Question

public IEnumerable<UserReadNews> GetLatestUserReadNews(IEnumerable<string> userIds)
{

    IQuery query = Session.CreateQuery("from UserReadNews as j where j.FacebookUser_id in (:userIds)");
    query.SetParameterList("userIds", userIds );
    return query.List();
}

I have this method where I want to return this data as lazily as possible, because I am determining which data to show and then stopping. I don’t want the whole query to be executed against the whole table.

My concern is the List() method. is this lazy or eager?

Can I call this method from another method and yield break when I’m done with what I need?

Answer 1

I agree with @CSharper about only querying what you absolutely need.

If you still need to make this as lazy as possible after that optimization, use ICriteria.Future<T>() instead of ICriteria.List<T>():

public IEnumerable<UserReadNews> GetLatestUserReadNews(IEnumerable<string> userIds)
{
    IQuery query = Session.CreateQuery("from UserReadNews as j where j.FacebookUser_id in (:userIds)");
    query.SetParameterList("userIds", userIds );
    return query.Future<UserReadNews>();
}

Future will give you an actual IEnumerable with deferred querying instead of a whole list right off the bat. It will sometimes optimize queries too when given the chance.