rocksdb::Status Hash::RangeByLex()

in src/types/redis_hash.cc [298:353]
53 lines of code
28 McCabe index (conditional complexity)

rocksdb::Status Hash::RangeByLex(engine::Context &ctx, const Slice &user_key, const RangeLexSpec &spec,
                                 std::vector<FieldValue> *field_values) {
  field_values->clear();
  if (spec.count == 0) {
    return rocksdb::Status::OK();
  }
  std::string ns_key = AppendNamespacePrefix(user_key);
  HashMetadata metadata(false);
  rocksdb::Status s = GetMetadata(ctx, ns_key, &metadata);
  if (!s.ok()) return s.IsNotFound() ? rocksdb::Status::OK() : s;

  std::string start_member = spec.reversed ? spec.max : spec.min;
  std::string start_key = InternalKey(ns_key, start_member, metadata.version, storage_->IsSlotIdEncoded()).Encode();
  std::string prefix_key = InternalKey(ns_key, "", metadata.version, storage_->IsSlotIdEncoded()).Encode();
  std::string next_version_prefix_key =
      InternalKey(ns_key, "", metadata.version + 1, storage_->IsSlotIdEncoded()).Encode();
  rocksdb::ReadOptions read_options = ctx.DefaultScanOptions();
  rocksdb::Slice upper_bound(next_version_prefix_key);
  read_options.iterate_upper_bound = &upper_bound;
  rocksdb::Slice lower_bound(prefix_key);
  read_options.iterate_lower_bound = &lower_bound;

  auto iter = util::UniqueIterator(ctx, read_options);
  if (!spec.reversed) {
    iter->Seek(start_key);
  } else {
    if (spec.max_infinite) {
      iter->SeekToLast();
    } else {
      iter->SeekForPrev(start_key);
    }
  }
  int64_t pos = 0;
  for (; iter->Valid() && iter->key().starts_with(prefix_key); (!spec.reversed ? iter->Next() : iter->Prev())) {
    InternalKey ikey(iter->key(), storage_->IsSlotIdEncoded());
    if (spec.reversed) {
      if (ikey.GetSubKey().ToString() < spec.min || (spec.minex && ikey.GetSubKey().ToString() == spec.min)) {
        break;
      }
      if ((spec.maxex && ikey.GetSubKey().ToString() == spec.max) ||
          (!spec.max_infinite && ikey.GetSubKey().ToString() > spec.max)) {
        continue;
      }
    } else {
      if (spec.minex && ikey.GetSubKey().ToString() == spec.min) continue;  // the min member was exclusive
      if ((spec.maxex && ikey.GetSubKey().ToString() == spec.max) ||
          (!spec.max_infinite && ikey.GetSubKey().ToString() > spec.max))
        break;
    }
    if (spec.offset >= 0 && pos++ < spec.offset) continue;

    field_values->emplace_back(ikey.GetSubKey().ToString(), iter->value().ToString());
    if (spec.count > 0 && field_values->size() >= static_cast<unsigned>(spec.count)) break;
  }
  return rocksdb::Status::OK();
}