Finally tracked down my error which is a result of the query. I have an nhibernate query using a Restrictions.In. Problem is once query executes if no results returned query throws error immediately. Is there another restriction that I can use. I know if I was writing a linq query I could use the .Any to return bool value and go from there is there something similar I can do in this instance?
carMake is passed in
myQuery.JoinQueryOver(x => x.Car)
.Where(Restrictions.In("VIN",
Trades.Where(x => x.Car.Make.ToLower() == carMake.ToLower())
.Select(x => x.Car.PrimaryVIN)
.ToList()));
Assuming that Trades is a list of objects you can use .WhereRestrictionOn() instead. Try this (I split the code for better readability):
var vinsWithCarMake = Trades
.Where(x => x.Car.Make.ToLower() == carMake.ToLower())
.Select(x => x.Car.PrimaryVIN)
.ToList<string>();
var carAlias = null;
var result = myQuery.JoinAlias(x => x.Car, () => carAlias)
.WhereRestrictionOn(() => carAlias.VIN).IsInG<string>(vinsWithCarMake)
.List();
Related
I tried different ways to solve this but either it wont let me include or it gives error for the GroupBy statement.
In the above code, I am trying to Group the MedicineEquipments by FOREIGN KEY i.e LocationId, and take the latest record with that LocationId and also include Location and MedicineEquipmentNavigation along with the record.
var medicineEquipmentShops = await dbContext.MedicineEquipments
.Where(x => x.CityId == cityId && x.MedicineEquipmentId == medicineEquippmentId)
.Include(x => x.Location)
.Include(x =>x.MedicineEquipmentNavigation)
.ToListAsync();
medicineEquipmentShops = medicineEquipmentShops.GroupBy(x => x.LocationId)
.Select(x => x.OrderByDescending(y => y.UpdatedOn).FirstOrDefault())
.OrderByDescending(x => x.IsVerified)
.ThenByDescending(x => x.Stock)
.ThenByDescending(x => x.Votes)
.ToList();
How do I add optional where clauses with QueryOver?
TL;DR
I am trying to implement a search form for an application and use QueryOver.
Some of the search parameters are optional.
var query =
myDatabase.QueryOver(() => customerAlias)
.JoinAlias(() => customerAlias.Projects, () => projectAlias)
.Where(() => projectAlias.IsClosed >= 1)
... possibly add more stuff
QueryOver is deferred in execution as for usual Linq statements. It will only execute when you force it to by calling a finalising method such as .List<T>().
var query =
myDatabase.QueryOver(() => customerAlias)
.JoinAlias(() => customerAlias.Projects, () => projectAlias)
.Where(() => projectAlias.IsClosed >= 1);
if (myCondition) {
query = query.Where(...);
}
var result = query.List<T>(); //Or however else you want to make it execute.
You should still be able to access the in-line aliases too this way.
how can I do this with queryover and a subquery?
FakturaObjektGutschrift fog = null;
int[] idS = Session.QueryOver(() => fog)
.SelectList( list => list
.SelectMax(() => fog.Id)
.SelectGroup(() => fog.SammelKontierung)
).List<object[]>().Select(x => (int)x[0]).ToArray();
And using the ids in another query
IQueryOver<Beleg, Beleg> sdfsd = Session.QueryOver(() => bGut)
.AndRestrictionOn(() => fog.Id).IsIn(idS); //iDs is a list of int.
I would like do this with a subquery because there is a limitation on the number of parameters for a SQL query. How do I do this?
How do I write the first query, but without selecting the SelectGroup()? This is exactly where I got stuck.
Group by without projection in QueryOver API is currently not supported link.
You can use LINQ to create the projection in a subquery:
var subquery = Session.Query<FakturaObjektGutschrift>()
.GroupBy(x => x.SammelKontierung)
.Select(x => x.Max(y => y.Id));
var query = Session.Query<Beleg>()
.Where(x => subquery.Contains(x.Id));
If you really needs QueryOver to create more complex queries check this solution link.
I have a problem with translating this SQL into QueryOver notation. Can you help me?
SELECT * FROM Alerts a
WHERE a.CreatedOn = (
SELECT MAX(b.CreatedOn) FROM Alerts b WHERE b.UserFk=a.UserFk);
I try to select last alert for every user. I use CreatedOn and cannot use Id.
I have so far:
session.QueryOver(() => alertAlias)
.SelectList(list => list
.Select(() => alertAlias.User.Id)
.SelectSubQuery(
QueryOver.Of<Alerts>()
.Where(x => x.User.Id == alertAlias.User.Id)
.OrderBy(x => x.CreatedOn).Desc
.Select(x => x.CreatedOn)
.Take(1)));
I know it adds user's last alert date to every user's alert row. But I want to have only last alerts.
Your attempt is using subquery inside of a SELECT statement. But we need to move it into WHERE. This should be the way:
// this is a subquery (SELECT ....
var subquery = QueryOver.Of<Alerts>()
.Where(x => x.User.Id == alertAlias.User.Id)
.OrderBy(x => x.CreatedOn).Desc
.Select(x => x.CreatedOn)
.Take(1)));
// main Query could now have or do not have that subquery selected
var query = session.QueryOver(() => alertAlias)
.SelectList(list => list
.Select(() => alertAlias.User.Id)
// could be there
.SelectSubQuery(subquery)
)
// but mostly here we do use WHERE clause
.WithSubquery
.WhereProperty(() => alertAlias.CreatedOn)
.Eq(subquery)
;
// such a query could be returned as a list of arrays
var results = query.List<object[]>();
We can also use some Result Transformer, but this is another story...
There's sooo much literature about fetching and eager loading when doing the actual query using .Fetch
But, once I have a loaded entity - with an empty collection (because I chose not to eager load at query time due to the cartesian product side-effect), can I choose to load a collection a bit later on, say after I've done some paging and I have a concrete List of items?
something like:
var list = (some linq over Session.Query<Entity>)
.Take(10).Skip(2)
.Fetch(x => x.MyCollection)
.ToList();
Session.Fetch<Entity>(list, l => l.OtherCollection);
Edit
The point is - i'm already fetching 2 child collections in the Query - makes the query and result set quite sizeable already (see nhibernate Cartesian product). I'd like page the results, get a list of 10 then optionally go back to the database to populate child collection properties of the paged (10, say) result. This is a performance consideration.
Issue this query
/*we dont need the result*/Session.QueryOver<Entity>()
.Where(x => x.Id.IsIn(list.Select(l => l.Id)))
.Fetch(l => l.OtherCollection)
.ToList();
then nhibernate should initialize the collections on the Entities
EDIT:
to improve initial loading time see http://ayende.com/blog/4367/eagerly-loading-entity-associations-efficiently-with-nhibernate
then you can do for exmaple
var results = (some linq over Session.Query<Entity>)
.Take(10).Skip(2)
.ToList();
var q = Session.QueryOver<Entity>()
.Where(x => x.Id.IsIn(list.Select(l => l.Id)))
.Fetch(l => l.MyCollection)
.ToFuture();
Session.QueryOver<Entity>()
.Where(x => x.Id.IsIn(list.Select(l => l.Id)))
.Fetch(l => l.OtherCollection)
.ToFuture();
Session.QueryOver<Entity>()
.Where(x => x.Id.IsIn(list.Select(l => l.Id)))
.Fetch(l => l.ThirdCollection)
.ToFuture();
return q.ToList()
I've just gone off to read about futures and projections in NHibernate which look promising as a solution...will post more when I find out about it.
This is a solution: http://ayende.com/blog/4367/eagerly-loading-entity-associations-efficiently-with-nhibernate, but I still do not like it, as my query itself is quite expensive (uses '%like%# + paging), so executing 3 or 4 times just to load collections seems expensive
Edit
This is what I have. Lookign at the sql generated, the correct sql is being run and returning expected results, but the collections on the returned results are null. Can you see what's missing?:
public List<Company> CompaniesForLoggedInUser(int pageSize, int pageNumber)
{
var list =
QueryForCompaniesFor(SecurityHelper.LoggedInUsername)
.Page(pageNumber, pageSize)
.ToList()
.FetchCompanyCollections(Session);
return list;
}
internal static class CompanyListExtensions
{
internal static List<Company> FetchCompanyCollections(this List<Company> companies, ISession session)
{
var ids = companies.Select(l => l.Id).ToArray();
session.QueryOver<Company>()
.Where(x => x.Id.IsIn(ids))
.Fetch(l => l.Properties).Eager()
.Future();
return session.QueryOver<Company>()
.Where(x => x.Id.IsIn(ids))
.Fetch(l => l.UserAccessList).Eager()
.Future()
.ToList();
}
}