[GitHub] [arrow] carols10cents commented on a change in pull request #8402: ARROW-8426: [Rust] [Parquet] - Add more support for converting Dicts

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

carols10cents commented on a change in pull request #8402:
URL: https://github.com/apache/arrow/pull/8402#discussion_r504931448



##########
File path: rust/parquet/src/arrow/converter.rs
##########
@@ -253,6 +256,34 @@ impl Converter<Vec<Option<ByteArray>>, LargeBinaryArray> for LargeBinaryArrayCon
     }
 }
 
+pub struct DictionaryArrayConverter {}
+
+impl<K: ArrowDictionaryKeyType> Converter<Vec<Option<ByteArray>>, DictionaryArray<K>>
+    for DictionaryArrayConverter
+{
+    fn convert(&self, source: Vec<Option<ByteArray>>) -> Result<DictionaryArray<K>> {
+        let data_size = source
+            .iter()
+            .map(|x| x.as_ref().map(|b| b.len()).unwrap_or(0))
+            .sum();
+
+        let keys_builder = PrimitiveBuilder::<K>::new(source.len());
+        let values_builder = StringBuilder::with_capacity(source.len(), data_size);
+
+        let mut builder = StringDictionaryBuilder::new(keys_builder, values_builder);
+        for v in source {
+            match v {
+                Some(array) => {
+                    builder.append(array.as_utf8()?)?;

Review comment:
       Do you mean make this one line again, like:
   
   `Some(array) => let _ = builder.append(array.as_utf8()?)?,`




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