[GitHub] [arrow-rs] heyrutvik commented on a diff in pull request #2038: Implement FromIterator for Builders

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

heyrutvik commented on code in PR #2038:
URL: https://github.com/apache/arrow-rs/pull/2038#discussion_r918987650


##########
arrow/src/array/builder/decimal_builder.rs:
##########
@@ -149,20 +167,39 @@ impl ArrayBuilder for DecimalBuilder {
     fn into_box_any(self: Box<Self>) -> Box<dyn Any> {
         self
     }
+}
 
-    /// Returns the number of array slots in the builder
-    fn len(&self) -> usize {
-        self.builder.len()
-    }
-
-    /// Returns whether the number of array slots is zero
-    fn is_empty(&self) -> bool {
-        self.builder.is_empty()
-    }
+impl<Ptr: Borrow<Option<i128>>> FromIterator<Ptr> for DecimalBuilder {
+    fn from_iter<I: IntoIterator<Item = Ptr>>(iter: I) -> Self {
+        let iter = iter.into_iter();
+        let (lower, upper) = iter.size_hint();
+        let size_hint = upper.unwrap_or(lower);
+        let fixed_len = 16_usize;
+
+        let mut builder = FixedSizeListBuilder::with_capacity(

Review Comment:
   Ah, right. I was too focused on building builders out of its sub components. I totally forgot that builder contains handy methods to append values. It was fun experience though. 
   
   You will noticed this to almost all implementation (except one). I'll update the PR.  



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