code: private void runWithCardinalityUnknown(
        Parameters params,
        TopNResultBuilder resultBuilder,
        @Nullable TopNQueryMetrics queryMetrics
    )
    {
      DimValAggregateStore aggregatesStore = makeDimValAggregateStore(params);
      if (queryMetrics != null) {
        queryMetrics.startRecordingScanTime();
      }
      long processedRows = scanAndAggregate(params, null, aggregatesStore);
      updateResults(params, null, aggregatesStore, resultBuilder);
      closeAggregators(aggregatesStore);
      params.getCursor().reset();
      if (queryMetrics != null) {
        queryMetrics.addProcessedRows(processedRows);
        queryMetrics.stopRecordingScanTime();
      }
    }
docs: This function currently handles TopNs on long and float columns, which do not provide cardinality or an ID lookup.
  When cardinality is unknown, process everything in one pass.
  Existing implementations of makeDimValSelector() require cardinality as well, so the DimValSelector is not used.
  
  @param params        TopN parameters from run()
  @param resultBuilder Result builder from run()