COUNT API proposal

firebase-firestore/ktx/src/test/kotlin/com/google/firebase/firestore/ktx/FirestoreTests.kt

@@ -18,11 +18,8 @@ import androidx.test.core.app.ApplicationProvider
 import com.google.common.truth.Truth.assertThat
 import com.google.firebase.FirebaseApp
 import com.google.firebase.FirebaseOptions
-import com.google.firebase.firestore.DocumentSnapshot
-import com.google.firebase.firestore.FieldPath
-import com.google.firebase.firestore.FirebaseFirestore
-import com.google.firebase.firestore.FirebaseFirestoreSettings
-import com.google.firebase.firestore.TestUtil
+import com.google.firebase.firestore.*
+import com.google.firebase.firestore.AggregateSource.SERVER_DIRECT
 import com.google.firebase.firestore.model.ObjectValue
 import com.google.firebase.firestore.testutil.TestUtil.wrap
 import com.google.firebase.ktx.Firebase
@@ -41,6 +38,37 @@ const val API_KEY = "API_KEY"
 
 const val EXISTING_APP = "existing"
 
+class AggregateDemo {
+
+  fun Demo0_NormalQuery(db: FirebaseFirestore) {
+    val query = db.collection("games/halo/players")
+    val snapshot = query.get().result
+    assertThat(snapshot.size()).isEqualTo(5_000_000)
+  }
+
+  fun Demo1_CountOfDocumentsInACollection(db: FirebaseFirestore) {
+    val countQuery = db.collection("games/halo/players").count()
+    val snapshot = countQuery.get(SERVER_DIRECT).result
+    assertThat(snapshot.count).isEqualTo(5_000_000)
+  }
+
+  fun Demo2_CountOfDocumentsInACollectionWithFilter(db: FirebaseFirestore) {
+    val query = db.collection("games/halo/players").whereEqualTo("online", true)
+    val countQuery = query.count()
+    val snapshot = countQuery.get(SERVER_DIRECT).result
+    assertThat(snapshot.count).isEqualTo(2000)
+  }
+
+  fun Demo3_CountOfDocumentsInACollectionWithLimit(db: FirebaseFirestore) {
+    val query = db.collection("games/halo/players").limit(9000)
+    val countQuery = query.count()
+    val snapshot = countQuery.get(SERVER_DIRECT).result
+    assertThat(snapshot.count).isEqualTo(9000)
+  }
+
+}
+
+
 abstract class BaseTestCase {
     @Before
     fun setUp() {

firebase-firestore/src/main/java/com/google/firebase/firestore/AggregateDemo.java

@@ -0,0 +1,48 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.firebase.firestore;
+
+final class AggregateDemo {
+
+  private AggregateDemo() {}
+
+  public void Demo0_NormalQuery(FirebaseFirestore db) {
+    CollectionReference query = db.collection("games/halo/players");
+    QuerySnapshot snapshot = query.get().getResult();
+    assertEqual(snapshot.size(), 5_000_000);
+  }
+
+  public void Demo1_CountOfDocumentsInACollection(FirebaseFirestore db) {
+    AggregateQuery countQuery = db.collection("games/halo/players").count();
+    AggregateQuerySnapshot snapshot = countQuery.get(AggregateSource.SERVER_DIRECT).getResult();
+    assertEqual(snapshot.getCount(), 5_000_000);
+  }
+
+  public void Demo2_CountOfDocumentsInACollectionWithFilter(FirebaseFirestore db) {
+    Query query = db.collection("games/halo/players").whereEqualTo("online", true);
+    AggregateQuery countQuery = query.count();
+    AggregateQuerySnapshot snapshot = countQuery.get(AggregateSource.SERVER_DIRECT).getResult();
+    assertEqual(snapshot.getCount(), 2000);
+  }
+
+  public void Demo2_CountOfDocumentsInACollectionWithLimit(FirebaseFirestore db) {
+    Query query = db.collection("games/halo/players").limit(9000);
+    AggregateQuery countQuery = query.count();
+    AggregateQuerySnapshot snapshot = countQuery.get(AggregateSource.SERVER_DIRECT).getResult();
+    assertEqual(snapshot.getCount(), 9000);
+  }
+
+  private static void assertEqual(Object o1, Object o2) {}
+}

firebase-firestore/src/main/java/com/google/firebase/firestore/AggregateQuery.java

@@ -0,0 +1,43 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.firebase.firestore;
+
+import androidx.annotation.NonNull;
+import com.google.android.gms.tasks.Task;
+
+public class AggregateQuery {
+
+  AggregateQuery() {}
+
+  @NonNull
+  public Query getQuery() {
+    throw new RuntimeException("not implemented");
+  }
+
+  @NonNull
+  public Task<AggregateQuerySnapshot> get(@NonNull AggregateSource source) {
+    throw new RuntimeException("not implemented");
+  }
+
+  @Override
+  public int hashCode() {
+    throw new RuntimeException("not implemented");
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    throw new RuntimeException("not implemented");
+  }
+}

firebase-firestore/src/main/java/com/google/firebase/firestore/AggregateQuerySnapshot.java

@@ -0,0 +1,48 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.firebase.firestore;
+
+import androidx.annotation.Nullable;
+import javax.annotation.Nonnull;
+
+public class AggregateQuerySnapshot {
+
+  AggregateQuerySnapshot() {}
+
+  @Nonnull
+  public AggregateQuery getQuery() {
+    throw new RuntimeException("not implemented");
+  }
+
+  @Nullable
+  public Long getCount() {
+    throw new RuntimeException("not implemented");
+  }
+
+  @Override
+  public boolean equals(@Nullable Object obj) {
+    throw new RuntimeException("not implemented");
+  }
+
+  @Override
+  public int hashCode() {
+    throw new RuntimeException("not implemented");
+  }
+
+  @Override
+  public String toString() {
+    throw new RuntimeException("not implemented");
+  }
+}

firebase-firestore/src/main/java/com/google/firebase/firestore/AggregateSource.java

@@ -0,0 +1,19 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.firebase.firestore;
+
+public enum AggregateSource {
+  SERVER_DIRECT,
+}

firebase-firestore/src/main/java/com/google/firebase/firestore/Query.java

@@ -1223,6 +1223,11 @@ private void validateHasExplicitOrderByForLimitToLast() {
     }
   }
 
+  @NonNull
+  public AggregateQuery count() {
+    throw new RuntimeException("not implemented");
+  }
+
   @Override
   public boolean equals(Object o) {
     if (this == o) {