Hi there,
I'm evaluating Sedna and have troubles executing some queries. To be
more precisely, I'm using Sedna 3.1.126, Sedna XML:DB API 1.2 RC3, Sun
JDK 1.6.0_11 on Windows XP Professional x86. The problem mainly occurrs
on larger collections (more than 300,000 xml files) and for more complex
XQueries.
The error message I get looks like:
Client did not understand instruction 1196639556, body length = 0.
Exception in thread "main" java.lang.NullPointerException
at net.cfoster.sedna.xmldb.n.a(Unknown Source)
at net.cfoster.sedna.xmldb.i.hasMoreResources(Unknown Source)
at net.cfoster.sedna.xmldb.x.hasMoreResources(Unknown Source)
[...]
Client did not understand instruction 1196639556, body length = 1312890957.
Exception in thread "Thread-0" java.lang.NullPointerException
at net.cfoster.sedna.xmldb.n.a(Unknown Source)
at net.cfoster.sedna.xmldb.y.e(Unknown Source)
at net.cfoster.sedna.xmldb.t.a(Unknown Source)
at net.cfoster.sedna.xmldb.j.run(Unknown Source)
at java.lang.Thread.run(Thread.java:619)
One XQuery which does not work as expected (it works fine for smaller
collections!) is:
let $role := "customer"
let $type := "invoice"
for $yearAndMonth in fn:distinct-values(index-scan("index_0", $type,
"EQ")[...@date][fn:matches(@sum,
"^[0-9]+(\.[0-9]+)?$")]/fn:substring(@date, 1, 7))
let $headers := (
for $header in index-scan("index_1", $role,
"EQ")[names/name/text()][references/referen...@type =
$type][fn:matches(@date, fn:concat("^",
$yearAndMonth))][fn:matches(@sum, "^[0-9]+(\.[0-9]+)?$")]]
order by $header/references/referen...@type = $type][fn:matches(@date,
fn:concat("^", $yearAndMonth))][fn:matches(@sum,
"^[0-9]+(\.[0-9]+)?$")]/xs:double(@sum) descending
return
$header
)
let $topHeader := fn:subsequence($headers, 1, 1)
let $date := fn:string($topHeader/references/referen...@type =
$type][fn:matches(@date, fn:concat("^",
$yearAndMonth))][fn:matches(@sum, "^[0-9]+(\.[0-9]+)?$")]/@date)
let $name := $topHeader/names/na...@role = $role]/text()
let $sum := $topHeader/references/referen...@type =
$type][fn:matches(@date, fn:concat("^",
$yearAndMonth))][fn:matches(@sum, "^[0-9]+(\.[0-9]+)?$")]/xs:double(@sum)
order by $yearAndMonth ascending
return
<resultSet><date>{ $date }</date><name>{ $name }</name><sum>{
fn:round-half-to-even($sum, 2) }</sum></resultSet>
Both indizes I use in this query are created with:
create index "index_0"
on fn:collection("test")/header/references/reference
by @type
as xs:string
create index "index_1"
on fn:collection("test")/header
by names/name/@role
as xs:string
The important lines of the Java code to execute XQueries are:
public class Sedna {
private Collection collection;
public void connect() {
Database database = (Database)
Class.forName("net.cfoster.sedna.DatabaseImpl").newInstance();
DatabaseManager.registerDatabase(database);
collection =
DatabaseManager.getCollection("xmldb:sedna://localhost:5050/test/test",
"SYSTEM", "MANAGER");
}
public void execute(String xQuery) {
XQueryService xQueryService = (XQueryService)
collection.getService("XQueryService", "1.0");
ResourceSet resourceSet = xQueryService.query(xQuery);
ResourceIterator resourceIterator = resourceSet.getIterator();
StringBuffer stringBuffer = new StringBuffer();
while (resourceIterator.hasMoreResources() == true) {
Resource resource = resourceIterator.nextResource();
stringBuffer.append(resource.getContent().toString());
stringBuffer.append('\n');
}
return stringBuffer.toString();
}
public void disconnect() {
collection.close();
}
}
Does anybody know what I could try to avoid this error? Is there
something I've missed or a workaround for this problem? How can I tune
Sedna and/or my XQuery to improve performance?
Thanks a lot!
Andreas Meinl
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