presto-spi/src/main/java/io/prestosql/spi/block/SingleArrayBlockWriter.java/SingleArrayBlockWriter/appendStructureInternal
class SingleArrayBlockWriter:    @Override
    public BlockBuilder appendStructureInternal(Block block, int position)
    {
        blockBuilder.appendStructureInternal(block, position);
        entryAdded();
        return this;
    }