Скачать или смотреть Solving the available_quantity Issue with PostgreSQL Generated Columns in Spring Boot

Learn how to resolve the issue of unchanging values in PostgreSQL generated columns when using Spring Boot ORM. Obtain insights into setting up your entity properly for dynamic updates.
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Troubleshooting PostgreSQL Generated Columns in Spring Boot

When working with PostgreSQL, you might encounter a situation where a generated column does not seem to update as you expect. This issue can certainly be perplexing, particularly when you are using an Object-Relational Mapping (ORM) tool like Hibernate in a Spring Boot application. One common scenario involves defining a generated column, like available_quantity, which is meant to represent the difference between two other columns: quantity_total and quantity_ordered.

In this guide, we'll delve into the specific problem of the available_quantity column not reflecting changes made to quantity_ordered and how you can effectively resolve it.

The Problem: Unchanging Values in a Generated Column

You may have set up your available_quantity column using the SQL command below:

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

Despite this setup, you notice that when changes are made to quantity_ordered, the available_quantity column does not update dynamically. Instead, you encounter the following error message:

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

This error suggests that available_quantity is read-only, which is expected for generated columns. So, why isn't it responding to updates in quantity_ordered?

The Solution: Proper Entity Configuration

The good news is that there is a way to resolve this issue. The key lies in configuring your entity correctly in Hibernate. Here's what you need to do:

Step 1: Define the Column in Your Entity

In your Java entity class that corresponds to the products_regions table, you need to specify the available_quantity field with specific annotations. Here’s how you can achieve that:

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

Step 2: Understand the Annotations

@ Column(name = "available_quantity", insertable = false, updatable = false):

insertable = false: This tells Hibernate not to include this field in the SQL INSERT statement.

updatable = false: This indicates that Hibernate should not include this field in the SQL UPDATE statement.

With this configuration, Hibernate recognizes available_quantity as a generated field that should not be directly written to, allowing it to be populated correctly based on changes to quantity_ordered or quantity_total.

Step 3: Validate Your Changes

After making the changes in your entity, you should now be able to modify quantity_ordered and see that the available_quantity updates accordingly when you retrieve the data from the database.

Conclusion

Defining generated columns in PostgreSQL while using Hibernate in Spring Boot can be tricky, especially regarding understanding how to configure your entities correctly. By following the steps outlined above, you can successfully manage generated columns and avoid the frustration of unchanging values.

With the right setup in place, you can leverage the power of PostgreSQL generated columns while seamlessly integrating them into your Spring Boot application. Happy coding!