presto-main/src/main/java/io/prestosql/operator/aggregation/RealHistogramAggregation.java/RealHistogramAggregation/output
class RealHistogramAggregation:    @OutputFunction("map(real,real)")
    public static void output(@AggregationState DoubleHistogramAggregation.State state, BlockBuilder out)
    {
        if (state.get() == null) {
            out.appendNull();
        }
        else {
            Map<Double, Double> value = state.get().getBuckets();
            BlockBuilder entryBuilder = out.beginBlockEntry();
            for (Map.Entry<Double, Double> entry : value.entrySet()) {
                REAL.writeLong(entryBuilder, floatToRawIntBits(entry.getKey().floatValue()));
                REAL.writeLong(entryBuilder, floatToRawIntBits(entry.getValue().floatValue()));
            }
            out.closeEntry();
        }
    }