Override lazy loading behavior 'lazy=false'
I would like to override the default lazy loading behavior which is set in mappings as 'lazy=false'. Can't change it as many parts of existing application depend on this setting.
After spent some hours on it I didn't find a solution so I'm asking here. How to do this? What I want to achieve is to fine tune my query to load only what is needed. This is what I've tried already:
Using QueryOver api:
var properties = session.QueryOver<Property>() .Fetch(prop => prop.Transactions).Eager .Fetch(prop => prop.Districts).Eager //I dont want to load those entities below so I mark //them as lazy - IT DOESN'T WORK //I can see in SQL that they are getting loaded in separate queries .Fetch(prop => prop.Districts.First().Aliases).Lazy .Fetch(prop => prop.Districts.First().PolygonPoints).Lazy .Skip(i * pageSize) .Take(pageSize) .List();
Using Criteria api:
var criteria = session.CreateCriteria<Property>(); criteria.SetFetchMode("Transactions", NHibernate.FetchMode.Join); criteria.SetFetchMode("Districts", NHibernate.FetchMode.Join); criteria.SetFetchMode("Districts.Aliases", NHibernate.FetchMode.Select); // tried Lazy too criteria.SetFetchMode("Districts.PolygonPoints", NHibernate.FetchMode.Select); // tried Lazy too criteria.AddOrder(NHibernate.Criterion.Order.Asc("Id")); criteria.SetFirstResult(i * pageSize); criteria.SetMaxResults(pageSize); var properties = criteria.List<Property>();
Using any of the above methods 'Aliases' and 'PolygonPoints' are always being loaded when calling List<>(). I don't need them in my process.
I'm using Nhibernate 4.0. Any ideas?
We cannot override mapping in this case. We can do it opposite way - have lazy in place - and use eager fetching for querying.
The decision process (of reference loading) is done outside of the query, ex post. So it could be pre-loaded, but cannot be avoided.
Solution here could be of two types.
- The first is preferred (by me) - do your best and make laziness the default: Ayende - NHibernate is lazy, just live with it
- Use projections. Instruct NHibernate to create just one query, use transformer to get expected object graph - without any proxies in it
There is pretty clear example how to (properly) use projection list even for references:
And we would also need Custom result transformer, which will ex-post create all the references from the returned data:
- Custom DeepResultTransfomer