[GitHub] [arrow] nevi-me commented on a change in pull request #9253: ARROW-11269: [Rust] [Parquet] Preserve timezone in int96 reader

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

nevi-me commented on a change in pull request #9253:
URL: https://github.com/apache/arrow/pull/9253#discussion_r559940749



##########
File path: rust/parquet/src/arrow/converter.rs
##########
@@ -168,19 +167,19 @@ impl Converter<Vec<Option<FixedLenByteArray>>, IntervalDayTimeArray>
     }
 }
 
-pub struct Int96ArrayConverter {}
+pub struct Int96ArrayConverter {
+    pub timezone: Option<String>,
+}
 
 impl Converter<Vec<Option<Int96>>, TimestampNanosecondArray> for Int96ArrayConverter {
     fn convert(&self, source: Vec<Option<Int96>>) -> Result<TimestampNanosecondArray> {
-        let mut builder = TimestampNanosecondBuilder::new(source.len());
-        for v in source {
-            match v {
-                Some(array) => builder.append_value(array.to_i64() * 1000000),
-                None => builder.append_null(),
-            }?
-        }
-
-        Ok(builder.finish())
+        Ok(TimestampNanosecondArray::from_opt_vec(

Review comment:
       We've found the builder pattern to be slower than allocating vecs. There's `FromIter` for PrimitiveArray, but no equivalent for `TimestampArray::from_opt_vec`. I've filed ARROW-11312 to address this.
   
   On the other field types, we don't use Array builder there, but use `ArrayData::builder(timestamp_with_timezone)`. So they don't suffer from the same limitation.




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