[GitHub] [arrow-rs] tustvold commented on issue #3589: Nullif of NULL Predicate is not NULL

["tustvold (via GitHub)" <gi...@apache.org>]

tustvold commented on issue #3589:
URL: https://github.com/apache/arrow-rs/issues/3589#issuecomment-1400913675

   Looking at how this is typically used I realise the current logic is correct. In particular the common pattern is
   
   ```
   let cond_array = eq_dyn(lhs, rhs)?;
   // Now, invoke nullif on the result
   let array = nullif(lhs, as_boolean_array(&cond_array)?)?;
   ```
   
   In particular if `lhs` or `rhs` is null, `cond_array` will also be null.
   
   The result should only be `null` if `lhs` is null, which is the case if `NULL` passed to `nullif` preserves the nullability of `lhs` in the event of `rhs` being null.


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