The Problem with Primary Keys

Oct 13, 2025 by pinkandtrash.com 91 views

Introduction

When working with Supabase and TypeScript, generated types can be a powerful tool for ensuring type safety and reducing errors in our code. However, when dealing with relationships between tables, we may encounter issues with the generated types. In this article, we will explore a common problem where generated types do not work as expected for relationships.

Understanding the Issue

The issue described in the bug report is that when trying to retrieve related data using a query like supabase.from('group').select('displayName, event (id)'), the generated TypeScript types do not work as expected. Instead of returning the expected type, the code outputs an error message indicating that it could not find the relation between the group and event tables.

Generated DB Types

To better understand the issue, let's take a look at the generated DB types for both the event and group tables. These types are crucial in determining the structure of the data and how it should be accessed.

// Generated DB types for the event table
interface Event {
  id: string;
  name: string;
  promoter: string;
  // Other properties...
}

// Generated DB types for the group table
interface Group {
  id: string;
  displayName: string;
  events: Event[];
  // Other properties...
}

As we can see, the Group interface has an events property that is an array of Event objects. This indicates a one-to-many relationship between the group and event tables, where one group can have many events assigned to it.

The Problem with Primary Keys

In the bug report, it is mentioned that the promoter column in the event table is not a primary key, but rather a foreign key referencing the id column in the group table. This is a common scenario in database design, where a many-to-one relationship is established between two tables.

However, when it comes to generated types, this can cause issues. The reason is that TypeScript requires a clear definition of the relationship between tables, which is not always possible when dealing with foreign keys.

Workarounds and Solutions

So, what can we do to resolve this issue? Here are a few workarounds and solutions that may help:

1. Use a Many-to-Many Relationship

One possible solution is to establish a many-to-many relationship between the group and event tables. This can be achieved by creating a new table that acts as a bridge between the two tables.

// New table to establish a many-to-many relationship
interface GroupEvent {
  group_id: string;
  event_id: string;
}

By doing this, we can create a clear definition of the relationship between the group and event tables, which should resolve the issue with the generated types.

2. Use a Custom Type Definition

Another solution is to create a custom type definition for the Group interface that includes the events property. This can be done by creating a new type that extends the Group interface.

// Custom type definition for the Group interface
interface GroupWithEvents extends Group {
  events: Event[];
}

By doing this, we can create a custom type definition that includes the events property, which should resolve the issue with the generated types.

3. Use a Type Mapping

A third solution is to use a type mapping to define the relationship between the group and event tables. This can be done by creating a new type that maps the group table to the event table.

// Type mapping to define the relationship between the group and event tables
interface GroupEventMapping {
  group: Group;
  events: Event[];
}

By doing this, we can create a type mapping that defines the relationship between the group and event tables, which should resolve the issue with the generated types.

Conclusion

In conclusion, the issue with generated types not working for relationships in Supabase and TypeScript can be resolved by using one of the workarounds and solutions described above. By creating a custom type definition, using a type mapping, or establishing a many-to-many relationship, we can create a clear definition of the relationship between tables, which should resolve the issue with the generated types.

Additional Resources

For more information on how to work with generated types in Supabase and TypeScript, please refer to the following resources:

Introduction

In our previous article, we explored a common problem where generated types do not work as expected for relationships in Supabase and TypeScript. We also discussed several workarounds and solutions to resolve this issue. In this article, we will provide a Q&A section to address some of the most frequently asked questions related to this topic.

Q: What is the cause of the issue with generated types not working for relationships?

A: The cause of the issue is due to the way TypeScript handles relationships between tables. When dealing with foreign keys, TypeScript requires a clear definition of the relationship between tables, which is not always possible.

Q: How can I resolve the issue with generated types not working for relationships?

A: There are several workarounds and solutions to resolve this issue. Some of the most common solutions include:

Creating a many-to-many relationship between tables
Using a custom type definition to include the related table
Using a type mapping to define the relationship between tables

Q: What is a many-to-many relationship, and how can I establish it?

A: A many-to-many relationship is a type of relationship between two tables where one table can have multiple records related to multiple records in the other table. To establish a many-to-many relationship, you can create a new table that acts as a bridge between the two tables.

Q: How can I create a custom type definition to include the related table?

A: To create a custom type definition, you can extend the original type with the related table. For example, if you have a Group type and you want to include the Event type, you can create a new type that extends the Group type.

interface GroupWithEvents extends Group {
  events: Event[];
}

Q: What is a type mapping, and how can I use it to define the relationship between tables?

A: A type mapping is a way to define the relationship between two tables by creating a new type that maps the first table to the second table. For example, if you have a Group type and you want to map it to the Event type, you can create a new type that includes both types.

interface GroupEventMapping {
  group: Group;
  events: Event[];
}

Q: How can I ensure that my generated types work as expected for relationships?

A: To ensure that your generated types work as expected for relationships, you can follow these best practices:

Use a clear and consistent naming convention for your types and properties
Use interfaces and type definitions to define the structure of your data
Use type mappings and custom type definitions to define relationships between tables
Test your code thoroughly to ensure that it works as expected

Q: What are some common pitfalls to avoid when working with generated types and relationships?

A: Some common pitfalls to avoid when working with generated types and relationships include:

Not defining the relationship between tables clearly
Not using a consistent naming convention for types and properties
Not testing your code thoroughly
Not using type mappings and custom type definitions to define relationships between tables

Conclusion

Additional Resources

For more information on how to work with generated types in Supabase and TypeScript, please refer to the following resources:

By following these resources and using the workarounds and solutions described above, we can ensure that our generated types work as expected for relationships in Supabase and TypeScript.