presto-orc/src/main/java/io/prestosql/orc/writer/StructColumnWriter.java/StructColumnWriter/writeBlock
class StructColumnWriter:    @Override
    public void writeBlock(Block block)
    {
        checkState(!closed);
        checkArgument(block.getPositionCount() > 0, "Block is empty");

        ColumnarRow columnarRow = toColumnarRow(block);
        writeColumnarRow(columnarRow);
    }