Creating User Profiles on Sign-Up in Supabase

Supabase stores authentication-related information (unique ID, email, password, etc.) in the auth.users table when users sign up. The auth schema isn't publicly accessible for security reasons, so you can't store additional information on your users in this table.

Depending on what type of application you are building, you might need a profile table containing profile information your users can interact with. In this post, we will:

• Create a simple profile table in the public schema.
• Enable Row-Level Security on it and restrict access for users to their own profile data.
• Write a database trigger that automatically creates a row for every user on sign-up.

Creating & Securing a Profile Table

We start by creating a profile table with two columns: id referencing a user ID in the auth.users table, and display_name.

CREATE TABLE public.profile (
  id UUID REFERENCES auth.users NOT NULL,
  display_name TEXT NULL,
  PRIMARY KEY (id)
);

Supabase uses PostgREST to access the Postgres database via its API (i.e., the supabase API you use in your client application). By default, a table in the public schema can be accessed without restriction.

However, in our case, we want to restrict access on this table so that users can only select and update data that belongs to them. We are going to use Row-Level Security for this.

ALTER TABLE public.profile
  ENABLE ROW LEVEL SECURITY;

When Row-Level Security is enabled for a table, all access to this table must be allowed by a row security policy. The idea here is: "Everything is forbidden unless explicitly allowed."

The first row security policy we introduce allows a user to SELECT their own profile data:

CREATE POLICY
  "Can only view own profile data."
  ON public.profile
  FOR SELECT
  USING ( auth.uid() = id );

The second row security policy allows a user to UPDATE their own profile data:

CREATE POLICY
  "Can only update own profile data."
  ON public.profile
  FOR UPDATE
  USING ( auth.uid() = id );

The idea behind these policies is to specifically grant rights to SELECT or UPDATE rows where the id is set to the authenticated user's unique ID. Since id is the primary key of the profile table, this effectively leaves only one row: the user's own profile data.

If you want to know how to handle public and private access, I recommend reading the page Managing User Data from the Supabase documentation.

Automatically Creating Profiles on Sign-Up

When a user signs up or signs in with a Third-Party provider (e.g. Twitter, GitHub, Google, etc.), a new row is inserted into the auth.users table. Ideally, we want to create a new profile at the same time. An easy way to do so is to use triggers.

The following statement creates a trigger called create_profile_on_signup that calls the function create_profile_for_new_user() whenever a new row is inserted into the auth.users table:

CREATE TRIGGER
  create_profile_on_signup
  AFTER INSERT ON auth.users
  FOR EACH ROW
  EXECUTE PROCEDURE
    public.create_profile_for_new_user();

The function create_profile_for_new_user() simply inserts a new row into our profile table:

CREATE FUNCTION
  public.create_profile_for_new_user()
  RETURNS TRIGGER AS
  $$
  BEGIN
    INSERT INTO public.profile (id)
    VALUES (NEW.id);
    RETURN NEW;
  END;
  $$ LANGUAGE plpgsql SECURITY DEFINER;

The NEW keyword refers to a variable holding the new database row (i.e., the one that was just inserted into the auth.users table).

There's one thing missing, though: The display_name isn't set. Technically, this isn't a problem, as the column is nullable. For Third-Party logins, however, we can access certain metadata that allows us to prefill this column with a sensible value.

The auth.users table has a JSONB column called raw_user_meta_data containing information on the user depending on the Third-Party provider used for signing in. For example, it usually contains a user_name field.

Making use of this, we can prefill the display_name with this username like this:

CREATE FUNCTION
  public.create_profile_for_new_user()
  RETURNS TRIGGER AS
  $$
  BEGIN
    INSERT INTO public.profile (id, display_name)
    VALUES (
      NEW.id,
      NEW.raw_user_meta_data ->> 'user_name'
    );
    RETURN NEW;
  END;
  $$ LANGUAGE plpgsql SECURITY DEFINER;

Now, whenever a user signs up, a new profile is created with its display_name set to the username used with the Third-Party provider or to NULL when you use Supabase's sign in (here you can fill it from within the client application).

Recap

• The auth.users table stores authentication-related information.
• You can't access or modify this table from within your application for (obvious) security reasons.
• We created a profile table with two columns id and display_name.
• We enabled Row-Level Security for this table and restricted access for users to their own data.
• We created a trigger and function to automatically insert a new row into profile when a new row is inserted into auth.users table.
• When a user signs up or signs in with a Third-Party provider, a new row is inserted into auth.users.

References

• I can highly recommend the Next.js Subscription Payments Starter, which uses this idea here.