[GitHub] [arrow-rs] tustvold commented on a diff in pull request #2083: Add IPC truncation test case for StructArray

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

tustvold commented on code in PR #2083:
URL: https://github.com/apache/arrow-rs/pull/2083#discussion_r922407674


##########
arrow/src/ipc/writer.rs:
##########
@@ -1784,4 +1784,52 @@ mod tests {
 
         assert_eq!(record_batch_slice, deserialized_batch);
     }
+
+    #[test]
+    fn truncate_ipc_struct_array() {
+        fn create_batch() -> RecordBatch {
+            let strings: StringArray = [Some("foo"), None, Some("bar"), Some("baz")]
+                .into_iter()
+                .collect();
+            let ints: Int32Array =
+                [Some(0), Some(2), None, Some(1)].into_iter().collect();
+
+            let struct_array = StructArray::from(vec![
+                (
+                    Field::new("s", DataType::Utf8, true),
+                    Arc::new(strings) as ArrayRef,
+                ),
+                (
+                    Field::new("c", DataType::Int32, false),
+                    Arc::new(ints) as ArrayRef,
+                ),
+            ]);
+
+            let schema = Schema::new(vec![Field::new(
+                "struct_array",
+                struct_array.data_type().clone(),
+                true,
+            )]);
+
+            RecordBatch::try_new(Arc::new(schema), vec![Arc::new(struct_array)]).unwrap()
+        }
+
+        let record_batch = create_batch();
+        let record_batch_slice = record_batch.slice(1, 2);

Review Comment:
   There is currently an odd hack in Array::slice for StructArray that pushes down the offset to the child arrays. You will need to manually construct the ArrayData for the StructArray in order to properly test the case of a StructArray with a non-zero offset.



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