[GitHub] [arrow-rs] tustvold commented on a diff in pull request #3080: early type checks in `RowConverter`

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

tustvold commented on code in PR #3080:
URL: https://github.com/apache/arrow-rs/pull/3080#discussion_r1019551725


##########
arrow/src/row/mod.rs:
##########
@@ -229,14 +229,70 @@ impl SortField {
     }
 }
 
+/// Helper that is used for [`downcast_primitive`] and just returns `true`.
+macro_rules! always_true {
+    ($t:ty) => {
+        true
+    };
+}
+
 impl RowConverter {
     /// Create a new [`RowConverter`] with the provided schema
-    pub fn new(fields: Vec<SortField>) -> Self {
+    pub fn new(fields: Vec<SortField>) -> Result<Self> {
+        if !Self::supports_fields(&fields) {
+            return Err(ArrowError::NotYetImplemented(format!(
+                "not yet implemented: {:?}",
+                fields
+            )));
+        }
+
         let interners = (0..fields.len()).map(|_| None).collect();
-        Self {
+        Ok(Self {
             fields: fields.into(),
             interners,
+        })
+    }
+
+    /// Check if the given fields are supported by the row format.
+    pub fn supports_fields(fields: &[SortField]) -> bool {
+        for f in fields {
+            let data_type = &f.data_type;

Review Comment:
   I think this can be simplified to something like
   
   ```
   match data_type {
       DataType::Dictionary(_, v) => !DataType::is_nested(v.as_ref()),
       _ => !DataType::is_nested(data_type),
   }
   ```



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