[GitHub] [arrow] felipecrv opened a new issue, #35830: [C++] Handle only relevant slices of child arrays when hashing scalars from ListArrays

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

felipecrv opened a new issue, #35830:
URL: https://github.com/apache/arrow/issues/35830

   ### Describe the enhancement requested
   
   Issue is explained in the Python code below:
   
   ```python
   import pyarrow as pa
   
   a = pa.array([
       [{'a': 5}, {'a': 6}],
       [{'a': 7}, None]
   ])
   b = pa.array([
       [{'a': 7}, None]
   ])
   
   # a[1] and b[0] are represented as 2-element slices of a child array containing struct values
   # they start on different offsets, but obviously compare as equal
   assert a[1] == b[0]
   
   # logically equal values should hash to the same value, so when hashing the hashing
   # of the child array should start at the offset and not from 0 as it's done by default.
   hash1 = hash(a[1])
   hash2 = hash(b[0])
   assert hash1 == hash2
   ```
   
   #35814 fixes the bug for lists of structs, but the same bug might exist for other nested types:
   
   - [x] struct
   - [ ] sparse union
   - [ ] dense union
   - [ ] run-end encoded
   - [ ] more?
   
   ### Component(s)
   
   C++


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