Possible Unhandled Promise Rejection

Explanation of the problem

The encountered problem revolves around a database used by the app that undergoes downloading and installation. To investigate the issue, tests were conducted to replicate it. The current workflow involves opening the app, downloading the database, and proceeding with its installation. Subsequently, the user can select items from the WarehouseInventory table present within the database. In order to recreate the problem, the database was renamed in the iOS simulator to render it inaccessible along with its associated table.

The anticipated behavior was that an error would be caught through a promise, facilitating the handling of the issue and allowing the flow to continue. However, the actual behavior differs. Instead of triggering a catch statement to handle the error, a new database is created. Consequently, when attempting to access the WarehouseInventory table, the application fails to locate it, resulting in the following error being displayed in the yellow box:

 

YellowBox.js:67 Possible Unhandled Promise Rejection (id: 0):
Object {
  "code": 5,
  "message": "no such table: WarehouseInventory",
}

 

Getting a sense of what’s actually happening inside a live application is a frustrating experience, one that relies mostly on querying and observing whatever logs were written during development.
Lightrun is a Developer Observability Platform, allowing developers to add telemetry to live applications in real-time, on-demand, and right from the IDE.

• Instantly add logs to, set metrics in, and take snapshots of live applications
• Insights delivered straight to your IDE or CLI
• Works where you do: dev, QA, staging, CI/CD, and production

Start for free today

Problem solution for: Possible Unhandled Promise Rejection

To address the issue of not being able to catch exceptions related to SQLite errors and improve the handling of the encountered problem, the following steps can be taken:

1. Implement Error Handling: Modify the code to properly handle exceptions and errors that occur during SQLite operations. Specifically, ensure that promises are appropriately caught and error messages are handled. This can be achieved by using try-catch blocks or utilizing the .catch() method on promises to capture any potential errors.

 

// Example implementation with try-catch block
try {
  // Code block where SQLite operations are performed
  // ...
} catch (error) {
  // Handle the error appropriately
  console.error('An error occurred:', error);
}

 

2. Enhance Logging and Debugging: To gain more insight into the issue and potential error sources, enhance the logging and debugging capabilities of the application. This includes logging relevant information, such as error messages, query details, and stack traces. Additionally, leverage debugging tools provided by the development environment to step through the code and identify any potential issues or unexpected behavior.

 

// Example of enhanced logging with additional information
console.error('Error occurred while executing query:', error);
console.debug('Query details:', query);
console.debug('Stack trace:', error.stack);

 

3. Consider Database Initialization: Review the database initialization process and ensure that it properly handles scenarios where the database or its associated tables are not available or have been renamed. Add appropriate checks and error handling mechanisms to handle such situations gracefully. This may involve verifying the existence of required tables or implementing fallback mechanisms to handle missing tables.

 

// Example of database initialization with error handling
// ...
const warehouseInventoryTableExists = await checkTableExists('WarehouseInventory');
if (!warehouseInventoryTableExists) {
  console.error('The WarehouseInventory table does not exist.');
  // Handle the situation appropriately, such as showing an error message or performing fallback actions.
}
// ...

 

By implementing these steps, you can enhance error handling, gain better visibility into the issue, and ensure more robust handling of SQLite errors within the React Native application.

 

Problem 1: Database Initialization Failure Description: One common issue encountered with react-native-sqlite-storage is the failure to initialize the SQLite database properly. This problem typically occurs when attempting to open or create a database but encountering an error during the process. As a result, subsequent operations such as table creation, data insertion, or querying cannot be performed.

Solution: To resolve this issue, it is essential to ensure that the database initialization process is handled correctly. This includes providing the correct path to the database file, handling errors during database opening or creation, and verifying the successful initialization of the database.

 

import SQLite from 'react-native-sqlite-storage';

// Database initialization
const db = SQLite.openDatabase(
  {
    name: 'mydatabase.db',
    location: 'default',
  },
  () => {
    // Success callback
    console.log('Database opened successfully.');
  },
  (error) => {
    // Error callback
    console.error('Failed to open database:', error);
  }
);

 

Problem 2: Data Retrieval Issues Description: Another common problem encountered with react-native-sqlite-storage is related to retrieving data from the SQLite database. This issue may manifest as incorrect or missing data returned from queries, unexpected results, or difficulties in handling asynchronous nature of data retrieval.

Solution: To address data retrieval issues, it is important to ensure that the queries are written correctly and that the asynchronous nature of the operations is handled appropriately. Additionally, proper error handling should be implemented to catch any potential errors during the data retrieval process.

 

// Example of data retrieval with query and error handling
db.transaction((tx) => {
  tx.executeSql(
    'SELECT * FROM users',
    [],
    (tx, result) => {
      // Process the result
      const rows = result.rows;
      for (let i = 0; i < rows.length; i++) {
        const user = rows.item(i);
        console.log('User:', user);
      }
    },
    (error) => {
      // Error callback
      console.error('Error retrieving data:', error);
    }
  );
});

 

Problem 3: Performance and Memory Management Description: react-native-sqlite-storage may encounter performance and memory management issues when working with large amounts of data or executing complex queries. This can result in slow query execution, increased memory usage, and potential crashes or freezes.

Solution: To optimize performance and improve memory management, several techniques can be employed. These include:

• Utilizing appropriate indexing on the database tables to improve query performance.
• Limiting the amount of data fetched at once using pagination or limiting the number of rows returned.
• Properly closing and releasing database connections after usage to free up memory resources.
• Optimizing complex queries by refining the logic or breaking them into smaller, more manageable queries.

 

// Example of closing and releasing the database connection
db.close((error) => {
  if (error) {
    console.error('Error closing the database:', error);
  } else {
    console.log('Database closed successfully.');
  }
});

 

By addressing these common problems and implementing the suggested solutions, you can overcome issues related to database initialization, data retrieval, and performance in react-native-sqlite-storage.

 

A brief introduction to react-native-sqlite-storage

React Native SQLite Storage (react-native-sqlite-storage) is a popular library used for integrating SQLite database functionality into React Native applications. It provides a simple and efficient way to perform database operations such as database creation, table creation, data insertion, querying, and more. By leveraging the power of SQLite, a lightweight and widely adopted database engine, react-native-sqlite-storage allows developers to build robust and scalable mobile applications with persistent data storage capabilities.

This library offers a comprehensive set of features and APIs for working with SQLite databases in a React Native environment. It provides methods for opening, closing, and managing database connections, executing SQL queries, handling asynchronous operations, and handling errors. Additionally, react-native-sqlite-storage supports advanced functionalities such as transactions, batch processing, and database encryption, making it suitable for a wide range of application requirements. With its efficient and reliable performance, react-native-sqlite-storage is a preferred choice for developers looking to implement local data storage in their React Native projects.

Most popular use cases for react-native-sqlite-storage

 

Local Data Persistence: react-native-sqlite-storage enables developers to implement local data persistence in React Native applications. It allows for the creation and management of SQLite databases, offering a structured and efficient way to store and retrieve data. With the ability to execute SQL queries, developers can easily perform CRUD (Create, Read, Update, Delete) operations on database tables. Here is an example of creating a table and inserting data using react-native-sqlite-storage:

import SQLite from 'react-native-sqlite-storage';

// Open a database connection
const db = SQLite.openDatabase({ name: 'mydatabase.db', createFromLocation: 1 });

// Create a table
db.transaction((tx) => {
  tx.executeSql(
    'CREATE TABLE IF NOT EXISTS Users (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, age INTEGER)',
    [],
    (_, result) => {
      console.log('Table created successfully');
    },
    (_, error) => {
      console.log('Error creating table:', error);
    }
  );
});

// Insert data into the table
db.transaction((tx) => {
  tx.executeSql(
    'INSERT INTO Users (name, age) VALUES (?, ?)',
    ['John', 30],
    (_, result) => {
      console.log('Data inserted successfully');
    },
    (_, error) => {
      console.log('Error inserting data:', error);
    }
  );
});

 

2. Data Synchronization: react-native-sqlite-storage can be utilized for data synchronization between a remote server and a local database. By retrieving data from a server API and storing it in the SQLite database, the application can provide offline access to data and sync it with the server when the device is back online. This allows for seamless data access and ensures data integrity. The library’s transaction support and efficient query execution make it well-suited for synchronizing data updates between the server and the local database.
3. Performance Optimization: With react-native-sqlite-storage, developers can optimize the performance of their React Native applications by leveraging the speed and efficiency of SQLite. By storing data locally and utilizing SQLite’s indexing and querying capabilities, developers can achieve faster data retrieval and manipulation operations. This is particularly beneficial when working with large datasets or complex data structures. The library also provides features such as prepared statements and parameterized queries, allowing for optimized and secure database operations.