supabase-expert

name	supabase-expert
description	Expert guide for Supabase integration - database schemas, RLS policies, auth, Edge Functions, and real-time subscriptions. Use when working with Supabase backend features.

Supabase Integration Expert Skill

Overview

This skill helps you build secure, scalable Supabase integrations. Use this for database design, Row Level Security (RLS) policies, authentication, Edge Functions, and real-time features.

Core Principles

1. Security First

• Always enable RLS on tables with user data
• Use service role key only in secure server contexts
• Use anon key for client-side operations
• Test policies thoroughly

2. Type Safety

• Generate TypeScript types from schema
• Use generated types in application
• Keep types in sync with schema changes

3. Performance

• Use indexes for frequently queried columns
• Implement pagination for large datasets
• Use select() to limit returned fields
• Cache when appropriate

Database Schema Design

Basic Table Creation

-- Create a table with standard fields
create table public.items (
  id uuid default gen_random_uuid() primary key,
  created_at timestamp with time zone default timezone('utc'::text, now()) not null,
  updated_at timestamp with time zone default timezone('utc'::text, now()) not null,
  user_id uuid references auth.users(id) on delete cascade not null,
  title text not null,
  description text,
  status text default 'draft' check (status in ('draft', 'published', 'archived'))
);

-- Create updated_at trigger
create or replace function public.handle_updated_at()
returns trigger as $$
begin
  new.updated_at = now();
  return new;
end;
$$ language plpgsql;

create trigger set_updated_at
  before update on public.items
  for each row
  execute function public.handle_updated_at();

-- Create index
create index items_user_id_idx on public.items(user_id);
create index items_status_idx on public.items(status);

Foreign Keys & Relations

-- One-to-many relationship
create table public.comments (
  id uuid default gen_random_uuid() primary key,
  created_at timestamp with time zone default now() not null,
  item_id uuid references public.items(id) on delete cascade not null,
  user_id uuid references auth.users(id) on delete cascade not null,
  content text not null
);

-- Many-to-many relationship
create table public.item_tags (
  item_id uuid references public.items(id) on delete cascade,
  tag_id uuid references public.tags(id) on delete cascade,
  primary key (item_id, tag_id)
);

Row Level Security (RLS)

Basic RLS Patterns

-- Enable RLS
alter table public.items enable row level security;

-- Users can read their own items
create policy "Users can read own items"
  on public.items for select
  using (auth.uid() = user_id);

-- Users can insert their own items
create policy "Users can insert own items"
  on public.items for insert
  with check (auth.uid() = user_id);

-- Users can update their own items
create policy "Users can update own items"
  on public.items for update
  using (auth.uid() = user_id)
  with check (auth.uid() = user_id);

-- Users can delete their own items
create policy "Users can delete own items"
  on public.items for delete
  using (auth.uid() = user_id);

Advanced RLS Patterns

-- Public read, authenticated write
create policy "Anyone can read published items"
  on public.items for select
  using (status = 'published');

create policy "Authenticated users can insert"
  on public.items for insert
  to authenticated
  with check (true);

-- Role-based access
create policy "Admins can do everything"
  on public.items for all
  using (
    exists (
      select 1 from public.user_roles
      where user_id = auth.uid()
      and role = 'admin'
    )
  );

-- Shared access
create policy "Users can read shared items"
  on public.items for select
  using (
    auth.uid() = user_id
    or exists (
      select 1 from public.item_shares
      where item_id = items.id
      and shared_with = auth.uid()
    )
  );

Anonymous/Guest Access

-- Allow anonymous reads
create policy "Anonymous can read public content"
  on public.items for select
  to anon
  using (status = 'published');

-- Allow anonymous inserts (for guest mode)
create policy "Anonymous can create items"
  on public.items for insert
  to anon
  with check (true);

Client Integration

Setup Client (Next.js)

// lib/supabase/client.ts
import { createBrowserClient } from '@supabase/ssr'

export function createClient() {
  return createBrowserClient(
    process.env.NEXT_PUBLIC_SUPABASE_URL!,
    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!
  )
}

// lib/supabase/server.ts
import { createServerClient } from '@supabase/ssr'
import { cookies } from 'next/headers'

export function createServerClient() {
  const cookieStore = cookies()

  return createServerClient(
    process.env.NEXT_PUBLIC_SUPABASE_URL!,
    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
    {
      cookies: {
        get(name: string) {
          return cookieStore.get(name)?.value
        },
      },
    }
  )
}

CRUD Operations

// Query data
const { data, error } = await supabase
  .from('items')
  .select('*')
  .eq('status', 'published')
  .order('created_at', { ascending: false })
  .limit(10)

// Insert data
const { data, error } = await supabase
  .from('items')
  .insert({ title: 'New Item', user_id: userId })
  .select()
  .single()

// Update data
const { data, error } = await supabase
  .from('items')
  .update({ title: 'Updated Title' })
  .eq('id', itemId)
  .select()
  .single()

// Delete data
const { error } = await supabase
  .from('items')
  .delete()
  .eq('id', itemId)

// Complex joins
const { data, error } = await supabase
  .from('items')
  .select(`
    *,
    comments (
      id,
      content,
      user:user_id (
        email
      )
    )
  `)
  .eq('user_id', userId)

Real-time Subscriptions

// Subscribe to changes
const channel = supabase
  .channel('items-changes')
  .on(
    'postgres_changes',
    {
      event: '*',
      schema: 'public',
      table: 'items',
      filter: `user_id=eq.${userId}`,
    },
    (payload) => {
      console.log('Change received!', payload)
      // Update local state
    }
  )
  .subscribe()

// Cleanup
channel.unsubscribe()

Authentication

Email/Password Auth

// Sign up
const { data, error } = await supabase.auth.signUp({
  email: '[e-mail]',
  password: 'password123',
  options: {
    data: {
      display_name: 'User Name',
    },
  },
})

// Sign in
const { data, error } = await supabase.auth.signInWithPassword({
  email: '[e-mail]',
  password: 'password123',
})

// Sign out
const { error } = await supabase.auth.signOut()

// Get current user
const { data: { user } } = await supabase.auth.getUser()

OAuth Providers

// Google OAuth
const { data, error } = await supabase.auth.signInWithOAuth({
  provider: 'google',
  options: {
    redirectTo: `${window.location.origin}/auth/callback`,
  },
})

// Handle callback
// app/auth/callback/route.ts
export async function GET(request: Request) {
  const { searchParams } = new URL(request.url)
  const code = searchParams.get('code')

  if (code) {
    const supabase = createServerClient()
    await supabase.auth.exchangeCodeForSession(code)
  }

  return NextResponse.redirect(new URL('/dashboard', request.url))
}

Auth Middleware

// middleware.ts
import { createServerClient } from '@supabase/ssr'
import { NextResponse } from 'next/server'
import type { NextRequest } from 'next/server'

export async function middleware(request: NextRequest) {
  const response = NextResponse.next()

  const supabase = createServerClient(
    process.env.NEXT_PUBLIC_SUPABASE_URL!,
    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
    {
      cookies: {
        get(name: string) {
          return request.cookies.get(name)?.value
        },
        set(name: string, value: string, options: any) {
          response.cookies.set(name, value, options)
        },
        remove(name: string, options: any) {
          response.cookies.set(name, '', { ...options, maxAge: 0 })
        },
      },
    }
  )

  const { data: { user } } = await supabase.auth.getUser()

  // Redirect to login if not authenticated
  if (!user && request.nextUrl.pathname.startsWith('/dashboard')) {
    return NextResponse.redirect(new URL('/login', request.url))
  }

  return response
}

export const config = {
  matcher: ['/dashboard/:path*'],
}

Edge Functions

Basic Edge Function

// supabase/functions/hello/index.ts
import { serve } from 'https://deno.land/std@0.168.0/http/server.ts'
import { createClient } from 'https://esm.sh/@supabase/supabase-js@2'

serve(async (req) => {
  try {
    // Get Supabase client
    const supabase = createClient(
      Deno.env.get('SUPABASE_URL') ?? '',
      Deno.env.get('SUPABASE_ANON_KEY') ?? '',
      {
        auth: {
          autoRefreshToken: false,
          persistSession: false,
        },
      }
    )

    // Get user from auth header
    const authHeader = req.headers.get('Authorization')
    const token = authHeader?.replace('Bearer ', '')
    const { data: { user } } = await supabase.auth.getUser(token)

    if (!user) {
      return new Response(
        JSON.stringify({ error: 'Unauthorized' }),
        { status: 401, headers: { 'Content-Type': 'application/json' } }
      )
    }

    // Your logic here
    const { data, error } = await supabase
      .from('items')
      .select('*')
      .eq('user_id', user.id)

    return new Response(
      JSON.stringify({ data }),
      { headers: { 'Content-Type': 'application/json' } }
    )
  } catch (error) {
    return new Response(
      JSON.stringify({ error: error.message }),
      { status: 500, headers: { 'Content-Type': 'application/json' } }
    )
  }
})

Type Generation

# Generate TypeScript types
npx supabase gen types typescript --project-id your-project-id > types/supabase.ts

# Use in code
import { Database } from '@/types/supabase'

type Item = Database['public']['Tables']['items']['Row']
type ItemInsert = Database['public']['Tables']['items']['Insert']
type ItemUpdate = Database['public']['Tables']['items']['Update']

Common Patterns

Soft Deletes

alter table public.items add column deleted_at timestamp with time zone;

create policy "Users cannot see deleted items"
  on public.items for select
  using (deleted_at is null);

-- Soft delete function
create or replace function soft_delete_item(item_id uuid)
returns void as $$
begin
  update public.items
  set deleted_at = now()
  where id = item_id;
end;
$$ language plpgsql security definer;

Audit Logs

create table public.audit_logs (
  id uuid default gen_random_uuid() primary key,
  created_at timestamp with time zone default now() not null,
  user_id uuid references auth.users(id),
  table_name text not null,
  record_id uuid not null,
  action text not null,
  changes jsonb
);

-- Trigger function
create or replace function public.audit_trigger()
returns trigger as $$
begin
  insert into public.audit_logs (user_id, table_name, record_id, action, changes)
  values (
    auth.uid(),
    TG_TABLE_NAME,
    NEW.id,
    TG_OP,
    to_jsonb(NEW) - to_jsonb(OLD)
  );
  return NEW;
end;
$$ language plpgsql security definer;

Troubleshooting

Common Issues

1. 401 Errors: Check RLS policies, ensure user is authenticated
2. 403 Errors: RLS policy blocking operation
3. Row not found: Policy may be filtering it out
4. Connection issues: Check URL and API keys
5. Type mismatches: Regenerate types after schema changes

Debugging RLS

-- Test as specific user
set request.jwt.claims = '{"sub": "user-uuid-here"}';

-- Check what policies apply
select * from pg_policies where tablename = 'items';

-- Disable RLS temporarily (for testing only!)
alter table public.items disable row level security;

Best Practices Checklist

• Enable RLS on all tables with user data
• Create indexes for foreign keys and frequently queried columns
• Use UUID for primary keys
• Add created_at and updated_at timestamps
• Implement soft deletes for important data
• Use check constraints for enum-like fields
• Generate and use TypeScript types
• Test RLS policies thoroughly
• Use service role key only server-side
• Implement proper error handling
• Add audit logs for sensitive operations
• Use transactions for multi-step operations

When to Use This Skill

Invoke this skill when:

• Designing database schemas
• Creating or debugging RLS policies
• Setting up authentication
• Building Edge Functions
• Implementing real-time features
• Troubleshooting Supabase issues
• Optimizing database queries
• Setting up type generation