Backend process of UPDATE query in EDB/PostgreSQL

PostgreSQL UPDATE operations work through a multi-step process involving shared buffers, MVCC (Multi-Version Concurrency Control), and WAL (Write-Ahead Logging). When updating a row, PostgreSQL creates a new version rather than modifying in place, marks pages as dirty in memory, generates WAL records for durability, and only commits the transaction once WAL records are safely written to disk. This architecture ensures data consistency, enables concurrent access, and provides crash recovery capabilities.