone else having similar experience? Feedback/suggestions? best *P _______________________________________________ BaseX-Talk mailing list BaseX-Talk@mailman.uni-konstanz.de <mailto:BaseX-Talk@mailman.uni-konstanz.de> https://mailman.uni-konstanz.de/mailman/listinfo/basex-talk

Hi Pascal, I can give you some promising prospects: yesterday, we did some brainstorming how to best extend the BaseX architecture to concurrent readers and writers (possibly by switching to MVCC), and concurrent write operations on multiple datbases. Work is in progress, but I'm positive that we'll soon be able to offer a solution that gives you (and everyone) more freedom for many updating use cases. In the short run, one feasible approach is to perform updates in one BaseX and database instance, and then replace the obsolete database instance with the updated one. We'll keep you updated, Christian ___________________________ On Fri, Nov 4, 2011 at 3:16 PM, Pascal Heus <pascal.heus@gmail.com> wrote:

Lukas: Thanks for the feedback. This is pretty nasty though as it makes bulk updates pretty much unpractical in a multi-user environment.

My current query was something like: delete node /codeBook/dataDscr/var/catstat which basically deletes all the catstat element in teh database at once

Would this be one transaction or many transactions? for $var in /codeBook/dataDscr/var delete node $var/catstat

It may stilll push my CPU to 100% though. Would there be a way to set a priority for queries? For example, I may want my regular search/retrieval queries to run at higher priority than the above update so users still get served in a reasonable amount of time?

best *P