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new 842de75bad Add `Metadata` `Arc` helper methods (#10693)
842de75bad is described below
commit 842de75bad77de1c530bf0e33ff742a3d33a9b67
Author: RIchard Baah <[email protected]>
AuthorDate: Tue Aug 18 12:30:01 2026 -0400
Add `Metadata` `Arc` helper methods (#10693)
# Which issue does this PR close?
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- Closes #10684.
# Rationale for this change
see #10684
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# What changes are included in this PR?
two new method
- `as_arc(&self) : Option<&Arc<BTreeMap<String, String>>>` returns a
reference to the inner Arc (or None for empty).
- `into_arc(self) :Option<Arc<BTreeMap<String, String>>>` consumes self
and hands back the Arc directly, enabling zero-copy conversions
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# Are these changes tested?
yes
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# Are there any user-facing changes?
yes, new public methods `as_arc` & `into_arc` on Metadata.
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---
arrow-schema/src/metadata.rs | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)
diff --git a/arrow-schema/src/metadata.rs b/arrow-schema/src/metadata.rs
index 7b9ec707c7..38cd811910 100644
--- a/arrow-schema/src/metadata.rs
+++ b/arrow-schema/src/metadata.rs
@@ -128,6 +128,22 @@ impl Metadata {
self.0 = None;
}
+ /// Returns a reference to the underlying [`Arc`], or `None` if the map is
empty.
+ ///
+ /// Useful for pointer-based deduplication (e.g. memory accounting) where
+ /// callers need to detect clones that share the same allocation.
+ pub fn as_arc(&self) -> Option<&Arc<BTreeMap<String, String>>> {
+ self.0.as_ref()
+ }
+
+ /// Consumes `self` and returns the underlying [`Arc`], or `None` if the
map is empty.
+ ///
+ /// Useful for zero-copy conversion into wrapper types that also store an
+ /// `Arc<BTreeMap<String, String>>` internally.
+ pub fn into_arc(self) -> Option<Arc<BTreeMap<String, String>>> {
+ self.0
+ }
+
/// Returns an iterator over the entries, sorted by key.
pub fn iter(&self) -> MetadataIter<'_> {
self.0
@@ -439,6 +455,30 @@ mod tests {
assert!(clone.is_empty());
}
+ #[test]
+ fn test_as_arc_into_arc() {
+ let empty = Metadata::new();
+ assert!(empty.as_arc().is_none());
+ assert!(empty.into_arc().is_none());
+
+ // Non-empty metadata exposes the same Arc via as_arc / into_arc
+ let metadata = Metadata::from([("a", "1")]);
+ let arc_ref = metadata.as_arc().expect("non-empty");
+ assert_eq!(arc_ref.get("a").map(String::as_str), Some("1"));
+
+ let clone = metadata.clone();
+ // Clones share the same allocation
+ assert!(Arc::ptr_eq(
+ metadata.as_arc().unwrap(),
+ clone.as_arc().unwrap()
+ ));
+
+ let arc = metadata.into_arc().expect("non-empty");
+ assert_eq!(arc.get("a").map(String::as_str), Some("1"));
+ // into_arc gives back the same Arc (no copy)
+ assert!(Arc::ptr_eq(&arc, clone.as_arc().unwrap()));
+ }
+
#[test]
fn test_debug() {
let metadata = Metadata::from([("b", "2"), ("a", "1")]);
