[xwiki-devs] New "Foreign Key" property - xwiki-devs@xwiki.org

Pascal Voitot

24 Oct 24 Oct

12:51 a.m.

I had the same idea a few weeks ago. But my idea was not only to allow using foreign key but to create directly a "BaseObjectProperty" which would be represented by a foreign key in the DB but which would be mapped in HQL as a BaseObject... Something like: "select obj.linkedobj from BaseObject as obj" This would be really really powerful... I have been linking 2 objects using a LongProperty to represent the foreign key but I can't write direct HQL requests... regards Pascal On Thu, Oct 23, 2008 at 5:11 PM, Thomas McColgan < thomas.mccolgan(a)googlemail.com> wrote:

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I'm proposing to implement a new property type: A foreign key, analogous to the concept in relational databases. Together with custom mapping, a property like this would make it possible to use Xwiki as a frontend for a relational database, while making full use of the wikis capabilities(configurability, history, etc). The implementation would look similar to the existing "Database list" on the outside, but it would make a lot more use of the databases features. If A links to B, and someone deletes B the reference in A would either be set to null, or the delete would be stopped, depending on the configuration. It would also make it possible to adress associated objects directly in hql. The basic functionality can be emulated using DBList(adding a property to one object by choosing from existing instances of another class), but this is not useful if one wants to have "real" foreign key behaviour in the wiki and the underlying DB. If there is a demand for this I will be happy to contribute a patch once I am done, and I will try make the code nice enough to submit. Otherwise I will probably just make it as a hack to meet the exact need that I have... Thomas _______________________________________________ devs mailing list devs(a)xwiki.org http://lists.xwiki.org/mailman/listinfo/devs

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Pascal Voitot

25 Oct 25 Oct

1:03 p.m.

fully agree with that! if need any support, don't hesitate to ask... will try to find a few minutes... On Fri, Oct 24, 2008 at 6:20 AM, Artem Melentyev <amelentev(a)gmail.com>wrote;wrote:

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Hi, Thomas. I think it is a good idea. It would be very useful for xwiki. I propose ReferencePropertyClass (contains reference target (object,document,attachment), cascade delete options and other configurations) ObjectReferenceProperty (reference to BaseObject) DocumentReferenceProperty (if needed. reference to XWikiDocument) as name of these properties. I think "Foreign key" is too technical name for this. Please create a jira issue (new feature) and attach patches. Thanks Thomas McColgan wrote:

I'm proposing to implement a new property type: A foreign key, analogous to the concept in relational databases. Together with custom mapping, a property like this would make it possible to use Xwiki as a frontend for a relational database, while making full use of the wikis capabilities(configurability, history, etc). The implementation would look similar to the existing "Database list" on the outside, but it would make a lot more use of the databases features. If A links to B, and someone deletes B the reference in A would either be set to null, or the delete would be stopped, depending on the configuration. It would also make it possible to adress associated objects directly in hql. The basic functionality can be emulated using DBList(adding a property to one object by choosing from existing instances of another class), but this is not useful if one wants to have "real" foreign key behaviour in the wiki and the underlying DB. If there is a demand for this I will be happy to contribute a patch once I am done, and I will try make the code nice enough to submit. Otherwise I will probably just make it as a hack to meet the exact need that I have... Thomas _______________________________________________ devs mailing list devs(a)xwiki.org http://lists.xwiki.org/mailman/listinfo/devs

-- Artem Melentyev _______________________________________________ devs mailing list devs(a)xwiki.org http://lists.xwiki.org/mailman/listinfo/devs

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Pascal Voitot

28 Oct 28 Oct

3:36 p.m.

Don't understand exactly what's your problem? you can't cascade delete? On Mon, Oct 27, 2008 at 5:00 PM, Thomas McColgan < thomas.mccolgan(a)googlemail.com> wrote:

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OK, I am slowly getting there. The status now is that it defaults to setting the value to null if the "parent" is deleted. The best thing would be if it was possible to have a cascade delete and maybe even refuse behavior, too. I'm not sure how to implement that, though... I don't even know if that is possible without a big rewrite. I guess I would need a kind of hook into the deleting routine of all objects... Any ideas? Thomas On Sat, Oct 25, 2008 at 12:03 PM, Pascal Voitot <pascal.voitot.dev(a)gmail.com> wrote:

fully agree with that! if need any support, don't hesitate to ask... will try to find a few minutes... On Fri, Oct 24, 2008 at 6:20 AM, Artem Melentyev <amelentev(a)gmail.com wrote:

Hi, Thomas. I think it is a good idea. It would be very useful for xwiki. I propose ReferencePropertyClass (contains reference target (object,document,attachment), cascade delete options and other configurations) ObjectReferenceProperty (reference to BaseObject) DocumentReferenceProperty (if needed. reference to XWikiDocument) as name of these properties. I think "Foreign key" is too technical name for this. Please create a jira issue (new feature) and attach patches. Thanks Thomas McColgan wrote:

I'm proposing to implement a new property type: A foreign key, analogous to the concept in relational databases. Together with custom mapping, a property like this would make it possible to use Xwiki as a frontend for a relational database, while making full use of the wikis capabilities(configurability, history, etc). The implementation would look similar to the existing "Database list" on the outside, but it would make a lot more use of the databases features. If A links to B, and someone deletes B the reference in A would either be set to null, or the delete would be stopped, depending on the configuration. It would also make it possible to adress associated objects directly in hql. The basic functionality can be emulated using DBList(adding a property to one object by choosing from existing instances of another class), but this is not useful if one wants to have "real" foreign key behaviour in the wiki and the underlying DB. If there is a demand for this I will be happy to contribute a patch once I am done, and I will try make the code nice enough to submit. Otherwise I will probably just make it as a hack to meet the exact need that I have... Thomas _______________________________________________ devs mailing list devs(a)xwiki.org http://lists.xwiki.org/mailman/listinfo/devs

-- Artem Melentyev _______________________________________________ devs mailing list devs(a)xwiki.org http://lists.xwiki.org/mailman/listinfo/devs

_______________________________________________ devs mailing list devs(a)xwiki.org http://lists.xwiki.org/mailman/listinfo/devs

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