Re: [PR] Add documentation for UNION schema handling. [datafusion]

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

wiedld commented on code in PR #17248:
URL: https://github.com/apache/datafusion/pull/17248#discussion_r2286487449


##########
datafusion/expr/src/logical_plan/plan.rs:
##########
@@ -2896,16 +2899,7 @@ impl Union {
 fn intersect_maps<'a>(
     inputs: impl IntoIterator<Item = &'a HashMap<String, String>>,
 ) -> HashMap<String, String> {
-    let mut inputs = inputs.into_iter();
-    let mut merged: HashMap<String, String> = inputs.next().cloned().unwrap_or_default();
-    for input in inputs {
-        // The extra dereference below (`&*v`) is a workaround for https://github.com/rkyv/rkyv/issues/434.
-        // When this crate is used in a workspace that enables the `rkyv-64` feature in the `chrono` crate,
-        // this triggers a Rust compilation error:
-        // error[E0277]: can't compare `Option<&std::string::String>` with `Option<&mut std::string::String>`.
-        merged.retain(|k, v| input.get(k) == Some(&*v));
-    }
-    merged
+    intersect_for_union(inputs)

Review Comment:
   Note that at construction, we handle the schema by intersection.



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