Hi Huib, to reproduce and investigate your problems, it would be very helpful for us if you could provide us with (access to) (scaled-down versions of) your documents (how big are they originally?) on which the problems (still) occur for you. Stefan On Tue, Nov 27, 2007 at 10:53:43AM +0100, Huib Verweij wrote:

Hi everyone,

I'm new to MonetDB XQuery and have written a crude Cocoon generator for MonetDB using the example code for the JDBC client from the website.

I am using the latest Bug Fix Release of MonetDB as announced by Sjoerd Mullender on 24-10-2007. When I execute the following query I get an error:

--------------------------------------------------------- let $zz := doc('vogels.xml')//Vogels[data(Dwaalgast) = 'zeer zeldzaam']

return <vogeltjes>{$zz}</vogeltjes> ---------------------------------------------------------

throws:

java.sql.SQLException: ERROR: ERROR: XML Generation: NULL BAT has a 4415 head, but tail is NULL. ERROR: ERROR: xquery_print_result_loop: operation failed.

However, when I change the XQuery to:

--------------------------------------------------------- let $zz := doc('vogels.xml')//Vogels[data(Dwaalgast) = 'zeer zeldzaam']

return <vogeltjes>{$zz}azaz</vogeltjes> ---------------------------------------------------------

everything's OK and I get the proper result. (The previous release threw the same error btw.)

Also, when I join the results from the above query with another table to resolve some codes to code-descriptions, the query takes from 8.5 up to 11 seconds to execute, vs. <1 second for a query without the join. The result is a little over 1Mb in size. The query I use is this:

--------------------------------------------------------- let $zz := doc('vogels.xml')//Vogels[Ecotoop_x0020_nest]

return <vogeltjes> {for $vogel in doc('vogels.xml')//Vogels[Ecotoop_x0020_nest], $vc in doc('vogels-code.xml')//Vogels-code[data(Kolomnaam) = 'Ecotoop nest'][data(Code) = $vogel/Ecotoop_x0020_nest]/Codebeschrijving return <vogel> {$vogel/*} {$vc} </vogel> } </vogeltjes> ---------------------------------------------------------

The latest preview release of eXist handles the join in 3.1 seconds, any ideas on why this join takes almost three times as long?

I have a final question: how do I specify external variables using the JDBC client?

Regards,

Huib Verweij.

-- | Dr. Stefan Manegold | mailto:Stefan.Manegold@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 |