From dbd1fdd96290e5aa6453b558ba73d818f159523f Mon Sep 17 00:00:00 2001
From: Raz Luvaton <16746759+rluvaton@users.noreply.github.com>
Date: Fri, 13 Dec 2024 00:00:06 +0200
Subject: [PATCH] adding comment

---
 arrow-array/src/builder/generic_bytes_dictionary_builder.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arrow-array/src/builder/generic_bytes_dictionary_builder.rs b/arrow-array/src/builder/generic_bytes_dictionary_builder.rs
index 8d90339642ad..6bc4c0a48d35 100644
--- a/arrow-array/src/builder/generic_bytes_dictionary_builder.rs
+++ b/arrow-array/src/builder/generic_bytes_dictionary_builder.rs
@@ -307,7 +307,9 @@ where
 
     /// Extends builder with dictionary
     ///
-    /// This is the same as `extends` but avoid lookup for each item in the iterator 
+    /// This is the same as `extends` but avoid lookup for each item in the iterator
+    ///
+    /// when dictionary values are null (the actual mapped values) the keys are null
     ///
     pub fn extend_dictionary(&mut self, dictionary: &TypedDictionaryArray<K, GenericByteArray<T>>) -> Result<(), ArrowError> {
         let values = dictionary.values();