presto-main/src/main/java/io/prestosql/operator/aggregation/ApproximateLongPercentileArrayAggregations.java/ApproximateLongPercentileArrayAggregations/initializeDigest
class ApproximateLongPercentileArrayAggregations:    private static void initializeDigest(@AggregationState DigestAndPercentileArrayState state)
    {
        QuantileDigest digest = state.getDigest();
        if (digest == null) {
            digest = new QuantileDigest(0.01);
            state.setDigest(digest);
            state.addMemoryUsage(digest.estimatedInMemorySizeInBytes());
        }
    }