In the vast world of databases, fetching data efficiently is crucial for applications, especially when dealing with large datasets. One powerful approach to accomplish this is through cursor-based pagination using TypeORM. In this guide, we’ll explore the steps to implement this method, troubleshoot common issues, and maximize your development experience.

What is Cursor-Based Pagination?

Cursor-based pagination is a technique used to retrieve a subset of records from a larger dataset. Unlike traditional offset-based pagination, which can become inefficient with large pages, cursor-based pagination uses a unique identifier (cursor) to keep track of your position in the data set. This results in faster queries and a smoother user experience.

Installation

To get started, you’ll need to install the TypeORM Cursor Pagination package. Run the following command:

npm install typeorm-cursor-pagination --save

Usage

Now that you have installed the necessary package, let’s set up pagination. We’ll break it down step by step.

Step 1: Query the First Page Without Any Cursor

Here’s how to retrieve the first page of your dataset:

import { getConnection } from 'typeorm';
import buildPaginator from 'typeorm-cursor-pagination';

const queryBuilder = getConnection()
    .getRepository(User)
    .createQueryBuilder('user')
    .where('user.gender = :gender', { gender: 'male' });

const paginator = buildPaginator({
    entity: User,
    paginationKeys: ['id'],
    query: {
        limit: 10,
        order: 'ASC',
    },
});

const { data, cursor } = await paginator.paginate(queryBuilder);

This code is like a librarian retrieving a set number of books from a library. The queryBuilder functions as a librarian who filters the available books based on specific criteria (in this case, gender), while the paginator chooses how many books (records) to display and in what order. Thus, cursor-based pagination helps retrieve data effectively.

Step 2: Querying the Next Page

To fetch the next page using the ‘afterCursor’, you can use the following code:

const nextPaginator = buildPaginator({
    entity: User,
    paginationKeys: ['id'],
    query: {
        limit: 10,
        order: 'ASC',
        afterCursor: cursor.afterCursor,
    },
});

const { data, cursor } = await nextPaginator.paginate(queryBuilder);

Step 3: Querying the Previous Page

Fetching the previous page can be managed easily with the ‘beforeCursor’:

const prevPaginator = buildPaginator({
    entity: User,
    paginationKeys: ['id'],
    query: {
        limit: 10,
        order: 'ASC',
        beforeCursor: cursor.beforeCursor,
    },
});

const { data, cursor } = await prevPaginator.paginate(queryBuilder);

Integration Testing with Docker

If you wish to run integration tests to test your implementation, you can start the testing process using the following command:

npm run test:docker

Troubleshooting Tips

If you encounter issues during your implementation, consider the following troubleshooting suggestions:

• Ensure you have the correct TypeORM version and that it is properly configured in your project.
• Check your database connection and query structure for any inconsistencies.
• Look at the pagination keys you are using and ensure they match the entity properties.
• If the paginator does not return results, verify that the limit value is set appropriately and not too low or too high.
• Review the logs for any error messages that can give you a clue about what went wrong.

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Conclusion

Cursor-based pagination is an efficient way to handle large datasets in TypeORM, ensuring that your application remains responsive and user-friendly. By following the steps outlined above, you can quickly set up and implement cursor-based pagination within your application.

At fxis.ai, we believe that such advancements are crucial for the future of AI, as they enable more comprehensive and effective solutions. Our team is continually exploring new methodologies to push the envelope in artificial intelligence, ensuring that our clients benefit from the latest technological innovations.