aggregate.ts

/**
 * @license
 * 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.
 */

import { Query } from '../api';
import { firestoreClientRunCountQuery } from '../core/firestore_client';
import {
  AggregateField,
  AggregateQuerySnapshot
} from '../lite-api/aggregate_types';
import { cast } from '../util/input_validation';

import { ensureFirestoreConfigured, Firestore } from './database';
import { ExpUserDataWriter } from './reference_impl';

export { aggregateQuerySnapshotEqual } from '../lite-api/aggregate';

/**
 * Calculates the number of documents in the result set of the given query,
 * without actually downloading the documents.
 *
 * Using this function to count the documents is efficient because only the
 * final count, not the documents' data, is downloaded. This function can even
 * count the documents if the result set would be prohibitively large to
 * download entirely (e.g. thousands of documents).
 *
 * The result received from the server is presented, unaltered, without
 * considering any local state. That is, documents in the local cache are not
 * taken into consideration, neither are local modifications not yet
 * synchronized with the server. Previously-downloaded results, if any, are not
 * used: every request using this source necessarily involves a round trip to
 * the server.
 *
 * @param query - The query whose result set size to calculate.
 * @returns A Promise that will be resolved with the count; the count can be
 * retrieved from `snapshot.data().count`, where `snapshot` is the
 * `AggregateQuerySnapshot` to which the returned Promise resolves.
 */
export function getCountFromServer(
  query: Query<unknown>
): Promise<AggregateQuerySnapshot<{ count: AggregateField<number> }>> {
  const firestore = cast(query.firestore, Firestore);
  const client = ensureFirestoreConfigured(firestore);
  const userDataWriter = new ExpUserDataWriter(firestore);
  return firestoreClientRunCountQuery(client, query, userDataWriter);
}