データ数の制限

Firebaseコレクションには、膨大な量のデータが含まれる場合があります。 必要なデータのみを絞り込んで取得すると、アプリケーションをより効率的にしてデータ通信量やサービス料金を下げることができます。

Collectionオブジェクトに読み込まれるデータの量を制限するには、3つの簡単な方法があります。

  • fieldsプロパティを使用して、読み込むフィールドを指定します。
  • pageSizeプロパティを妥当なレコード数に設定し、pageOnServerプロパティをtrueに設定します。
  • queryFilterプロパティを、データに適用するフィルターを記述するオブジェクトに設定します。

このサンプルは、これらすべての手法を示しています。

import 'bootstrap.css'; import '@grapecity/wijmo.styles/wijmo.css'; import './styles.css'; import { Firestore, Collection } from '@grapecity/wijmo.cloud'; import { ComboBox, CollectionViewNavigator } from '@grapecity/wijmo.input'; import { FlexGrid } from '@grapecity/wijmo.grid'; document.readyState === 'complete' ? init() : window.onload = init; function init() { // create the Firestore data source const API_KEY = 'AIzaSyDh6pPihWP4gpnlvhuL_4DrRhqRSBhKRS4'; const PROJECT_ID = 'wijmo-867c8'; const fireStore = new Firestore(PROJECT_ID, API_KEY); // load the Customers collection (selected fields, server-side paging) const countries = '東京都,神奈川県,大阪府,北海道,宮城県'.split(','); const customers = new Collection(fireStore, 'Customers', { sortDescriptions: ['CustomerID'], fields: [ 'CustomerID', 'CompanyName', 'ContactName', 'City', 'Country' ], pageSize: 6, pageOnServer: true }).where('Country', '==', countries[0]); // filter the Collection by country new ComboBox('#cmbCountries', { itemsSource: countries, textChanged: (s, e) => { customers.where('Country', '==', s.text); customers.moveToFirstPage(); } }); // navigate the Collection by page new CollectionViewNavigator('#fsCustomerPager', { cv: customers, byPage: true, headerFormat: '{current:n0} ページ' }); // show the filtered/paged customers new FlexGrid('#fsCustomerGrid', { selectionMode: 'MultiRange', showMarquee: true, isReadOnly: true, autoGenerateColumns: false, columns: [ { binding: 'CustomerID', header: '取引先ID' }, { binding: 'CompanyName', header: '取引先名', width: 200 }, { binding: 'ContactName', header: '担当者名', width: 150 }, { binding: 'City', header: '市区町村' }, { binding: 'Country', header: '都道府県' }, ], itemsSource: customers }); }
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>GrapeCity Wijmo Firestore Data Limits</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <!-- SystemJS --> <script src="node_modules/systemjs/dist/system.src.js"></script> <script src="systemjs.config.js"></script> <script> System.import('./src/app'); </script> </head> <body> <div class="container-fluid"> <div id="cmbCountries"></div> <div id="fsCustomerPager"></div> <div id="fsCustomerGrid"></div> </div> </body> </html>
.wj-flexgrid { margin: 1em 0; } .wj-combobox { margin-right: 1em; }
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