// Read the new part of the parents array from the positions:
TermPositions positions = indexReader.termPositions(
new Term(Consts.FIELD_PAYLOADS, Consts.PAYLOAD_PARENT));
try {
if (!positions.skipTo(first) && first < num) {
throw new CorruptIndexException("Missing parent data for category " + first);
}
for (int i=first; i<num; i++) {
// Note that we know positions.doc() >= i (this is an
// invariant kept throughout this loop)