Скачать или смотреть How to Trigger Insertion of Row into Child Table from Parent Table with RLS Enabled in Supabase

Learn how to resolve the row-level security policy violations in Supabase when inserting data into related tables. This guide offers a step-by-step solution for seamless data operations between parent and child tables.
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How to Trigger Insertion of Row into Child Table from Parent Table with RLS Enabled in Supabase

When working with database systems like Supabase, you may encounter row-level security (RLS) policies that can complicate data insertion processes, especially when dealing with parent-child table relationships. In this guide, we'll explore a common issue faced by developers: the violation of RLS policies when inserting rows into a parent table that subsequently triggers an insertion into a child table. Let's discuss the scenario and offer a solution to overcome this challenge.

Understanding the Problem

Imagine you have a parent table named TEAM and a child table called MEMBERS. The structure of these tables is as follows:

TEAM Table Structure

id: (uuid) - Unique identifier for the team.

owner: (uuid) - Foreign key that links to the user (owner of the team).

MEMBERS Table Structure

team_id: (uuid) - Foreign key that links to the TEAM table.

member_id: (uuid) - Foreign key that links to the user who is a member of the team.

In your application, each owner is also a member of the team. To automate the process of adding a corresponding row in MEMBERS when a new team is created, you have set up a trigger that fires AFTER INSERT on the TEAM table. However, upon attempting to create a new team, you encounter the following error:

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

Reasons for the Error

The RLS policy on the MEMBERS table restricts insert operations to only those who are team owners.

The RLS policy is defined using a function that checks if the current user is the owner of the team, and this check fails during the trigger execution.

Analyzing the Solution

To resolve this issue, we need to adjust the RLS policy on the MEMBERS table to ensure that the insertion from the trigger does not violate it. Here's how we can do that effectively:

Step 1: Modify the RLS Policy

Instead of checking if the user is the team owner based on the insertion action's context, we should check if the new member belongs to the owner of the team. Update your RLS policy as follows:

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

This policy checks explicitly if the team.id matches the member.team_id and that the team.owner matches the authenticated user's ID (auth.uid()).

Step 2: Implement the Trigger Correctly

Ensure that your trigger correctly captures the insertion into the MEMBERS table only after the new team has been added successfully. Since the RLS check is now defined more efficiently, it should not raise issues during the insert operation.

Step 3: Testing the Updates

After implementing the new RLS policy, test the functionality by creating new teams via your application (e.g., using cURL). If everything is configured correctly, you should no longer encounter the RLS violation error, and the respective entry in the MEMBERS table should be created without issues.

Conclusion

Working with row-level security in Supabase can be challenging, especially when handling parent-child relationships in your database. However, by adjusting the RLS policies and making sure they are contextually aware of the data being inserted, you can streamline your operations and eliminate errors. Follow the steps outlined above to ensure seamless data insertion between tables in your Supabase projects.

Feel free to share your experiences or ask questions about RLS and triggers in the comments below!