presto-main/src/main/java/io/prestosql/sql/planner/plan/StatisticAggregationsDescriptor.java/StatisticAggregationsDescriptor/serialize
class StatisticAggregationsDescriptor:        @VisibleForTesting
        static String serialize(ColumnStatisticMetadata value)
        {
            return value.getStatisticType().name() + ":" + value.getColumnName();
        }