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Expo Go is a sandbox environment that allows you to quickly test your application without building a development build. To enable PowerSync in Expo Go, we provide a JavaScript-based database adapter: @powersync/adapter-sql-js.

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@powersync/adapter-sql-js

@powersync/adapter-sql-js is a development package for PowerSync which uses SQL.js to provide a pure JavaScript SQLite implementation. This eliminates the need for native dependencies and enables development with Expo Go and other JavaScript-only environments. Under the hood, it uses our custom fork powersync-sql-js - a fork of SQL.js (SQLite compiled to JavaScript via Emscripten) that loads the PowerSync SQLite core extension.
This package is in an alpha release.Expo Go Sandbox Environment Only This adapter is specifically designed for Expo Go and similar JavaScript-only environments. It will be much slower than native database adapters and has limitations. Every write operation triggers a complete rewrite of the entire database file to persistent storage, not just the changed data. In addition to the performance overheads, this adapter doesn’t provide any of the SQLite consistency guarantees - you may end up with missing data or a corrupted database file if the app is killed while writing to the database file.

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Usage

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Quickstart

  1. Create a new Expo app:
npx create-expo-app@latest my-app
  1. Navigate to your app directory and start the development server:
cd my-app && npm run ios
  1. In a new terminal tab, install PowerSync dependencies:
npm install @powersync/react-native @powersync/adapter-sql-js
  1. Replace the code in app/(tabs)/index.tsx with:
app/(tabs)/index.tsx
import { SQLJSOpenFactory } from "@powersync/adapter-sql-js";
import { PowerSyncDatabase, Schema } from "@powersync/react-native";
import { useEffect, useState } from "react";
import { Text } from "react-native";

export const powerSync = new PowerSyncDatabase({
  schema: new Schema({}), // todo: define the schema - see Next Steps below
  factory: new SQLJSOpenFactory({
    dbFilename: "example.db",
  }),
});

export default function HomeScreen() {
  const [version, setVersion] = useState<string | null>(null);

  useEffect(() => {
    powerSync.get("select powersync_rs_version();").then((r) => {setVersion(JSON.stringify(r))});
  }, []);

  return (
      <>{version && <Text style={{fontSize: 24, fontWeight: 'bold'}}>PowerSync Initialized - {version}</Text>}</>
  );
}

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Next Steps

After adding PowerSync to your app:
  1. Define what data to sync by setting up Sync Rules
  2. Implement your SQLite client schema
  3. Connect to PowerSync and your backend

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Data Persistence

The default version of this adapter uses in-memory persistence, but you can specify your own persister option to the open factory. See an example in the package README.

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Moving Beyond Expo Go

When you’re ready to move beyond the Expo Go sandbox environment - whether for native development builds or production deployment - we recommend switching to our recommended native database adapter, based on OP-SQLite.
OP-SQLite cannot run in Expo Go because it require native code compilation. Specifically, PowerSync needs a SQLite implementation that can load the PowerSync SQLite core extension, which isn’t possible in Expo Go’s prebuilt app container.
This adapter provides better performance, full SQLite consistency guarantees, and are suitable for both development builds and production deployment. See the SDKs Installation details for setup instructions.

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Switching Between Adapters - Example

If you want to keep using Expo Go alongside development and production builds, you can switch between different adapters based on the Expo executionEnvironment:
SystemProvider.tsx
import { SQLJSOpenFactory } from "@powersync/adapter-sql-js";
import { DatabaseSource, PowerSyncDatabase } from "@powersync/react-native";
import Constants from "expo-constants";

const isExpoGo = Constants.executionEnvironment === "storeClient";

const source: DatabaseSource = isExpoGo ?
  { factory: new SQLJSOpenFactory({ dbFilename: "app.db" }) }
  : { database: { dbFilename: "sqlite.db" } };

export const powerSync = new PowerSyncDatabase({
  schema: AppSchema,
  ...source,
});