presto-orc/src/main/java/io/prestosql/orc/OrcWriteValidation.java/OrcWriteValidation/addRowGroupStatistics
class OrcWriteValidation:        public void addRowGroupStatistics(Map<OrcColumnId, ColumnStatistics> columnStatistics)
        {
            RowGroupStatistics rowGroupStatistics = new RowGroupStatistics(validationMode, columnStatistics);
            currentRowGroupStatistics.add(rowGroupStatistics);

            retainedSize += RowGroupStatistics.INSTANCE_SIZE;
            if (validationMode != HASHED) {
                for (ColumnStatistics statistics : rowGroupStatistics.getColumnStatistics().values()) {
                    retainedSize += Integer.BYTES + statistics.getRetainedSizeInBytes();
                }
            }
        }