supabase-common-errors

# Supabase Common Errors ## Overview Diagnostic guide for Supabase errors across PostgREST (`PGRST*`), PostgreSQL (numeric codes), Auth, Storage, and Realtime. Identify the error layer, trace the root cause, and apply the correct fix — every SDK call returns `{ data, error }` where `data` is null when `error` exists. ## Prerequisites - `@supabase/supabase-js` installed (`npm install @supabase/supabase-js`) - `SUPABASE_URL` and `SUPABASE_ANON_KEY` (or `SUPABASE_SERVICE_ROLE_KEY`) configured - Access to Supabase Dashboard (for log inspection and SQL Editor) - Supabase CLI installed for local development (`npx supabase --version`) ## Instructions ### Step 1 — Capture the Error Object Every Supabase SDK call returns a `{ data, error }` tuple. Never assume `data` exists — always check `error` first. ```typescript import { createClient } from '@supabase/supabase-js' const supabase = createClient( process.env.SUPABASE_URL!, process.env.SUPABASE_ANON_KEY! ) // WRONG — data is null when error exists const { data } = await supabase.from('todos').select('*') console.log(data.length) // TypeError: Cannot read property 'length' of null // CORRECT — always check error first const { data, error } = await supabase.from('todos').select('*') if (error) { console.error(`[${error.code}] ${error.message}`) console.error('Details:', error.details) console.error('Hint:', error.hint) // error.code tells you the layer: // PGRST* = PostgREST (API gateway) // 5-digit nume...