if (outputNodes.size() > 0) {
TimeSequence timestamp = null;
for (int iNode = 0; iNode < outputNodes.size(); iNode++) {
DatabaseElementNode node = outputNodes.get(iNode);
if (timestamp != null) {
timestamp = timestamp.union(node.getTimestamp());
} else {
timestamp = node.getTimestamp();
}
}
DatabaseGroupNode result = new ResultGroupNode(_resultSchema, timestamp);