[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-2277) bidirectional <key-many-to-one> both lazy=false fetch=join lead to infinite loop

[Steve Ebersole (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-2277?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=37207#action_37207 ] 

Steve Ebersole commented on HHH-2277:
-------------------------------------

Actually 2-phase load will not even help here.  2-phase load still has an implied contract that the ids all be resolved up front.  And that is unfortunately the issue here.  In other words, given:
{noformat}
Customer( long id )
Order( PK id( Customer customer, long orderNumber ) )
{noformat}

The algorithm performed by Loader to read a row is
# read all keys from the result set
# read all values from the result set

In the problematic case, this means that it tries to:
# read the Order key from the result set
# read the Customer key from the result set
# read the Order values from the result set (using 2-phase load)
# read the Customer values from the result set (using 2-phase load)
(the order of Customer/Order here is irrelevant)

So in step (1) it is unable to resolve the Order key fully because Customer has not yet been processed.  Since it does not "see" the Customer it attempts to load it, which forces the Loader to basically just get called again (hence the infinite loop).

The other issue here with *just* having a 2-phase load for components is that the order in which these get processed from the result set now becomes important.

The only option I see is some form of "order aware" solution, where the Loader knows about the relationship between the persisters it is processing (it does sorta/kinda in that the order of the persisters returned by org.hibernate.loader.Loader#getEntityPersisters is semi-important).  Really what needs to happen here specifically is that Customer needs to be at least in a state where it has been added to the PersistenceContext in LOADING state prior to processing Order or its key.  This means, though, a pretty drastic change to the internals of Loader.

The thing to be aware of on the other side is to not "go too far" in processing Customer, specifically in resolving its associations, since those associations mey still be awaiting processing from the current result set.

> bidirectional <key-many-to-one> both lazy=false fetch=join lead to infinite loop
> --------------------------------------------------------------------------------
>
>                 Key: HHH-2277
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2277
>             Project: Hibernate Core
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 3.2.1
>            Reporter: Emmanuel Bernard
>            Assignee: Steve Ebersole
>             Fix For: cfg-rework
>
>


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