@Override
public Value value(final QueryContext qc) throws QueryException {
final FItem getKey = checkArity(exprs[1], 1, qc);
final long k = Math.min(toLong(exprs[2], qc), Integer.MAX_VALUE);
if (k < 1) return Empty.SEQ;
final Iter iter = exprs[0].iter(qc);
final MinHeap<Item, Item> heap =
new MinHeap<>(
new Comparator<Item>() {
@Override
public int compare(final Item it1, final Item it2) {
try {
return OpV.LT.eval(it1, it2, sc.collation, sc, info) ? -1 : 1;
} catch (final QueryException qe) {
throw new QueryRTException(qe);
}
}
});
try {
for (Item it; (it = iter.next()) != null; ) {
heap.insert(checkNoEmpty(getKey.invokeItem(qc, info, it)), it);
if (heap.size() > k) heap.removeMin();
}
} catch (final QueryRTException ex) {
throw ex.getCause();
}
final ValueBuilder vb = new ValueBuilder();
while (!heap.isEmpty()) vb.addFront(heap.removeMin());
return vb.value();
}
@Override
public Value value(final QueryContext qc) throws QueryException {
final FItem f = checkArity(exprs[1], 1, qc);
final Iter iter = exprs[0].iter(qc);
Item it = iter.next();
if (it == null) return Empty.SEQ;
final Value v1 = f.invokeValue(qc, info, it);
it = iter.next();
if (it == null) return v1;
final ValueBuilder vb = new ValueBuilder().add(v1);
do {
vb.add(f.invokeValue(qc, info, it));
} while ((it = iter.next()) != null);
return vb.value();
}