Скачать или смотреть How to Automatically Update a Relation Column in TypeORM with NestJS and Postgres

Discover how to automatically update a relation column based on other relations in TypeORM with NestJS and PostgreSQL while retaining code efficiency.
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How to Automatically Update a Relation Column in TypeORM with NestJS and PostgreSQL

If you're building a complex application where users can rate photos, leave comments, and interact with multiple related entities, you might run into some challenges with maintaining those relationships. This post dives into the specifics of handling updates within a relational database using TypeORM in a NestJS environment. We’ll focus on a scenario where you want to automatically update a photo rating in comments after a user changes their rating.

The Problem

You have three main entities: Photo, PhotoComment, and PhotoRating. Users can rate photos and comment on them, but each photo can have multiple comments and multiple ratings from different users (only one rating per user). The problem arises when you want to ensure that users see their latest rating in each comment they make. When attempting to update a rating, you discovered that the changes did not reflect in the PhotoComment entity.

Despite the ratePhoto method working correctly, it was found that the necessary connections between PhotoRating and PhotoComment were not maintained during the update process.

Let's take a closer look at how to implement a solution to this problem.

Step-by-Step Solution

1. Use a Transaction for Data Integrity

One of the most important aspects of database operations is ensuring that changes are consistent. Using a transaction allows multiple operations to be executed together, ensuring that all or none of them succeed.

Here’s the modified code to include a transaction:

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2. Understand the Entity Relationships

Ensure that your entities are properly set up. Here’s a simplified view of the entities:

Photo Entity

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PhotoComment Entity

Your PhotoComment entity should simply refer to the Photo and PhotoRating entities without unnecessary configurations.

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PhotoRating Entity

Ensure the PhotoRating is set as unique for each user and photo combination.

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3. Performance Considerations

Using the update() method instead of fetching and saving entities manually helps improve the performance of updates across multiple comments. It’s critical for scalability, especially when users can comment frequently on photos.

Conclusion

By leveraging transactions and the update() method in TypeORM, you can efficiently maintain the relationships in your database without unnecessary overhead. This streamlined approach allows your users to see their latest ratings associated with their comments while keeping your codebase clean and efficient.

Now that you understand how to handle relational updates between entities, you can enhance the user experience in your application significantly!