How do I create complex SQL rules for RLS in Supabase

Enable RLS on Tables

1. Create Tables: Create tables in your Supabase database. For example, create a `teams` table and a `members` table.

sql
   CREATE TABLE teams (
       id SERIAL PRIMARY KEY,
       name TEXT
   );

   CREATE TABLE members (
       team_id BIGINT REFERENCES teams,
       user_id UUID REFERENCES auth.users
   );
   

2. Enable RLS: Enable RLS on the tables you want to secure.

sql
   ALTER TABLE teams ENABLE ROW LEVEL SECURITY;

   ALTER TABLE members ENABLE ROW LEVEL SECURITY;
   

Create Policies

1. Basic Policy: Create a basic policy to restrict access to a table based on a column. For example, restrict access to the `teams` table based on the `id` column.

sql
   CREATE POLICY "Team members can view their own team details if they belong to the team."
       ON teams
       FOR SELECT
       TO authenticated
       USING (auth.uid() IN (
           SELECT user_id
           FROM members
           WHERE team_id = id
       ));
   

2. Advanced Policy with Joins: Create a policy that includes table joins. For example, restrict access to the `tasks` table based on the `organization_id` column and the `user_id` column.

sql
   CREATE POLICY "Only allow organizations to create tasks if they have enough quota"
       ON tasks
       AS RESTRICTIVE
       FOR INSERT
       TO authenticated
       WITH CHECK (
           organization_can_create_task(organization_id)
       );
   

Use Security Definer Functions

1. Security Definer Function: Create a security definer function to bypass RLS policies. For example, create a function that can be called by the `service_role` to bypass RLS.

sql
   CREATE OR REPLACE FUNCTION create_task(user_id BIGINT, name TEXT)
       RETURNS tasks AS $$
   BEGIN
       IF current_setting('role') != 'service_role' THEN
           RAISE EXCEPTION 'Only admins can call this function';
       END IF;
       INSERT INTO tasks (user_id, name) VALUES (user_id, name);
       RETURN (SELECT * FROM tasks WHERE id = currval('tasks_id_seq'));
   END;
   $$ LANGUAGE plpgsql SECURITY DEFINER;
   

Restrictive Policies

1. Restrictive Policy: Create a restrictive policy to restrict write access to a table based on a column. For example, restrict write access to the `users` table based on the `id` column.

sql
   CREATE POLICY "Restrict write access to authenticated users"
       ON users
       AS RESTRICTIVE
       FOR INSERT
       TO authenticated
       WITH CHECK (id = auth.uid());
   

Common RLS Policies

1. Restricting Access to a Table Based on a Column: Restrict access to a table based on a column.

sql
   CREATE POLICY "Restrict access to user tasks to their own tasks"
       ON tasks
       FOR SELECT
       TO authenticated
       USING (user_id = auth.uid());
   

2. Restricting Write Access to a Table Based on a Column: Restrict write access to a table based on a column.

sql
   CREATE POLICY "Restrict write access to authenticated users"
       ON users
       AS RESTRICTIVE
       FOR INSERT
       TO authenticated
       WITH CHECK (id = auth.uid());
   

Use db_pre_request

1. db_pre_request: Use `db_pre_request` to simplify complex RLS policies. For example, use it to set a claim that can be used for the rest of the records.

sql
   db_pre_request: function() {
       const user = auth.user();
       const orgId = user.org_id;
       setClaim('orgId', orgId);
   }
   

Example Policy with db_pre_request

1. Policy with db_pre_request: Create a policy that uses `db_pre_request` to set a claim.

sql
   CREATE POLICY "Only allow organizations to create tasks if they have enough quota"
       ON tasks
       AS RESTRICTIVE
       FOR INSERT
       TO authenticated
       WITH CHECK (
           organization_can_create_task(getClaim('orgId'))
       );
   

By following these steps and examples, you can create complex SQL rules for Row Level Security in Supabase to secure your data effectively.