alamb commented on issue #4840:
URL: https://github.com/apache/arrow-rs/issues/4840#issuecomment-1908150493

   > Physical and logical null are truly confusing. 
   
   I agree @waynexia 
   
   I don't quite follow your examples with 4 different types of null. 
   
   If you need to quickly create an array that represents entirely null of a 
single type, there is 
[`new_null_array`](https://docs.rs/arrow/latest/arrow/array/fn.new_null_array.html),
 but as you seem to imply that certainly results in a larger array than 
strictly necessary
   
   It is fast to check for an array that contains only nulls by using  
[`Array::nulls`](https://docs.rs/arrow/latest/arrow/array/trait.Array.html#tymethod.nulls)
 I think like:
   
   ```rust
   let num_nulls = array.nulls().map(|nulls| nulls.null_count()).unwrap_or(0)
   let is_all_null = num_nulls = array.len();
   ```
   
   Though as the docs say, this isn't correct for Dictionary or REE arrays
   
   
   


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