MTAR T3D Sessions: The Hidden Cost of Default Values in Postgres

Adding a column with a default value feels like a safe change. It is fast, avoids locking, and keeps things moving. But in Postgres, that speed comes from a tradeoff that can quietly affect performance later.Brian Fehrle, Database Administrator at Command Prompt, explains how Postgres handles these defaults without writing them to disk, and why that can leave the query planner working with incomplete information.In this episode, a real production case shows how queries that were once fast suddenly slowed down after a schema change, and how fixing it required more work than expected. It is a small decision with consequences that only show up when the system is under pressure.