minor: clarify docstring on DictionaryArray::lookup_key (#1910)

* minor: clarify docstring on `DictionaryArray::lookup_key` * Update arrow/src/array/array_dictionary.rs Co-authored-by: Liang-Chi Hsieh <viirya@gmail.com> Co-authored-by: Liang-Chi Hsieh <viirya@gmail.com>
apache · Jun 21, 2022 · aee2628 · aee2628
1 parent 12ac5c7
commit aee2628
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/arrow/src/array/array_dictionary.rs b/arrow/src/array/array_dictionary.rs
@@ -128,7 +128,11 @@ impl<'a, K: ArrowPrimitiveType> DictionaryArray<K> {
         &self.keys
     }
 
-    /// Returns the lookup key by doing reverse dictionary lookup
+    /// If `value` is present in `values` (aka the dictionary),
+    /// returns the corresponding key (index into the `values`
+    /// array). Otherwise returns `None`.
+    ///
+    /// Panics if `values` is not a [`StringArray`].
     pub fn lookup_key(&self, value: &str) -> Option<K::Native> {
         let rd_buf: &StringArray =
             self.values.as_any().downcast_ref::<StringArray>().unwrap();