MVCC (Multi-Version Concurrency Control) hija kif PostgreSQL tiddawwal ma' l-aċċess konkorrenti — minflok ma tiegħel ir-rittings għal qari, tżomm verżjonijiet multipli ta' rittings, biex kull transazzjoni taraSnapshot konsistenti tal-data. Il-benefiċcju ewlieni: qari ma jiġiex ibblokkat minn kittieba, u kittieba ma jibblokkaxxux qura, u dan jippermetti konkoranza għolja.
L-idea ewlenija: verżjonijiet multipli ta' rittings
When a row is UPDATED, Postgres doesn't overwrite it — it creates a NEW version and
marks the old one obsolete. Different transactions can see different versions.
→ Each transaction sees a consistent SNAPSHOT of the database as of its start
(depending on isolation level), unaffected by others' uncommitted changes.
