Changelog for FieldValue change
-# Unreleased (21.4.0)
+# Unreleased
+- [changed] Changed the in-memory representation of Firestore documents to
+ reduce memory allocations and improve performance. Calls to
+ `DocumentSnapshot.getData()` and `DocumentSnapshot.toObject()` will see
+ the biggest improvement.
+
+# 21.4.0
- [feature] Firestore previously required that every document read in a
transaction must also be written. This requirement has been removed, and
you can now read a document in a transaction without writing to it.
