[GitHub] [arrow-datafusion] alamb commented on a diff in pull request #6366: Concurrent Parquet Schema Inference

["alamb (via GitHub)" <gi...@apache.org>]

alamb commented on code in PR #6366:
URL: https://github.com/apache/arrow-datafusion/pull/6366#discussion_r1196982227


##########
datafusion/core/src/datasource/file_format/parquet.rs:
##########
@@ -151,12 +152,12 @@ impl FileFormat for ParquetFormat {
         store: &Arc<dyn ObjectStore>,
         objects: &[ObjectMeta],
     ) -> Result<SchemaRef> {
-        let mut schemas = Vec::with_capacity(objects.len());
-        for object in objects {
-            let schema =
-                fetch_schema(store.as_ref(), object, self.metadata_size_hint).await?;
-            schemas.push(schema)
-        }
+        let schemas: Vec<_> = futures::stream::iter(objects)
+            .map(|object| fetch_schema(store.as_ref(), object, self.metadata_size_hint))
+            .boxed() // Workaround https://github.com/rust-lang/rust/issues/64552

Review Comment:
   I found using streams was a similarly frustrating experience where the compiler give you an opaque error message (and opaque is being polite)
   



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