presto-hive/src/main/java/io/prestosql/plugin/hive/util/Statistics.java/Statistics/createColumnToComputedStatisticsMap
class Statistics:    private static Map<String, Map<ColumnStatisticType, Block>> createColumnToComputedStatisticsMap(Map<ColumnStatisticMetadata, Block> computedStatistics)
    {
        Map<String, Map<ColumnStatisticType, Block>> result = new HashMap<>();
        computedStatistics.forEach((metadata, block) -> {
            Map<ColumnStatisticType, Block> columnStatistics = result.computeIfAbsent(metadata.getColumnName(), key -> new HashMap<>());
            columnStatistics.put(metadata.getStatisticType(), block);
        });
        return result.entrySet()
                .stream()
                .collect(toImmutableMap(Entry::getKey, entry -> ImmutableMap.copyOf(entry.getValue())));
    }