Set<Object> getPartitions(List<Document> documents) {
final HashSet<Object> partitions = Sets.newHashSet();
for (Document document : documents) {
final Collection<Object> documentPartitions =
document.<Collection<Object>>getField(partitionIdFieldName);
if (documentPartitions != null) {
partitions.addAll(documentPartitions);
}
}
return partitions;
}
