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Author: wu-hui

firebase-firestore/src/main/java/com/google/firebase/firestore/local/LocalDocumentsView.java

@@ -158,12 +158,8 @@ private Map<DocumentKey, OverlayedDocument> computeViews(
       Set<DocumentKey> existenceStateChanged) {
     Map<DocumentKey, MutableDocument> recalculateDocuments = new HashMap<>();
     Map<DocumentKey, FieldMask> mutatedFields = new HashMap<>();
-    Set<DocumentKey> keysWithOverlay = new HashSet<>();
     for (MutableDocument doc : docs.values()) {
       Overlay overlay = overlays.get(doc.getKey());
-      if (overlay != null) {
-        keysWithOverlay.add(doc.getKey());
-      }
 
       // Recalculate an overlay if the document's existence state is changed due to a remote
       // event *and* the overlay is a PatchMutation. This is because document existence state
@@ -179,6 +175,9 @@ private Map<DocumentKey, OverlayedDocument> computeViews(
         overlay
             .getMutation()
             .applyToLocalView(doc, overlay.getMutation().getFieldMask(), Timestamp.now());
+      } else { // overlay == null
+        // Using EMPTY to indicate there is no overlay for the document.
+        mutatedFields.put(doc.getKey(), FieldMask.EMPTY);
       }
     }
 
@@ -190,10 +189,7 @@ private Map<DocumentKey, OverlayedDocument> computeViews(
     for (Map.Entry<DocumentKey, MutableDocument> entry : docs.entrySet()) {
       result.put(
           entry.getKey(),
-          new OverlayedDocument(
-              entry.getValue(),
-              keysWithOverlay.contains(entry.getKey()),
-              mutatedFields.get(entry.getKey())));
+          new OverlayedDocument(entry.getValue(), mutatedFields.get(entry.getKey())));
     }
     return result;
   }

firebase-firestore/src/main/java/com/google/firebase/firestore/local/OverlayedDocument.java

@@ -21,13 +21,11 @@
 /** Represents a local view (overlay) of a document, and the fields that are locally mutated. */
 public class OverlayedDocument {
   private Document overlayedDocument;
-  private FieldMask mutatedFields;
-  private boolean hasOverlay;
+  @Nullable private FieldMask mutatedFields;
 
-  OverlayedDocument(Document overlayedDocument, boolean hasOverlay, FieldMask mutatedFields) {
+  OverlayedDocument(Document overlayedDocument, FieldMask mutatedFields) {
     this.overlayedDocument = overlayedDocument;
     this.mutatedFields = mutatedFields;
-    this.hasOverlay = hasOverlay;
   }
 
   public Document getDocument() {
@@ -37,12 +35,13 @@ public Document getDocument() {
   /**
    * The fields that are locally mutated by patch mutations.
    *
-   * <p>If hasOverlay() is true and the overlayed document is from set or delete mutations, this
-   * returns null. If hasOverlay() is false, this returns FieldMask.EMPTY.
+   * <p>If the overlayed document is from set or delete mutations, returns null.
+   *
+   * <p>If there is no overlay (mutation) for the document, returns FieldMask.EMPTY.
    */
   // TODO(b/262245989): This screams for a proper sum type (Tagged Union) which does not exist in
   // Java (yet).
   public @Nullable FieldMask getMutatedFields() {
-    return hasOverlay ? mutatedFields : FieldMask.EMPTY;
+    return mutatedFields;
   }
 }