presto-main/src/main/java/io/prestosql/operator/unnest/UnnestBlockBuilder.java/UnnestBlockBuilder/appendId
class UnnestBlockBuilder:    private void appendId(int sourcePosition)
    {
        if (positionCount == ids.length) {
            // grow capacity
            int newSize = calculateNewArraySize(ids.length);
            ids = Arrays.copyOf(ids, newSize);
        }
        ids[positionCount] = sourcePosition;
        positionCount++;
    }