Help with a particular mapping scenario

[sed]

I am having problem find the best way to map a particular
relationship. We have a feature where people can follow other people.
Typically we would have a table People, like this

People-
PersonID
Name
Etc

A linking table is typically used that contains the Person being
followed ID and followerID.

We need to be able to be able to perform queries that would allow a
person to see who they follow, filter content by people who they
follow and view the users who follow them.

Has anyone else faced this kind of problem before?

[Paul Batum]

People usually refer to this as a self referencing many-to-many. I wrote a little sample of this earlier in the year. Perhaps it will help:

https://github.com/paulbatum/Fluent-NH-Test-Bed/tree/self-referencing-many-to-many

Here's the most important bit:

public class CustomerMap : ClassMap<Customer>
    {
        public CustomerMap()
        {
            Id(x => x.CustomerId);
            Map(x => x.Birthday);
            Map(x => x.FirstName);


            HasManyToMany(x => x.Parents)
                .ParentKeyColumn("ChildID")
                .ChildKeyColumn("ParentID")
                .Inverse();
            
            HasManyToMany(x => x.Children)
                .ParentKeyColumn("ParentID")
                .ChildKeyColumn("ChildID");
        }
    }

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[Nick Webb]

I am a little confused by your schema - do you have a single People object, each object representing a person, that links back to itself?  Or do you have a People object that links to a Person object?

I would suggest:

Person

 - Id

 - Name

 - [stuff!]

 - Followers (IList<Person>)

With Followers being a ManyToMany.  Then you could simply query against the property like anything else using a join:

"select p from Person p join p.Followers as Person f where p.Id = :personId and f.Name = :whatever"

[Nick Webb]

Beat me to it by seconds!

[sed]

Thanks, I have mapped this out and it seems good but querying is
really difficult.

I have any kind of random content we'll just called Content that
HasOne<Person>. I need to query Content and filter it to the Followees
list. Is that possible?

On Nov 19, 8:57 am, Nick Webb <nwe...@gmail.com> wrote:
> Beat me to it by seconds!
>
>
>
>
>
>
>
> On Fri, Nov 19, 2010 at 8:56 AM, Paul Batum <paul.ba...@gmail.com> wrote:
> > People usually refer to this as a self referencing many-to-many. I wrote a
> > little sample of this earlier in the year. Perhaps it will help:
>

> >https://github.com/paulbatum/Fluent-NH-Test-Bed/tree/self-referencing...
>
> > <https://github.com/paulbatum/Fluent-NH-Test-Bed/tree/self-referencing...>Here's

> >> fluent-nhibern...@googlegroups.com<fluent-nhibernate%2Bunsubscr i...@googlegroups.com>
> >> .

> >> For more options, visit this group at
> >>http://groups.google.com/group/fluent-nhibernate?hl=en.
>
> >  --
> > You received this message because you are subscribed to the Google Groups
> > "Fluent NHibernate" group.
> > To post to this group, send email to fluent-n...@googlegroups.com.
> > To unsubscribe from this group, send email to

> > fluent-nhibern...@googlegroups.com<fluent-nhibernate%2Bunsubscr i...@googlegroups.com>
> > .

[Nick Webb]

Just another join like any join.  Read up here.

Basically, your hql would be along the lines of:

"from Content content join Followees as person where person.Name [... your where clause here]"

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