MVCC (Multi-Version Concurrency Control) yaiku carane PostgreSQL nangani akses bebarengan — tinimbang ngunci baris kanggo baca, iku tetep macem-macem versi saka baris, mula saben transaksi katon snapshot konsisten saka data. Keuntungan utama: sing maca ora ngalangi sing nulis, lan sing nulis ora ngalangi sing maca, mbukak concurrency dhuwur.
Ide pokok: macem-macem versi baris
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.
