OK, first my simple Domain Model is 2 classes with a one-to-many relationship, a simple Parent -> child relationship. A 'Tweet' has one or more 'Votes', but each Vote belongs to just one Tweets etc.
public class Tweet
{
public virtual long Id { get; set; }
public virtual string Username { get; set; }
public virtual string Message { get; set; }
public virtual ISet<Vote> Votes { get; set; }
}
public class Vote
{
public virtual long Id { get; set; }
public virtual long TwitterUserId { get; set; }
public virtual DateTime VotedDate { get; set; }
public virtual Tweet Tweet { get; set; }
}
I'm trying to write a query in either HQL, ICriteria or NHibernate LINQ, that selects all Tweets, but also add two columns that selects:
- A count of the number of votes, and...
- Whether a particular user has voted for that tweet, based on a particular TwitterUserId
With the two extra columns, I'm not expecting to get Tweet domain object back, and would probably need to run a Report query, that's OK. But I'm struggling to figure out how to write this query.
I know how to write this as a Stored Procedure, or using LINQ 2 SQL. If it helps I will express this as a LINQ to SQL query.
long userId = 123;
var tweets = from t in dataContext.Tweets
where t.Application == app
orderby t.PostedDate desc
select new TweetReport()
{
Id = t.Id,
Username = t.Username,
Message = t.Message,
TotalVotes = t.Votes.Count(),
HasVoted = t.Votes.Any(v => v.TwitterUserId == userId)
};
I know this will work in LINQ 2 SQL, and generate reasonably efficient T-SQL, but I can't figure out how to write this in NHibernate.
Update: I tried running the above LINQ query in NHibernate by using the NHibernate LINQ provider built for NHibernate v2, eg:
var tweets = from t in Session.Linq<Tweet>()
where (snip)
But it didn't work. Has LINQ support in Nhibernate 3.0 improved? I'm a bit reluctant to use version 3.0 because it's still alpha, but if this will work, then I might give it a go.
Update 2: Thanks to Diego Mijelshon's suggestion, I upgraded to NHibernate 3.0 alpha 2 and wrote the query in LINQ:
var tweets = from t in Session.Query<Tweet>()
where t.App == app
orderby t.PostedDate descending
select t;
int totalRecords = tweets.Count();
var pagedTweets = (from t in tweets
select new TweetReport()
{
Id = t.Id,
TwitterId = t.TweetId,
Username = t.Username,
ProfileImageUrl = t.ImageUrl,
Message = t.Message,
DatePosted = t.PostedDate,
DeviceName = t.Device.Name,
DeviceUrl = t.Device.Url,
TotalVotes = t.Votes.Count(),
HasVoted = t.Votes.Any(v => v.TwitterUserId == userId)
})
.Skip(startIndex)
.Take(recordsPerPage)
.ToList();
return new PagedList<TweetReport>(pagedTweets,
recordsPerPage, pageNumber, totalRecords);