[GitHub] [arrow-rs] tustvold commented on a diff in pull request #1893: Correct nullable in read_dictionary

[GitBox]

tustvold commented on code in PR #1893:
URL: https://github.com/apache/arrow-rs/pull/1893#discussion_r899782342


##########
arrow/src/ipc/reader.rs:
##########
@@ -702,7 +702,11 @@ pub fn read_dictionary(
         DataType::Dictionary(_, ref value_type) => {
             // Make a fake schema for the dictionary batch.
             let schema = Schema {
-                fields: vec![Field::new("", value_type.as_ref().clone(), 
false)],
+                fields: vec![Field::new(
+                    "",
+                    value_type.as_ref().clone(),
+                    first_field.is_nullable(),

Review Comment:
   Could you expand a bit on what is going on here and why? Whilst dictionary 
values can contain nulls, this and the null count describe the nullability of 
the values not the keys.
   
   I'm basically a little confused what this record batch actually is, and why 
it isn't just an ArrarRef...



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