fix(firestore): use recursive delete for collection

samples/snippets/pom.xml

@@ -34,7 +34,7 @@
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>libraries-bom</artifactId>
-        <version>26.65.0</version>
+        <version>26.75.0</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>

samples/snippets/src/main/java/com/example/firestore/snippets/ManageDataSnippets.java

@@ -24,7 +24,6 @@
 import com.google.cloud.firestore.FieldValue;
 import com.google.cloud.firestore.Firestore;
 import com.google.cloud.firestore.Query;
-import com.google.cloud.firestore.QueryDocumentSnapshot;
 import com.google.cloud.firestore.QuerySnapshot;
 import com.google.cloud.firestore.SetOptions;
 import com.google.cloud.firestore.TransactionOptions;
@@ -304,27 +303,16 @@ void deleteDocument() throws Exception {
   }
 
   // [START firestore_data_delete_collection]
-  /**
-   * Delete a collection in batches to avoid out-of-memory errors. Batch size may be tuned based on
-   * document size (atmost 1MB) and application requirements.
-   */
-  void deleteCollection(CollectionReference collection, int batchSize) {
+  /** Delete a collection and all its subcollections. */
+  void deleteCollection(CollectionReference collection) {
+    Firestore db = collection.getFirestore();
+
+    ApiFuture<Void> future = db.recursiveDelete(collection);
     try {
-      // retrieve a small batch of documents to avoid out-of-memory errors
-      ApiFuture<QuerySnapshot> future = collection.limit(batchSize).get();
-      int deleted = 0;
-      // future.get() blocks on document retrieval
-      List<QueryDocumentSnapshot> documents = future.get().getDocuments();
-      for (QueryDocumentSnapshot document : documents) {
-        document.getReference().delete();
-        ++deleted;
-      }
-      if (deleted >= batchSize) {
-        // retrieve and delete another batch
-        deleteCollection(collection, batchSize);
-      }
+      future.get();
+      System.out.println("Collection and all its subcollections deleted successfully.");
     } catch (Exception e) {
-      System.err.println("Error deleting collection : " + e.getMessage());
+      System.err.println("Error deleting collection recursively : " + e.getMessage());
     }
   }
 

samples/snippets/src/test/java/com/example/firestore/BaseIntegrationTest.java

@@ -83,6 +83,16 @@ protected static void deleteAllDocuments(Firestore db) throws Exception {
     }
   }
 
+  protected static void deleteCollection(Firestore db, String collectionName) throws Exception {
+    ApiFuture<Void> future = db.recursiveDelete(db.collection(collectionName));
+    try {
+      future.get();
+      System.out.println("Collection and all its subcollections deleted successfully.");
+    } catch (Exception e) {
+      System.err.println("Error deleting collection recursively : " + e.getMessage());
+    }
+  }
+
   @AfterClass
   public static void tearDownAfterClass() throws Exception {
     db.close();

samples/snippets/src/test/java/com/example/firestore/snippets/ManageDataSnippetsIT.java

@@ -26,6 +26,9 @@
 import com.google.cloud.firestore.CollectionReference;
 import com.google.cloud.firestore.DocumentReference;
 import com.google.cloud.firestore.DocumentSnapshot;
+import com.google.cloud.firestore.QuerySnapshot;
+import com.google.cloud.firestore.WriteResult;
+
 import java.util.Date;
 import java.util.Map;
 import java.util.Objects;
@@ -152,6 +155,23 @@ public void testDeleteDocument() throws Exception {
     getDocumentDataAsMap(db.collection("cities").document("DC"));
   }
 
+  @Test
+  public void testDeleteCollection() throws Exception {
+    // Create collection and document to be deleted
+    Map<String, Object> docData = Map.of("name", "Los Angeles");
+    ApiFuture<WriteResult> future = db.collection("usa-cities").document("LA").set(docData);
+    future.get();
+
+    // Delete collection
+    manageDataSnippets.deleteCollection(db.collection("usa-cities"));
+
+    // Verify collection is deleted by trying to read from it
+    CollectionReference collectionReference = db.collection("usa-cities");
+    collectionReference.limit(1);
+    QuerySnapshot snapshot = collectionReference.get().get();
+    assertTrue(snapshot.isEmpty());
+  }
+
   @Test
   public void testSimpleTransaction() throws Exception {
     DocumentReference docRef = db.collection("cities").document("SF");
@@ -208,8 +228,8 @@ public void testSnapshotReads() throws Exception {
 
   @AfterClass
   public static void tearDown() throws Exception {
-    manageDataSnippets.deleteCollection(db.collection("cities"), 10);
-    manageDataSnippets.deleteCollection(db.collection("users"), 10);
+    deleteCollection(db, "cities");
+    deleteCollection(db, "users");
     manageDataSnippets.close();
   }
 }