presto-hive/src/main/java/io/prestosql/plugin/hive/HiveWriter.java/HiveWriter/append
class HiveWriter:    public void append(Page dataPage)
    {
        // getRegionSizeInBytes for each row can be expensive; use getRetainedSizeInBytes for estimation
        hiveWriterStats.addInputPageSizesInBytes(dataPage.getRetainedSizeInBytes());
        fileWriter.appendRows(dataPage);
        rowCount += dataPage.getPositionCount();
        inputSizeInBytes += dataPage.getSizeInBytes();
    }