presto-main/src/main/java/io/prestosql/operator/unnest/ArrayOfRowsUnnester.java/ArrayOfRowsUnnester/processCurrentPosition
class ArrayOfRowsUnnester:    @Override
    public void processCurrentPosition(int requireCount)
    {
        // Translate to row block index
        int rowBlockIndex = columnarArray.getOffset(getCurrentPosition());

        // Unnest current entry
        for (int i = 0; i < getCurrentUnnestedLength(); i++) {
            if (columnarRow.isNull(rowBlockIndex + i)) {
                // Nulls have to be appended when Row element itself is null
                for (int field = 0; field < fieldCount; field++) {
                    getBlockBuilder(field).appendNull();
                }
                nullRowsEncountered++;
            }
            else {
                for (int field = 0; field < fieldCount; field++) {
                    getBlockBuilder(field).appendElement(rowBlockIndex + i - nullRowsEncountered);
                }
            }
        }

        // Append nulls if more output entries are needed
        appendNulls(requireCount - getCurrentUnnestedLength());
    }