Limit Data

Firebase collections may contain huge amounts of data. Narrowing down and getting only the data you need makes applications more efficient and less expensive (cloud services are not always free).

There are three simple ways to limit the amount of data loaded into Collection objects:

  • Use the fields property to specify the fields you want to load.
  • Set the pageSize property to a reasonable number of records set the pageOnServer property to true.
  • Set the queryFilter property to an object that describes a filter to apply to the data.

This sample demonstrates all of these techniques.

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 = 'AIzaSyCvuXEzP57I5CQ9ifZDG2_K8M3nDa1LOPE'; const PROJECT_ID = 'test-9c0be'; const fireStore = new Firestore(PROJECT_ID, API_KEY); // load the Customers collection (selected fields, server-side paging) const countries = 'Brazil,France,Germany,UK,USA'.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: 'Page {current:n0}' }); // show the filtered/paged customers new FlexGrid('#fsCustomerGrid', { selectionMode: 'MultiRange', showMarquee: true, isReadOnly: true, autoGenerateColumns: false, columns: customers.fields.map(fld => { return { binding: fld }; }), 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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