presto-main/src/main/java/io/prestosql/operator/aggregation/RealCovarianceAggregation.java/RealCovarianceAggregation/covarPop
class RealCovarianceAggregation:    @AggregationFunction("covar_pop")
    @OutputFunction(StandardTypes.REAL)
    public static void covarPop(@AggregationState CovarianceState state, BlockBuilder out)
    {
        if (state.getCount() == 0) {
            out.appendNull();
        }
        else {
            double result = getCovariancePopulation(state);
            REAL.writeLong(out, Float.floatToRawIntBits((float) result));
        }
    }