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.
Related
Please need some help converting this sql query to nhibernate
select a.ID, count(b.ID)
from appusers a
left join weeklytasks b on a.ID = b.TaskOwner and b.taskstatus = 1
group by a.ID
It's difficult to answer without knowing your entities, mappings, used technology(ICreteria API, QueryOver, Linq).
But I can suggest this solution using QueryOver:
AppUser ownerAlias = null;
WeeklyTask taskAlias = null;
var result = Session.QueryOver(() => taskAlias)
.JoinAlias(x => x.TaskOwner,
() => ownerAlias,
NHibernate.SqlCommand.JoinType.RightOuterJoin,
Restrictions.Where(() => taskAlias.Status == 1))
.SelectList(list => list
.SelectGroup(x => ownerAlias.Id)
.SelectCount(x => x.Id))
.List<object[]>();
or this:
var result = Session.QueryOver<WeeklyTask>()
.Where(x => x.Status == 1)
.Right.JoinQueryOver(x => x.TaskOwner)
.SelectList(list => list
.SelectGroup(x => x.TaskOwner.Id)
.SelectCount(x => x.Id))
.List<object[]>();
Please notice that in this approach your WeeklyTask entity must contains mapped reference to AppUser entity.
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();
I need to use QueryOver instead of Linq but am struggling to recreate the following query:
public IQueryable<AuctionItem> GetLiveAuctionItems(){
repository.Query<AuctionItem>().Where(IsInActiveAuction()
}
public static Expression<Func<AuctionItem, bool>> IsInActiveAuction()
{
var now = SystemTime.Now();
var expression = PredicateBuilder.True<AuctionItem>();
return expression.And
(x => x.Lots.Any(
z => z.Auction.StartTime < now && z.Auction.EndTime > now && !z.DateWithdrawn.HasValue
&& z.DateApproved.HasValue));
}
I realise this creates subqueries but when I try to create using queryover I get errors stating projections needed.
Any help is much appreciated.
A quick draft with a clear how to steps. The first part, the subquery could look like this:
QueryOver<Lot> subQuery =
QueryOver.Of<Lot>(() => lot)
// Lot WHERE
.WhereRestrictionOn(() => lot.DateWithdrawn).IsNull
.AndRestrictionOn(() => lot.DateApproved).IsNotNull
// Auction JOIN
.JoinQueryOver<Auction>(l => l.Auction, () => auction)
// Auction WHERE
.Where(() => auction.StartTime < now)
.Where(() => auction.EndTime > now)
// AuctionItem.ID SELECT == projection
.Select(Projections.Property(() => lot.AuctionItem.ID))
;
So, this will return the AuctionItem.ID, which does meet our seraching criteria. And we can use it like this:
AuctionItem auctionItem = null;
var query = session.QueryOver<AuctionItem>(() => auctionItem)
.WithSubquery
.WhereProperty(() => auctionItem.ID)
.In(subQuery)
...
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 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