Database Migration Skill

Supabase migration patterns, RLS audit, schema validation. Guides safe DDL operations against the Supabase database.

When to Activate

• •Invoke with /db-migration
• •When creating SQL migrations
• •When modifying table schemas or RLS policies

Migration File Location

• •backend/supabase/migrations/YYYYMMDD_description.sql

Pre-Migration Checklist

1. •Test SQL in dev environment first (use mcp__supabase__execute_sql)
2. •Verify no breaking changes to existing RPC functions
3. •Check RLS impact on existing queries
4. •Verify key access patterns — service_role (backend) vs anon (frontend)
5. •Run advisors after migration — mcp__supabase__get_advisors for security + performance

Safe Patterns

-- Always use IF NOT EXISTS / IF EXISTS
CREATE TABLE IF NOT EXISTS my_table (...);
CREATE INDEX IF NOT EXISTS idx_name ON my_table (column);
DROP TABLE IF EXISTS old_table;

-- Wrap multi-statement migrations
BEGIN;
  ALTER TABLE my_table ADD COLUMN new_col TEXT;
  CREATE INDEX idx_new ON my_table (new_col);
COMMIT;

-- Add comments explaining purpose
COMMENT ON TABLE my_table IS 'Description of table purpose';

RLS Audit Patterns

• •Every new table MUST have RLS enabled: ALTER TABLE my_table ENABLE ROW LEVEL SECURITY;
• •Verify policies cover: SELECT, INSERT, UPDATE, DELETE
• •Backend uses service_role key (bypasses RLS)
• •Frontend uses anon key (subject to RLS)
• •After adding RLS, test with both keys

MCP Tools Available

Anti-Patterns (BLOCK)

• •DROP TABLE without backup/confirmation
• •ALTER TABLE with data loss potential (dropping columns with data)
• •Disabling RLS on tables with user data
• •Running DDL directly via execute_sql (use apply_migration for audit trail)
• •Missing IF NOT EXISTS on CREATE statements
• •Forgetting to add RLS policies on new tables