presto-orc/src/main/java/io/prestosql/orc/writer/BooleanColumnWriter.java/BooleanColumnWriter/finishRowGroup
class BooleanColumnWriter:    @Override
    public Map<OrcColumnId, ColumnStatistics> finishRowGroup()
    {
        checkState(!closed);
        ColumnStatistics statistics = statisticsBuilder.buildColumnStatistics();
        rowGroupColumnStatistics.add(statistics);
        statisticsBuilder = new BooleanStatisticsBuilder();
        return ImmutableMap.of(columnId, statistics);
    }