[hibernate-issues] [Hibernate-JIRA] Created: (HHH-2272) Serious performance problems when saving large amount of transient entities with collections of transient entities

[Markus Heiden (JIRA)]

Serious performance problems when saving large amount of transient entities with collections of transient entities
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         Key: HHH-2272
         URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2272
     Project: Hibernate3
        Type: Task

  Components: core  
    Versions: 3.2.0.ga    
 Environment: Hibernate 3.2.0 on Oracle 9.2
    Reporter: Markus Heiden


When saving many (e.g. 50000) transient entities with a collection of transient entities, for each collection element the whole persistence context is searched (by StatefulPersistenceContext#getIndexInOwner() and StatefulPersistenceContext#getOwnerId) and its even searched twice when the collection is an indexed collection. This leads to an enormous amount (> 1000000) of iterations over all entities and over all collection elements of each entity. Especially when one saves only the same type of entities this leads to times of hours(!) even on a fast machine before any insert statement is even issued. This issue is related to HHH-1612, but fixing issue HHH-1612 won't resolve this problem (I have explored this with a hack which fixes HHH-1612).

In my eyes there are two ways to solve this problem:
1) When cascading the save of a parent, the parent cascade can fill the persistence context with information about its collection elements. E.g. before cascading the save to a collection a parent can add  a (child, parent) pair to a map in the persistence context to avoid the above described iterations. Then a simple Map#get() would be sufficient in most cases to get the parent.
2) When cascading, the parent has to be passed with the cascaded (e.g. saved) element. But this is no good solution, because it affects some well known hibernate apis.

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