You are correct in that the schema does not _have_ to be completely static.
However, NH works better with static schemas, so it might not be the correct
tool to use in those cases.
But of course there's nothing wrong in _mixing_ it with other approaches.
Diego
On Thu, Oct 14, 2010 at 04:21, Gunnar Liljas <[email protected]>wrote:
> I agree that modifying the database schema at runtime is usually a bad
> idea, but having implemented more EAV systems than I can remember, I'm
> starting to think that maybe we shouldn't treat the schema as
> something holy. Or, at least we could maybe have a relaxed attitude
> for one or a couple of tables in our database, which we treat
> differently. The performance gain and reduced query complexity can be
> worth it. The trick is just to be careful.
>
> Of course, a more unstructured storage of "user defined entities" is
> also feasible, e.g storing the objects as a serialized blob (or XML).
> Indexing and querying can be dealt with. Maybe not by the DBMS, but by
> adding external indexing, e.g with Lucene.
>
> /G
>
>
>
>
> On Wed, Oct 13, 2010 at 7:42 AM, pvginkel <[email protected]> wrote:
> > I would think that this strategy would make upgrading the databases to
> > a new version of your application a living hell. What happens when a
> > new version of your application adds a field to a table that a client
> > added himself?
> >
> > What do you need this facility for? If it's just to allow your clients
> > to add free form information to tables, adding a generic mechanism,
> > similar to EAV [http://en.wikipedia.org/wiki/Entity-attribute-
> > value_model] to your database schema would probably be a better idea.
> >
> > It looks like "Implementing and indexing User Defined Fields in an SQL
> > DB" [http://stackoverflow.com/questions/1600811/implementing-and-
> > indexing-user-defined-fields-in-an-sql-db] describes what you're
> > trying to do.
> >
> > This would also solve the issue of your objects being out of date with
> > your schema.
> >
> > On Oct 12, 5:50 am, foxprorawks <[email protected]> wrote:
> >> Hi,
> >>
> >> We are currently evaluating various technologies and designing our new
> >> product.
> >>
> >> Our new product will include multi-tenancy. Each customer will be
> >> supplied with a standard database, but the system will allow users to
> >> modify the database (by adding or removing fields from existing
> >> tablesor adding totally new tables). Each customer will have their
> >> own separate database.
> >>
> >> The database modification will be done via a web interface.
> >>
> >> We are looking at MVC2 and NHibernate 2.
> >>
> >> This is the first time we've used either technology, so it's a steep
> >> learning curve for us.
> >>
> >> We've read some interesting ideas, particularly on the Ayende site:
> >>
> >> http://ayende.com/Blog/archive/2009/04/11/nhibernate-mapping-ltdynami.
> ..
> >>
> >> One question we have is, can the data model be easily updated at
> >> runtime to match the new fields added by customers?
> >>
> >> Also, how do we get the application to use separate data models for
> >> each customer (although each customer will have a separate database,
> >> they will all be served by the same application which will determine
> >> which database to connect to)?
> >>
> >> Regards.
> >>
> >> Matt.
> >
> > --
> > You received this message because you are subscribed to the Google Groups
> "nhusers" group.
> > To post to this group, send email to [email protected].
> > To unsubscribe from this group, send email to
> [email protected]<nhusers%[email protected]>
> .
> > For more options, visit this group at
> http://groups.google.com/group/nhusers?hl=en.
> >
> >
>
> --
> You received this message because you are subscribed to the Google Groups
> "nhusers" group.
> To post to this group, send email to [email protected].
> To unsubscribe from this group, send email to
> [email protected]<nhusers%[email protected]>
> .
> For more options, visit this group at
> http://groups.google.com/group/nhusers?hl=en.
>
>
--
You received this message because you are subscribed to the Google Groups
"nhusers" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/nhusers?hl=en.
