tustvold commented on issue #4408:
URL: https://github.com/apache/arrow-rs/issues/4408#issuecomment-1589678323

   A MapArray is a stored using the [variable sized list 
layout](https://arrow.apache.org/docs/format/Columnar.html#variable-size-list-layout).
 As such it has an offsets buffer that determines the length of its children.
   
   So in your example to access the value you could either use `MapArray::value`
   
   ```
   let v = map.value(0);
   assert_eq!(v.len(), 1);
   
   let keys = v.column(0).as_primitive::<UInt32Type>();
   let values = v.column(1).as_primitive::<UInt32Type>();
   
   assert_eq!(keys.value(0), values.value(0));
   assert_eq!(keys.value(0), SLICE_OFFSET as u32);
   ```
   
   Or you can access the underlying arrays directly, using `value_offsets`, and 
apply this to `MapArray::keys` and `MapArray::values`
   
   
   
   


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