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Why does PostgREST give me a 404 error when I try to update a record that has a RLS policy that prevents updating? When I satisfy the RLS policy it returns 200

I think what's happening here is that after you update or insert a record, Postgrest is doing a select on the record to return data back to you.  I've had this problem before when I wanted a user to `INSERT` data but not be able to `SELECT` data (for logging purposes only.)

The solution was to add this as a parameter to my `INSERT` call with the `Supabase JS Client`:  {returning: 'minimal'}

```
    const { data, error } = await supabase
    .from('device_log')
    .insert([
      { 
        userid: 'aaa',
        model: 'bbb',
       }
    ],{returning: 'minimal'});
```

I may be way off base here for your use case, but in general, I've had problems before when I didn't understand that doing an `insert` or `update` also triggered a `select` behind the scenes.  Hope this helps.