Save returns entity without really saving

[kschlesselmann]

After upgrading to Spring Boot 3.5.9 we saw some tests failing. It seems that there have been some changes that probably do not handle updates correctly.

e21cdd4#diff-e1718e663d72a945b1dc63ad8117fa9c5277d66a88d33e68c6e0a1269cc04f5eL686

Here is a small sample to reproduce the current behaviour: https://github.com/fortis-it-services/spring-data-relational-entity-save

Generally the ::save method of the repository is just returning the entity (even without actually doing anything because setting the ID results in an UPDATE instead of an INSERT) and suggesting that it saved something (by returning the value). If you later ask the repository for its data it's returning nothing.

[mp911de]

This sounds almost like #2209. Can we close this one as a duplicate? There's a bit of discussion on the other ticket.

[kschlesselmann]

@mp911de Currently it looks like that the discussion is about entities that could be updated because they actually exist.

If we're going to include this case here (where entities that do not exist aren't saved) in the discussion it's fine for me to merge these issues though.

[schauder]

While the two might be related, I don't think we should close this one, until we properly understand what is going on.