save() on an Existing Id Updates It

save() reads as though it always creates something new. Called on an entity that already has an id, it does the opposite.

java

RideEntity existing = repo.findById(id).orElseThrow();
existing.status = "completed";
repo.save(existing);

text

save() on existing id: count before=3 after=3 (same id updated, not inserted)

run in a container — the row count never changes

save() checks whether the entity's id is already set. If it is, Spring Data issues an UPDATE against that row instead of an INSERT — which is exactly the behaviour that makes "load, modify, save" the normal pattern for changing a row, rather than a separate update() method existing at all.

Spring Boot
Relational Databases