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From "Ravi P Palacherla (JIRA)" <j...@apache.org>
Subject [jira] Created: (OPENJPA-1163) Data consistency issues while modifying collections.
Date Wed, 08 Jul 2009 15:33:14 GMT
Data consistency issues while modifying collections.
----------------------------------------------------

                 Key: OPENJPA-1163
                 URL: https://issues.apache.org/jira/browse/OPENJPA-1163
             Project: OpenJPA
          Issue Type: Bug
    Affects Versions: 2.0.0
         Environment: openJPA trunk. Derby DB.
            Reporter: Ravi P Palacherla
            Assignee: Ravi P Palacherla


There are data consistency issues when modifying more number of elements in a collection Vs
less number of elements.

Following is a detailed explanation about the issue with example:
 
- Entity A has a collection of Entities AItems with cascade ALL.
- Test case :
  Clear all the data inside tables representing Entity A and AItems.  
  Create 3 entity managers em1,em2 and em3.
   
  em1.begin()
      create A on em1 with id "1"
      add 10 elements of AItems (id's from 0-9) to the created A(id 1).
      persist A.
  em1.commit()
 
  em1.begin()
      merge A ( created in the previous step)
      Remove 3 elements of AItems from the merged A.
      Add 3 elements of AItems ( id's 10,11,12) to the merged A (id 1).
   
With out committing em1
   
  em2.begin()
      query database to fetch A and construct object result2 of entity A.
      Add 3 elements of AItems ( id's 13,14,15) to fetched A ( result2)      

   em2.commit ()
   em1.commit()
   
  em3.begin()
     query database to check the size of AItems that are related to A ( id 1)
  em3.commit()
   
  The result on em3's query for AItems related to A, returns 13 as expected.
  13 ( Initial 10 - em1's 3 + em1's 3 + em2's 3).
   
When the same test case is repeated with removing and adding 10 elements instead of 3 as before
then I get wrong results.
   
    Add initial 10 AItems (id's 0-9) for A.
    commit()
   
    em1 will remove 10 AItems from the collection of A.
    em1 will add 10 AItems (id's 10-19) to collection of A.
   
    em2 will add 10 AItems (id's 20-29) to collection of A.
   
    Commit em2.
    Commit em1.
   
    Then instead of 20 elements ( Initial 10 - em1's 10 + em1's 10 + em2's 10), I see only
10 elements.
   
    The 10 elements that I see are from em1's added AItems ( id's 10-19).


I think the cause of the issue is that, when more number of elements (compared to initial
element count of collection) in a collection are modified then collection tracking is disabled
and openJPA tries to do the following:
 -- Delete every thing from the collection
 -- Insert data back to collection.
While Inserting the data back it does not consider adding the dirty records ( em2's 10 added
elements ) because the collection tracking is disabled.

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