NHibernate Lazy=”Extra”

nhibernate

Is there a good explanation out there on what exactly lazy="extra" is capable of?

All the posts I've seen all just repeat the fact that it turns references to MyObject.ItsCollection.Count into select count(*) queries (assuming they're not loaded already).

I'd like to know if it's capable of more robust things, like turning MyObject.ItsCollection.Any(o => o.Whatever == 5) into a SELECT ...EXISTS query.

Section 18.1 of the docs only touches on it. I'm not an NH developer, so I can't really experiment with it and watch SQL Profiler without doing a bit of work getting everything set up; I'm just looking for some sort of reference describing what this feature is capable of.

Thank you!

Best Answer

for version 2.x it is only used to translate a collection.Count() into a select count and as far as i can see in the source, it will also allow the construct collection[5] to fetch that particular entity (with index 5) instead of hydrating the whole collection.

For version 3.x i didn't see anything related in the release notes

Related Solutions

JSON.NET and nHibernate Lazy Loading of Collections

I was facing the same problem so I tried to use @Liedman's code but the GetSerializableMembers() was never get called for the proxied reference. I found another method to override:

  public class NHibernateContractResolver : DefaultContractResolver
  {
      protected override JsonContract CreateContract(Type objectType)
      {
          if (typeof(NHibernate.Proxy.INHibernateProxy).IsAssignableFrom(objectType))
              return base.CreateContract(objectType.BaseType);
          else
              return base.CreateContract(objectType);
      }
  }

R – Best way to implement functionality similar to lazy=“extra” using NHibernate 2.0.1

When you say its a performance problem for other users, do you mean they also want to access the collection, but its too large for them. Or is the code snippet/ChildCollectionCount too slow for them?

If its the first case, then perhaps you need to do a similar solution for them - identify exactly what they need and provide methods that offer that facility.

Best Answer

Related Solutions

JSON.NET and nHibernate Lazy Loading of Collections

R – Best way to implement functionality similar to lazy=“extra” using NHibernate 2.0.1

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