[jira] [Commented] (JDO-660) Ability to specify positioning of field 'column(s)' in datastore "table"

["Craig L Russell (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/JDO-660?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13474765#comment-13474765 ] 

Craig L Russell commented on JDO-660:
-------------------------------------

I've updated chapters 15, 18, and 19 to reflect this change.

The semantics were added to 18.4:

The position attribute specifies the relative position of the column when generating schema for the table. Columns are defined in the order as specified by the position attribute, with 0 being the first column defined. Columns with no position attribute (default, or with a value of -1), are defined at the end of the table. Columns with the same position attribute are defined together but with an arbitrary relative position. 
                
> Ability to specify positioning of field 'column(s)' in datastore "table"
> ------------------------------------------------------------------------
>
>                 Key: JDO-660
>                 URL: https://issues.apache.org/jira/browse/JDO-660
>             Project: JDO
>          Issue Type: New Feature
>          Components: api, specification, tck
>            Reporter: Andy Jefferson
>            Assignee: Craig L Russell
>             Fix For: JDO 3 maintenance release 1 (3.1)
>
>         Attachments: column_position.patch
>
>
> With an RDBMS datastore, when generating the schema, it is desirable to be able to specify the positioning of the column(s) of a field in the generated table. 
> With spreadsheet documents, it is critical to be able to define which column number is used for a particular field.
> With other datastores it is also likely desirable.
> To achieve this I propose adding an attribute to the XML <column> called "position". Similarly for the @Column annotation.
> This can take integer values with 0-origin.
> Complications : 
> 1. how this is handled when we have inheritance. If a root class has subclass-table inheritance, then those fields are persisted into the tables of all subclasses, and we may want to override the positions for those individually - to that end the user can override the metadata of the superclass fields. 
> 2. anything else ?

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