First things first, head over to the Supabase dashboard by logging in at app.supabase.io. If you've got multiple projects, just pick the one you need.

Once you're in your project dashboard, look for the "Database" section. You'll find it on the left-hand sidebar. Click on it.

Inside the "Database" section, you'll see an option for the "SQL Editor." Go ahead and open that up. This is where the magic happens.

Now, in the SQL Editor, you'll need to write a query to create an index on the table and columns you want. The basic structure looks like this:

CREATE INDEX index_name ON table_name (column_name);

For instance, if you want to create an index on the users table for the email column, your query would be:

CREATE INDEX idx_users_email ON users (email);

Once your query is ready, hit the "RUN" button in the SQL Editor. If everything goes well, your index will be created on the specified table and column.

To make sure your index was created, go to the "Schema" section under "Database." You should see your new index listed under the indexes for the respective table.

Optional: If your table has a lot of data, you might want to check the performance improvement. Run some queries before and after creating the index to see the difference.

And there you have it! By following these steps, you can create a database index in Supabase to boost your query performance.