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Date: Wed, 3 Mar 2010 17:56:27 +0000 (UTC)
From: "Jeremy Bauer (JIRA)" <jira@apache.org>
To: dev@openjpa.apache.org
Subject: [jira] Commented: (OPENJPA-1074) OrderColumn does not maintain
 index upon inter-list element removal
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    [ https://issues.apache.org/jira/browse/OPENJPA-1074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12840762#action_12840762 ] 

Jeremy Bauer commented on OPENJPA-1074:
---------------------------------------

I fixed the non-spec compliant behavior described in this JIRA (ie. phase 1 - Per the latest JPA 2.0 spec, a contiguous index value must be maintained.) but the second phase of the JIRA has not been addressed:

"The current reordering mechanism does a full delete and reinsert of the container/collection table values if a reorder is required for inserts. For deletes, it just removes entries and leaves an empty index value. The first phase of the fix will be to maintain contiguous ordering using the same mechanism as inserts (delete/re-insert). The second phase will be to update the ChangeTracker to record the indexes of the updated list items and to use that information to provide a more intelligent update strategy in the handlers."

A more spec related side effect of OpenJPA's current order column update strategy is that the OrderColumn insertable and updatable attributes may not result in the behavior one may expect since the db operations used to maintain the list do not exactly map to the db operations indicated by these attributes.

I spent a few days looking into implementing phase 2, but it turned into a non trivial exercise.


> OrderColumn does not maintain index upon inter-list element removal
> -------------------------------------------------------------------
>
>                 Key: OPENJPA-1074
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-1074
>             Project: OpenJPA
>          Issue Type: Bug
>          Components: jdbc
>    Affects Versions: 2.0.0-M2
>            Reporter: Jeremy Bauer
>            Assignee: Jeremy Bauer
>            Priority: Critical
>             Fix For: 2.0.0
>
>
> The current order column reordering mechanism does not maintain a contiguous index value when an item is deleted from anywhere except the end of a collection.  Per the latest JPA 2.0 spec, a contiguous index value must be maintained.
> The current reordering mechanism does a full delete and reinsert of the container/collection table values if a reorder is required for inserts.  For deletes, it just removes entries and leaves an empty index value.  The first phase of the fix will be to maintain contiguous ordering using the same mechanism as inserts (delete/re-insert).  The second phase will be to update the ChangeTracker to record the indexes of the updated list items and to use that information to provide a more intelligent update strategy in the handlers.

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