Maybe a bit late for this time, but might help next time: history of moved files is still in CVS at their original location, see cvs -d<user>@monetdb.cvs.sourceforge.net:/cvsroot/monetdb rlog -N clients/src/java/src/nl/cwi/monetdb/jdbc/MonetConnection.java Stefan On Wed, Feb 20, 2008 at 07:50:26PM +0000, Fabian wrote:

Update of /cvsroot/monetdb/java/src/nl/cwi/monetdb/jdbc In directory sc8-pr-cvs16.sourceforge.net:/tmp/cvs-serv12362/src/nl/cwi/monetdb/jdbc

Modified Files: MonetConnection.java Log Message: Fix for bug #1886326: MonetDB JDBC driver exception for XQuery with no results

2 and a half hour later ... Due to missing history (cvs moves) and missing documentation (on my end) it took quite some while to figure out what was the "correct" way to solve this bug. In the end it al boiled down on the limitation of the XQuery backend to only support full-results-at-once, which means the resource allocation of JDBC needs to allocate the entire result at once. If the result is 0 rows big, however, then things went wrong when calculating the current cache block. Anyway, for the future we now know why we did this cache block calulation thing like this again...

Index: MonetConnection.java =================================================================== RCS file: /cvsroot/monetdb/java/src/nl/cwi/monetdb/jdbc/MonetConnection.java,v retrieving revision 1.2 retrieving revision 1.3 diff -u -d -r1.2 -r1.3 --- MonetConnection.java 11 Jan 2008 10:36:16 -0000 1.2 +++ MonetConnection.java 20 Feb 2008 19:50:24 -0000 1.3 @@ -1164,7 +1164,17 @@ isSet = new boolean[7]; this.parent = parent; if (parent.cachesize == 0) { - cacheSize = lang == LANG_SQL ? MonetConnection.DEF_FETCHSIZE : tuplecount; + /* Below we have to calculate how many "chunks" we need + * to allocate to store the entire result. However, if + * the user didn't set a cache size, as in this case, we + * need to stick to our defaults. So far, so good. Now + * the problem with XQuery is, that it doesn't support + * any block fetching, so we need to always fetch + * everything at once. For that reason, the cache size + * is here set to the tuplecount, such that we do a full + * fetch at once. To avoid a division by zero lateron, + * we make sure the cache size is not 0 */ + cacheSize = lang == LANG_SQL ? MonetConnection.DEF_FETCHSIZE : (tuplecount + 1); cacheSizeSetExplicitly = false; } else { cacheSize = parent.cachesize;

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