Fix docs unnecessarily undergo limbo resolution while resuming query bug

firebase-firestore/CHANGELOG.md

@@ -1,4 +1,5 @@
 # Unreleased
+* [fixed] Fixed an issue in the local cache synchronization logic where all locally-cached documents that matched a resumed query would be unnecessarily re-downloaded; with the fix it now only downloads the documents that are known to be out-of-sync. [#5506](//github.com/firebase/firebase-android-sdk/pull/5506)
 
 
 # 24.9.1

firebase-firestore/src/main/java/com/google/firebase/firestore/core/SyncEngine.java

@@ -653,7 +653,13 @@ private void emitNewSnapsAndNotifyLocalStore(
       }
       TargetChange targetChange =
           remoteEvent == null ? null : remoteEvent.getTargetChanges().get(queryView.getTargetId());
-      ViewChange viewChange = queryView.getView().applyChanges(viewDocChanges, targetChange);
+
+      boolean targetIsPendingReset =
+          remoteEvent != null
+              && remoteEvent.getTargetMismatches().get(queryView.getTargetId()) != null;
+
+      ViewChange viewChange =
+          queryView.getView().applyChanges(viewDocChanges, targetChange, targetIsPendingReset);
       updateTrackedLimboDocuments(viewChange.getLimboChanges(), queryView.getTargetId());
 
       if (viewChange.getSnapshot() != null) {

firebase-firestore/src/main/java/com/google/firebase/firestore/core/View.java

@@ -275,6 +275,21 @@ public ViewChange applyChanges(DocumentChanges docChanges) {
    * @return A new ViewChange with the given docs, changes, and sync state.
    */
   public ViewChange applyChanges(DocumentChanges docChanges, TargetChange targetChange) {
+    return applyChanges(docChanges, targetChange, false);
+  }
+
+  /**
+   * Updates the view with the given ViewDocumentChanges and updates limbo docs and sync state from
+   * the given (optional) target change.
+   *
+   * @param docChanges The set of changes to make to the view's docs.
+   * @param targetChange A target change to apply for computing limbo docs and sync state.
+   * @param targetIsPendingReset - Whether the target is pending to reset due to existence filter
+   *     mismatch. If not explicitly specified, it is treated equivalently to `false`.
+   * @return A new ViewChange with the given docs, changes, and sync state.
+   */
+  public ViewChange applyChanges(
+      DocumentChanges docChanges, TargetChange targetChange, boolean targetIsPendingReset) {
     hardAssert(!docChanges.needsRefill, "Cannot apply changes that need a refill");
 
     DocumentSet oldDocumentSet = documentSet;
@@ -293,8 +308,12 @@ public ViewChange applyChanges(DocumentChanges docChanges, TargetChange targetCh
           return query.comparator().compare(o1.getDocument(), o2.getDocument());
         });
     applyTargetChange(targetChange);
-    List<LimboDocumentChange> limboDocumentChanges = updateLimboDocuments();
-    boolean synced = limboDocuments.size() == 0 && current;
+    List<LimboDocumentChange> limboDocumentChanges =
+        targetIsPendingReset ? Collections.emptyList() : updateLimboDocuments();
+
+    // We are at synced state if there is no limbo docs are waiting to be resolved, view is current
+    // with the backend, and the query is not pending to reset due to existence filter mismatch.
+    boolean synced = limboDocuments.size() == 0 && current && !targetIsPendingReset;
     SyncState newSyncState = synced ? SyncState.SYNCED : SyncState.LOCAL;
     boolean syncStatedChanged = newSyncState != syncState;
     syncState = newSyncState;