[Monetdb-developers] MonetDB XQuery Module Crash

Stefan Manegold Stefan.Manegold at cwi.nl
Sun Jul 9 16:24:15 CEST 2006


Hi Michael,

thank you very much for being interested in and using MonetDB/XQuery,
as well as for reporting your problem!

Apparently, the mailinglist information on the FAQ page of the
MonetDB/XQUery web site is indeed a bit misleading.
There are actually no specific MonetDB/*XQuery* mailing lists,
but "only" general mailing lists for MonetDB that are supposed 
to be used for all communication about/around MonetDB and all
of it's companions and front-ends, o.a., MonetDB/SQL & MonetDB/XQuery;
see http://monetdb.cwi.nl/News/MailChannels/ for details.

Sorry for the inconvenience!
We'll update the info on the web site.
And I feel free to propagate this discussion to the Monetdb-users list.

Wrt. your actual problem, I have a couple of questions, maily requesting
more information to analyse the problem:

What kind of system are you running MonetDB/XQuery on?
	CPU (type, 32- or 64-bit)?
	amount of memory?
	free disk space?
	operating system (type, 32- or 64-bit)?

How did you install MonetDB/XQuery? Using binary (.rpm or .msi) packages or
compiling from source (tarball or from CVS)?

Which queries are you running? Which of them are working with up to 50MB but
fail with 100MB or more?

Did you load/shred your document explicitely via the "shred_doc" MIL command
on the Mserver console, or did you have them loaded/shreded implicitely on
the fly via the fn:doc() XQuery function?

In the latter case, you could try whether the failing queries do work in
larger documents once you increase the XML document cache limit by staring
Mserver with "--set xquery_cacheMB=<size>" where size is large than the
default 100, e.g., just larger than your largest document.
(Admittedly, there is only very little "well hidden" documentation about the
 "--set" option(s) of Mserver; we're working on that...)

If this helps, then there might be a bug somewhere in our document caching
code...

Kind regards,

Stefan

On Sun, Jul 09, 2006 at 03:54:30PM +0200, Michael Schmidt wrote:
> Hi all,
> 
> I'm confused as I expected a MonetDB XQuery users mailing list instead of
> a developer list. However, this list was linked in the MonetDB/XQuery FAQ
> section so I thought it would be worth trying...
> 
> Here is my problem: I'm just running some XQuery benchmarks using MonetDB
> together with the XQuery module. Installation was ok and I have chosen a
> set of queries to be evaluated against data generated with the xmlgen
> tool. Query processing works fine for 10MB and 50MB documents, but when
> processing large documents (100MB and 200MB) the client reports an error
> message. I even tried to figure out the source of the problem using trace
> option -t but do not understand the listed error messages. Here is the
> final error message reported by the client:
> 
> ERROR: [rename]: 29 times inserted nil due to errors at tuples "pre_size", "pre_level", "pre_prop", "pre_kind", "qn_uri", "qn_prefix".
> ERROR: [rename]: first error was:
> ERROR: rename(<tmp_351>,pre_size2): operation failed
> ERROR: interpret_unpin: [rename] bat=171,stamp=-1285 OVERWRITTEN
> ERROR: BBPdecref: tmp_253 does not have pointer fixes.
> ERROR: interpret_params: +(param 2): evaluation error.
> 
> Once again: evaluation of the same queries works fine on small streams but
> fails on large streams. By the way, I've installed the latest offcial
> release of both the server and the XQuery module.
> 
> Is this a bug or are there any default memory limits causing the crash? I
> tried to figure out what the --set option is good for but was not able to
> detect any documentation on supported options.
> 
> Kind regards
> Michael
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-- 
| Dr. Stefan Manegold | mailto:Stefan.Manegold at cwi.nl |
| CWI,  P.O.Box 94079 | http://www.cwi.nl/~manegold/  |
| 1090 GB Amsterdam   | Tel.: +31 (20) 592-4212       |
| The Netherlands     | Fax : +31 (20) 592-4312       |




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