Optimizing Geo-Data Pagination for High Performance in .NET 5 WebAPI

Discover effective strategies for executing high-performance pagination of geo-data in your .NET 5 WebAPI, ensuring efficient sorting and retrieval of geolocation data.
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Optimizing Geo-Data Pagination for High Performance in .NET 5 WebAPI

In today's mobile applications, efficiently handling large datasets is crucial for providing a smooth user experience. This is particularly true when working with geo-data, where users expect quick and accurate results based on their proximity to various locations. If you're building a .NET 5 WebAPI to serve a mobile app, you might be faced with the challenge of paginating a few million entries from an Azure SQL Server database, all of which feature geolocation information. The goal is to quickly return entries sorted by the user's current location in manageable chunks. In this guide, we'll explore how to optimize your LINQ queries for better performance.

The Problem

Consider the original approach for pagination where the query looks something like this:

[[See Video to Reveal this Text or Code Snippet]]

While this method retrieves the desired entries (30 at a time), it requires the full dataset to be processed and sorted before pagination is applied. This results in performance issues, especially with larger datasets. The key problem lies in the way the query handles sorting by distance, which can lead to inefficient execution and excessive resource consumption.

Solution Breakdown

To improve the situation, we need to ensure that sorting and pagination occurs on the database side, rather than in memory. Follow these steps to optimize your LINQ queries effectively.

Step 1: Identify Core Problems with Current Query

The suspect part of the code is the p.Location.Distance(currentLocation), which may trigger client-side evaluation rather than server-side execution. This leads to all data being retrieved and sorted in memory, which is not scalable.

Step 2: Use Coordinate Values for Efficient Sorting

Instead of calculating distance directly, we can rearrange the query to utilize the X and Y coordinates for a more efficient comparison:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

Coordinate Calculation: Here, x and y represent the coordinates of the current location.

Ordering: The entries are ordered based on the absolute difference in both the x and y coordinates from the user's location. This allows the database to perform the sorting efficiently without calculating the exact distance.

Pagination: Skip and Take are utilized to fetch the specific set of records required for the current page.

Step 3: Calculating Actual Distance (if Needed)

If you require the actual distance between points for display purposes, you can compute it using the Pythagorean theorem and ensure that Entity Framework translates it into SQL:

[[See Video to Reveal this Text or Code Snippet]]

This way, you might obtain the distance while keeping the order of points for pagination.

Conclusion

By ensuring that your sorting mechanism is performed server-side, you can significantly enhance the performance of your pagination logic in .NET 5 WebAPI applications. Utilizing coordinate comparison rather than a direct distance calculation helps keep the database interactions efficient and reduces client-side overhead.

Implementing these strategies will help you manage large datasets more effectively, resulting in a better overall experience for your mobile app users. Happy coding!