XdmNode doc = vsource.read();
if (doc == null || vsource.moreDocuments()) {
throw XProcException.dynamicError(3);
}
matcher = new ProcessMatch(runtime, this);
// FIXME: Only do this if we really need to!
sequenceLength = matcher.count(doc, match, false);
runtime.getXProcData().setIterationSize(sequenceLength);