I need to do a subquery on a sub collection but I can't get it to work.
I tried this
Task tAlias = null;
List<Task> result = session.QueryOver<Task>(() => tAlias)
.Where(Restrictions.In(Projections.Property(() => tAlias.Course.Id), courseIds))
.WithSubquery.WhereExists(QueryOver.Of<CompletedTask>().Where(x => x.Student.StudentId == settings.StudentId))
().ToList();
Yet I get
Cannot use subqueries on a criteria
without a projection.
session.QueryOver<Task>(() => tAlias)
.WhereRestrictionsOn(x => x.Course.Id).IsIn(courseIds)
.WithSubquery.WhereExists(QueryOver.Of<CompletedTask>()
.Where(x => x.id == tAlias.id) //not sure how you need to link Task to CompletedTask
.Where(x => x.Student.StudentId == settings.StudentId)
.Select(x => x.id)) //exists requires some kind of projection (i.e. select clause)
.List<Task>();
or if you only want the completedtask then just...
Task taskAlias = null;
session.QueryOver<CompletedTask>()
.JoinAlias(x => x.Task, () => taskAlias)
.WhereRestrictionsOn(() => taskAlias.Course.Id).IsIn(courseIds)
.Where(x => x.Student.StudentId == settings.StudentId)
.List<CompletedTask>();
or look into setting up a student filter on the Task.CompletedTasks collection. I've never used this feature before. I believe you have to enable the filter and set the student parameter before you run the query. Then your Task object would only contain completedTasks by that student...
http://nhibernate.info/doc/nh/en/index.html#filters
Related
For example:
Tree treeAlias = null;
var nonRottenApples = QueryOver.Of<Apple>()
.Where(a => !a.IsRotten)
.Where(a => a.Tree.Id == treeAlias.Id)
.Select(x => x.Id); // <- optional
return NHibernateSession.QueryOver(() => treeAlias)
.Where(t => t.Id.IsIn(ListOfTreeId))
.WithSubquery.WhereExists(nonRottenApples)
.List();
How do SubQuery not collection in Apple ?
I'm researching at various locations, but i not find results for my question.
All results are collections.
My interpretation of your question is that you're trying to query for the trees that don't have rotten apples.
I believe this will work:
var rottenTreeIds = QueryOver.Of<Apple>()
.Where(apple => apple.IsRotten)
.Select(a => a.Tree.Id);
return NHIbernateSession.QueryOver<Tree>()
.Where(t => t.Id.IsIn(ListOfTreeId))
.WithSubquery.WhereProperty(t => t.Id).NotIn(rottenTreeIds)
.List();
Invoking the following query when there is no Entity record in the database throws a NotSupportedException
var list = session.Query<Entity>()
.OrderBy(x => x.TranslationTime)
.Take(10)
.Select(x => x.TranslationTime)
.ToList();
Removing the Select(x => x.TranslationTime) makes the query be processed fine.
Is there a way to make NHibernate accept the original query even on empty result sets?
The Take(10) method has to come after the Select method:
var list = session.Query<Entity>()
.OrderBy(x => x.TranslationTime)
.Select(x => x.TranslationTime)
.Take(10)
.ToList();
I'm trying to write a query which returns randomly ordered results. I've found this post Linq Orderby random ThreadSafe for use in ASP.NET which gave me some basic clue how to do that. But i'm getting following exception:
variable 'x' of type 'Accomodations.DAL.Model.Generated.Accomodation' referenced from scope '', but it is not defined
Here is my query:
var query = session.QueryOver<Accomodation>()
.OrderBy(x => (~(x.Id & seed)) & (x.Id | seed)).Asc; // this is the problematic line of code
if (searchParams.District != 0)
query = query.Where(x => x.District.Id == searchParams.District);
if (searchParams.Region != 0)
query = query.Where(x => x.Region.Id == searchParams.Region);
if (searchParams.Location != 0)
query = query.Where(x => x.Location.Id == searchParams.Location);
var futureCount = query.Clone().Select(Projections.RowCount()).FutureValue<int>();
SearchAccomodationResultItem resultItemAlias = null;
var futurePage = query
.SelectList(list => list
.Select(x => x.Id).WithAlias(() => resultItemAlias.Id)
.Select(x => x.AccomodationType.Id).WithAlias(() => resultItemAlias.AccomodationTypeId)
.Select(x => x.Region.Id).WithAlias(() => resultItemAlias.RegionId)
.Select(x => x.Name).WithAlias(() => resultItemAlias.Title)
.Select(x => x.MaxCapacity).WithAlias(() => resultItemAlias.MaxCapacity)
.Select(x => x.MinPrice).WithAlias(() => resultItemAlias.MinPrice)
.Select(x => x.MinStayLength).WithAlias(() => resultItemAlias.MinStayLength)
.Select(x => x.MainImageName).WithAlias(() => resultItemAlias.ImgSrc)
)
.TransformUsing(Transformers.AliasToBean<SearchAccomodationResultItem>())
.Skip(skip)
.Take(searchParams.PageSize)
.Future<SearchAccomodationResultItem>();
searchResults = futurePage.ToList();
numberOfResults = futureCount.Value;
});
Any suggestion will be appreciated. Thanks
Here is a good example of how to do this. This is a technique that I'm currently using.
http://puredotnetcoder.blogspot.com/2011/09/nhibernate-queryover-and-newid-or-rand.html
Edit
Below is taken from the above article and I've modified it slightly to include Skip as well.
public IList<CmsTestimonial> GetRandomTestimonials(int count, int skip) {
return Session
.QueryOver<CmsTestimonial>()
.OrderByRandom()
.Take(count)
.Skip(skip)
.List();
}
To use the above approach with paging, you could store the seed for the user (on a per session basis probably) and then use the RAND(seed) function in SQL - because you use the same seed, it will generate the same sequence of pseudo-random numbers and thus allow paging
I've an associated entity with <many-to-one> and that entity has two <many-to-one> that I want to fetch at once. I can achieve this by this query:
var tshead = session.Query<MainEntity>()
.Fetch(r=>r.FirstAssoc).ThenFetch(p=>p.Other)
.Fetch(r=>r.FirstAssoc).ThenFetch(p=>p.Another)
.Take(10)
.ToList();
As you can see I had to wrote twice .Fetch(r=>r.FirstAssoc)
I'm sure I can avoid this but I cant figure out how. Any idea ?
Thanks !
If you select a specific 'MainEntity' then you can do it using QueryOver like so:
FirstAssoc firstAssoc = null;
Other other = null;
Another another = null;
tshead = session.QueryOver<MainEntity>()
.Where(x => x.Id == id)
.JoinAlias(x => x.FirstAssoc, () => firstAssoc)
.JoinAlias(() => firstAssoc.Other, () => other)
.JoinAlias(() => firstAssoc.Another, () => another)
.SingleOrDefault();
I've written about it here:
http://www.philliphaydon.com/2011/04/nhibernate-querying-relationships-are-depth/
You can't do:
One-Many-Many
only One-Many-One.
I'm not sure you can do Many-Many-One, transforming that would be too difficult.
could someone help me to translate LINQ expression to Nhibernate QueryOver
from m in messages
where !m.Recipients.Any(rcpt => rcpt.IsDeleted && rcpt.User = user)
I tried this
var qry = Session.QueryOver<UserMessage>();
qry.Where(m => m.Recipients.Any(r => !r.IsDeleted && r.User == user));
but got
System.Exception : Unrecognised method call: System.Linq.Enumerable:Boolean Any[TSource](System.Collections.Generic.IEnumerable1[TSource], System.Func2[TSource,System.Boolean]
!m.Recipients.Any(...) translates to a "not exists" sub-query. You will need a couple of aliases to correlate the sub-query with the main query, and the sub-query will need to have a projection to make NHibernate happy.
Try something like this:
UserMessage messageAlias = null;
UserMessage recipientMessageAlias = null;
var subquery = QueryOver.Of<MessageRecipient>()
.JoinAlias(x => x.Message, () => recipientMessageAlias)
.Where(x => x.IsDeleted == true) // your criteria
.Where(x => x.User.Id == userId)
.Where(() => recipientMessageAlias.Id == messageAlias.Id) // correlated subquery
.Select(x => x.Id); // projection
var query = session.QueryOver(() => messageAlias)
.Where(Subqueries.WhereNotExists(subquery));
return query.List();
I managed to it this way:
UserMessage messageAlias = null;
var qry = Session.QueryOver<UserMessage>(() => messageAlias);
UserMessageRecipient recipientAlias = null;
var deletedbyUser = QueryOver.Of(() => recipientAlias)
.Select(x => x.Id)
.Where( () => recipientAlias.Message.Id == messageAlias.Id
&& (recipientAlias.Recipient == query.User && recipientAlias.IsDeleted))
.DetachedCriteria;
qry.Where(Subqueries.NotExists(deletedbyUser));
Try to use the Linq version with session.Query<> instead of QueryOver
var qry = Session.Query<UserMessage>();
qry.Where(m => m.Recipients.Any(r => !r.IsDeleted && r.User == user));