[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-1296) Non lazy loaded List updates done in wrong order, cause exception

[Gail Badner (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-1296?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_29691 ] 

Gail Badner commented on HHH-1296:
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The patch is really not appopriate. There should be a constraint on child ID in the link table for a one-to-many association. I you require that a child be in a collection more than once, or in multiple collections, then the collection should be mapped as many-to-many.

There is definitiely a bug in how Hibernate updates rows after a deleting an element of a collection mapped as one-to-many. This issue will be fixed by HHH-3160.

The workaround mentioned in HHH-3160 is:

"For one-to-many list associations on a foreign key, the workaround is to define the unique constraint on (owner_id, position) in the child entity table as deferred. It is assumed that the primary key in the child entity table is the child ID.

For a one-to-many list association on a join table, the workaround is to define the constraint on (child_id) in the join table as deferred. It is assumed that the primary key in the join table is (owner_id, position).

If your Dialect does not support deferred constraints, then the only workaround is to exclude the unique constraint."


> Non lazy loaded List updates done in wrong order, cause exception
> -----------------------------------------------------------------
>
>                 Key: HHH-1296
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1296
>             Project: Hibernate3
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 3.0.5
>         Environment: Hibernate 3.0.5 - any database (checked postgres 7/8, mysql 4 & 5, db2 v8)
> NOT using lazy loading - the tx's are wrapped by session beans, so lazy loading is not allowed.
>            Reporter: David Birch
>            Assignee: Diego Pires Plentz
>            Priority: Critical
>         Attachments: listupdate_patch.txt, listupdate_patch.txt, listupdate_testcase.zip
>
>
> The logic behind list updates is not quite right, nor was it in v2 (only now i have a DBA who won't let up...)
> The scenario is:
> a bean with list property, and the list has a number of items in it (say 4, index 0-3), an item is then removed (say item at index 2), and the bean is requested to be saved.
> From what i can see in the SQL traces, the same statements are issues whe lazy loading is on or off, they are:
> [18/12/05 19:48:50:766 EST] 00000036 SystemOut     O Hibernate: delete from TGE_CLIENT_POLICY where CLIENT_ID=? and POSITION=?
> [18/12/05 19:48:50:766 EST] 00000036 SystemOut     O Hibernate: update TGE_CLIENT_POLICY set POLICY_NK=? where CLIENT_ID=? and POSITION=?
> So, i can only assume (as when this fails, the row with index 1 above the removed row is nuked!), hibernate removes the item at index 3, and then copies the value of the item at index 3 onto the row for item at index 2. Fair enough but...
> When i have lazy loading off, i get DB exceptions like
> Duplicate key or integrity constraint violation message from server: "Duplicate entry '1-999999' for key 1"
> so, there is some nasty in there, which is not updating the correct row - this has happened since 2.1.8 that i know of :(
> i will try & look @ the source, but won't get a chance until after xmas...

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