presto-main/src/main/java/io/prestosql/operator/PartitionedOutputOperator.java/PagePartitioner/appendRow
class PagePartitioner:        private void appendRow(PageBuilder pageBuilder, Page page, int position)
        {
            pageBuilder.declarePosition();

            for (int channel = 0; channel < sourceTypes.size(); channel++) {
                Type type = sourceTypes.get(channel);
                type.appendTo(page.getBlock(channel), position, pageBuilder.getBlockBuilder(channel));
            }
        }