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The Object-Relational Powerhouse - PostgreSQL
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MVCC and Autovacuum
Postgres uses a system called Multi-Version Concurrency Control (MVCC) to handle simultaneous users. When you update a row in Postgres, it doesn't delete the old row immediately. Instead, it marks the old row as "dead" and creates a new version.
- The Issue (Bloat): Over time, these "dead rows" accumulate, taking up disk space and slowing down queries. This is known as Table Bloat.
- The Solution (Autovacuum): Postgres has a background process called the autovacuum daemon. A DBA must ensure this daemon is running and configured correctly. It automatically cleans up dead rows and updates the statistics that the Query Planner uses to make decisions.