Not exactly what you want, but if you call Clear() on a collection, it
should delete all records with a single DELETE statement.
RP
On Tuesday, August 5, 2014 5:02:37 PM UTC+1, Stevie Shannon wrote:
>
> I've spent some time on this problem scouring resources online and a
> couple of books I have on NH; but I'm struggling to get to the bottom of it.
>
> Basically: I'm finding that cascading deletes is sending SQL with many
> individual deletes, i.e. the N+1 problem.
>
> I have three tables: User, UserAttribute and Attribute. Each User has many
> UserAttributes, each UserAttribute has one Attribute - represented by the
> following Maps:
>
> public UserMap() {
> Id(x => x.Id);
>
> Map(x => x.Description);
>
> HasMany(x => x.Attributes)
> .Inverse()
> .Cascade.AllDeleteOrphan();
> }
>
> public UserAttributeMap() {
> Id(x => x.Id);
>
> References(x => x.User)
> .Not.Nullable();
>
> References(x => x.Attribute)
> .Not.Nullable()
> .Cascade.All();
> }
>
> public AttributeMap() {
> Id(x => x.Id);
>
> Map(x => x.Name)
> .Unique();
> }
>
> The problem I'm experiencing is that when I delete a User entity, the
> cascade generates an individual delete for each UserAttribute and each
> Attribute; which is a potentially large performance problem (A User could
> typically have hundreds of Atributes).
>
> In the above test scenario my schema is then generated using FluentNH, I
> have an IdConvention setting all Ids to GuidComb and In addition to this, I
> have a repository that I go through to access the Session.SaveOrUpdate,
> Session.Delete, etc - each of which is wrapped in a Transaction.
>
> Is there something obviously wrong with the mapping that would be
> triggering the N+1 problem here? Is there anything I can do to stop it? Is
> this crazy talk?
>
> -------
>
> As a side note, my NHibernate configuration already includes a large batch
> size, but as far as I'm aware batching won't wrap up something like this?
> They certainly don't appear to be batched when I profile them.
>
> NHibernate v3.3.1.4000
> FluentNHibernate v 1.4.0.0
>
> UserTable:
> Id
> Description
>
> UserAttributeTable:
> Id
> User_id (FK)
> Attribute_id (FK)
>
> AttributeTable:
> Id
> Name
>
>
>
--
You received this message because you are subscribed to the Google Groups
"nhusers" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/nhusers.
For more options, visit https://groups.google.com/d/optout.
