Database & Migrations

• Always use the rails generate migration command to create migration files.
• Migrations must be reversible.
• Add null: false and database-level defaults where appropriate.
• Use text over string if length varies significantly.
• Wrap multi-record operations in transactions. Use save! (bang) inside transactions.
• Keep scopes as one-liners. Complex queries belong in search/query objects.
• Never use Post.all without pagination.
• Avoid .count in loops.
• Use counter_cache.