Limit Data (Angular)

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.

Learn about FlexGrid | Limit Data Documentation | Cloud API Reference

This example uses Angular.

import 'bootstrap.css'; import '@mescius/wijmo.styles/wijmo.css'; import './styles.css'; // import '@angular/compiler'; import { Component, enableProdMode, ɵresolveComponentResources } from '@angular/core'; import { BrowserModule, bootstrapApplication } from '@angular/platform-browser'; import { FormsModule } from '@angular/forms'; // import { Firestore, Collection } from '@mescius/wijmo.cloud'; import { ComboBox } from '@mescius/wijmo.input'; import { WjInputModule } from '@mescius/wijmo.angular2.input'; import { WjGridModule } from '@mescius/wijmo.angular2.grid'; // @Component({ standalone: true, imports: [WjInputModule, WjGridModule, BrowserModule, FormsModule], selector: 'app-component', templateUrl: 'src/app.component.html', }) export class AppComponent { customers: Collection; countries: string[]; constructor() { // create the Firestore data source const API_KEY = 'AIzaSyBeEwDqO_h1KOMRekRrDizOZweSiTXRj2Y'; const PROJECT_ID = 'test-9c0be'; const fireStore = new Firestore(PROJECT_ID, API_KEY); // countries to filter by this.countries = 'Brazil,France,Germany,UK,USA'.split(','); // load the Customers collection (selected fields, server-side paging) this.customers = new Collection(fireStore, 'Customers', { sortDescriptions: ['CustomerID'], fields: ['CustomerID', 'CompanyName', 'ContactName', 'City', 'Country'], pageSize: 6, pageOnServer: true, }).where('Country', '==', this.countries[0]); } // update filter when selected country changes countryChanged(countryCombo: ComboBox) { this.customers.where('Country', '==', countryCombo.text); this.customers.moveToFirstPage(); } } // // enableProdMode(); // Resolve resources (templateUrl, styleUrls etc), After resolution all URLs have been converted into `template` strings. ɵresolveComponentResources(fetch).then(() => { // Bootstrap application bootstrapApplication(AppComponent).catch((err) => console.error(err)); });
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>MESCIUS Wijmo Firestore Data Limits</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <!-- Polyfills --> <script src="node_modules/core-js/client/shim.min.js"></script> <script src="node_modules/zone.js/fesm2015/zone.min.js"></script> <!-- SystemJS --> <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.21.5/system.src.js" integrity="sha512-skZbMyvYdNoZfLmiGn5ii6KmklM82rYX2uWctBhzaXPxJgiv4XBwJnFGr5k8s+6tE1pcR1nuTKghozJHyzMcoA==" crossorigin="anonymous"></script> <script src="systemjs.config.js"></script> <script> // workaround to load 'rxjs/operators' from the rxjs bundle System.import('rxjs').then(function (m) { System.set(SystemJS.resolveSync('rxjs/operators'), System.newModule(m.operators)); System.import('./src/app.component'); }); </script> </head> <body> <app-component></app-component> </body> </html>
<div class="container-fluid"> <wj-combo-box #countryCombo [itemsSource]="countries" (textChanged)="countryChanged(countryCombo)"> </wj-combo-box> <wj-collection-view-navigator [cv]="customers" [byPage]="true" headerFormat="Page {current:n0}"> </wj-collection-view-navigator> <wj-flex-grid selectionMode="MultiRange" [showMarquee]="true" [isReadOnly]="true" [itemsSource]="customers"> <wj-flex-grid-column binding="CustomerID" header="Customer ID"></wj-flex-grid-column> <wj-flex-grid-column binding="CompanyName" header="Company Name" [width]="200"></wj-flex-grid-column> <wj-flex-grid-column binding="ContactName" header="Contact Name" [width]="150"></wj-flex-grid-column> <wj-flex-grid-column binding="City"></wj-flex-grid-column> <wj-flex-grid-column binding="Country"></wj-flex-grid-column> </wj-flex-grid> </div>
.wj-flexgrid { margin: 1em 0; } .wj-combobox { margin-right: 1em; }
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'@angular/router': 'npm:@angular/router/fesm2022/router.mjs', '@angular/forms': 'npm:@angular/forms/fesm2022/forms.mjs', }, // packages tells the System loader how to load when no filename and/or no extension packages: { "./src": { defaultExtension: 'ts' }, "node_modules": { defaultExtension: 'js' }, wijmo: { defaultExtension: 'js', } } }); })(this);