presto-main/src/main/java/io/prestosql/operator/aggregation/state/DigestAndPercentileStateFactory.java/GroupedDigestAndPercentileState/ensureCapacity
class GroupedDigestAndPercentileState:        @Override
        public void ensureCapacity(long size)
        {
            digests.ensureCapacity(size);
            percentiles.ensureCapacity(size);
        }