Limit Data (React)

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 React.

import 'bootstrap.css'; import '@mescius/wijmo.styles/wijmo.css'; import ReactDOM from 'react-dom/client'; import React from 'react'; import useEvent from 'react-use-event-hook'; import { Firestore, Collection } from '@mescius/wijmo.cloud'; import { ComboBox, CollectionViewNavigator } from '@mescius/wijmo.react.input'; import { FlexGrid, FlexGridColumn } from '@mescius/wijmo.react.grid'; import './app.css'; const API_KEY = 'AIzaSyBeEwDqO_h1KOMRekRrDizOZweSiTXRj2Y'; const PROJECT_ID = 'test-9c0be'; const countries = ['Brazil', 'France', 'Germany', 'UK', 'USA']; const fireStore = new Firestore(PROJECT_ID, API_KEY); const customers = new Collection(fireStore, 'Customers', { sortDescriptions: ['CustomerID'], fields: [ 'CustomerID', 'CompanyName', 'ContactName', 'City', 'Country' ], pageSize: 6, pageOnServer: true }).where('Country', '==', countries[0]); function App() { // update filter when selected country changes const countryChanged = useEvent((countryCombo) => { customers.where('Country', '==', countryCombo.text); customers.moveToFirstPage(); }); return (<div className="container-fluid"> <ComboBox itemsSource={countries} textChanged={countryChanged}/> <CollectionViewNavigator cv={customers} byPage={true} headerFormat="Page {current:n0}"/> <FlexGrid selectionMode="MultiRange" showMarquee={true} isReadOnly={true} itemsSource={customers}> <FlexGridColumn binding="CustomerID" header="Customer ID"/> <FlexGridColumn binding="CompanyName" header="Company Name" width={200}/> <FlexGridColumn binding="ContactName" header="Contact Name" width={150}/> <FlexGridColumn binding="City"/> <FlexGridColumn binding="Country"/> </FlexGrid> </div>); } const container = document.getElementById('app'); if (container) { const root = ReactDOM.createRoot(container); root.render(<App />); }
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>MESCIUS Wijmo Wijmo Firestore Data Limits</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <!-- SystemJS --> <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.40/system.src.js" integrity="sha512-G6mEj6h18+m3MvzdviSDfPle/TfH0//cXcB33AKlNR/Rha0yQsKefDZKRTkIZos97HEGq2JMV1RT5ybMoQ3WsQ==" crossorigin="anonymous"></script> <script src="systemjs.config.js"></script> <script> System.import('./src/app'); </script> </head> <body> <div id="app"></div> </body> </html>
.wj-flexgrid { margin: 1em 0; } .wj-combobox { margin-right: 1em; }
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