Hello,

Can you tell me what the merge() method looks at to decide whether an object needs to be updated.

In my application I'm seeing that *any* call to merge on one of my detached objects results in a SQL update call. Looking at the SQL call, it appears that every member of the object is being updated.

The pattern I see is as follows:

1. objects are instantiated (read in from the database) and held in a private collection
2. One of those objects is then 'merge()ed' - this is to ensure the object is not detached - this is necessary as it is very likely that the merge operation may be performed later in another thread.
3. Later at commit (or FlushtoDB() time), I see updates corresponding to the mappings defined in the annotations. (e.g. updates to the base tables, insert/delete operations to any join tables etc.).

The thing is, the application has not specifically updated any of these objects hence the reason for my question - what tells merge() that it needs to refresh the instance from the database?

-Thom

I don't really understand the question, can you provide a specific case/code and explain why you think this is not right?

Hello Emmanuel,

You misunderstand me - I'm not saying anything is broken!

What I'm seeking is an understanding off what steps the EntityManager performs to decide whether an entity should be updated following a merge request.

I have a situation here where I have some detached objects (that were fetched from a database) and I perform a merge on those objects. I'm noticing that everytime a merge call is made, an update of the database follows at commit time. I'm not explicitly changing the values of the objects in my application, but something must be as merge always creates some update statements following the merge call.

I strongly suspect that this is a bug in the application (not hibernate) but it would help a lot if you could briefly tell me what merge() looks at to decide whether an object needs updated in the database.

Thanks,

Thom

Hibernate check each value type (property / association) of a given entity and apply an isEqual algorithm
If one of them is not equal, then the object is considered dirty.

you can check type.isEqual() or userType.isEqual()

In your case, that's probably a getter or a setter that mess stuffs around