[GitHub] [arrow] alamb commented on a change in pull request #8850: ARROW-10591: [Rust] Add support for StructArray to MutableArrayData

[GitBox <gi...@apache.org>]

alamb commented on a change in pull request #8850:
URL: https://github.com/apache/arrow/pull/8850#discussion_r537022972



##########
File path: rust/arrow/src/array/transform/mod.rs
##########
@@ -285,10 +288,16 @@ impl<'a> MutableArrayData<'a> {
     /// `use_nulls` is a flag used to optimize insertions. It should be `false` if the only source of nulls
     /// are the arrays themselves and `true` if the user plans to call [MutableArrayData::extend_nulls].
     /// In other words, if `use_nulls` is `false`, calling [MutableArrayData::extend_nulls] should not be used.
-    pub fn new(arrays: Vec<&'a ArrayData>, use_nulls: bool, capacity: usize) -> Self {
+    pub fn new(arrays: Vec<&'a ArrayData>, mut use_nulls: bool, capacity: usize) -> Self {

Review comment:
       https://github.com/apache/arrow/pull/8848 appears to contain this same code -- though github seems to think merging will not be a problem

##########
File path: rust/arrow/src/array/transform/mod.rs
##########
@@ -687,4 +728,118 @@ mod tests {
         let expected = Int16Array::from(vec![Some(1), None]);
         assert_eq!(result.keys(), &expected);
     }
+
+    #[test]
+    fn test_struct() {
+        let strings: ArrayRef = Arc::new(StringArray::from(vec![
+            Some("joe"),
+            None,
+            None,
+            Some("mark"),
+            Some("doe"),
+        ]));
+        let ints: ArrayRef = Arc::new(Int32Array::from(vec![
+            Some(1),
+            Some(2),
+            Some(3),
+            Some(4),
+            Some(5),
+        ]));
+
+        let array =
+            StructArray::try_from(vec![("f1", strings.clone()), ("f2", ints.clone())])
+                .unwrap()
+                .data();
+        let arrays = vec![array.as_ref()];
+        let mut mutable = MutableArrayData::new(arrays, false, 0);
+
+        mutable.extend(0, 1, 3);

Review comment:
       I wonder if ensuring the slice covers an actual string value would be useful (this slice just takes the two `None`, `None` values). It it it was like `mutable.extend(0, 2, 4)` that would also include `Some("mark")`. The same comment applies to `test_struct_nulls` as well




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