presto-main/src/main/java/io/prestosql/operator/aggregation/ApproximateCountDistinctAggregation.java/ApproximateCountDistinctAggregation/getOrCreateHyperLogLog
class ApproximateCountDistinctAggregation:    private static HyperLogLog getOrCreateHyperLogLog(HyperLogLogState state, double maxStandardError)
    {
        HyperLogLog hll = state.getHyperLogLog();
        if (hll == null) {
            hll = HyperLogLog.newInstance(standardErrorToBuckets(maxStandardError));
            state.setHyperLogLog(hll);
            state.addMemoryUsage(hll.estimatedInMemorySize());
        }
        return hll;
    }