I'm having a heck of a time returning a few rows from my in-memory sqlite db that mocks an oracle db. I'm writing an NHibernate query to pull up rows by a nullable DateTime. I think I have it mapped correctly. Have a look:
The data object property:
public virtual System.Nullable<System.DateTime> RequiredInstallDt { get; set; }
The mapping:
Map(x => x.RequiredInstallDt).Column("REQUIRED_INSTALL_DT").Nullable();
There's two rows in the db. One that should be pulled up and one that shouldn't. The date I'm asking for is 2012-8-1. There's no time value and there isn't one in the db, which I've been able to verify. One row has Aug 1 and the other doesn't. I'm expecting one record returned.
If I say:
IList<Request> ra = new RequestDAO().ListAll();
which is a known working method in the same call as my query, I get the two records as expected.
I've tried several versions of the same query, using linq, hql, and the CreateCriteria versions. The result is almost always the same. I get 0 records back (the other way is a NHibernate.Hql.Ast.ANTLR.QuerySyntaxException so that's a PEBKAC). Here's one of those query versions:
DateTime installDate = new DateTime(2012, 8, 1);
var requests = session.CreateCriteria<Request>()
.Add(Restrictions.Ge("RequiredInstallDt", installDate))
.Add(Restrictions.Lt("RequiredInstallDt", installDate.AddDays(1)))
.List<Request>();
Thanks for reading.. I appreciate any input.
Try adding a not null restriction. Your query could be
DateTime installDate = new DateTime(2012, 8, 1);
var requests = session.CreateCriteria<Request>()
.Add(Restrictions.Ge("RequiredInstallDt", installDate))
.Add(Restrictions.Lt("RequiredInstallDt", installDate.AddDays(1)))
.Add(Restriction.IsNotNull("RequiredInstallDt"))
.List<Request>();
Related
Hello i'm trying to get all users which have had payments at least 6 months over the given period (which must be a year). I've written SQL which works fine, but i have difficulties trying to convert it to nhibernate.
SQL:
SELECT COUNT(UserId) AS paidMonthsCount, UserId FROM (
SELECT DISTINCT UserId,
YEAR(PayDate) as _year,
MONTH(PayDate) as _month
FROM Payments
WHERE PayDate >= '2014-04-02T00:00:00' AND PayDate < '2015-04-02T23:59:00'
)result GROUP BY result.UserId
i have converted inner SQL:
var subQuery = Session.QueryOver(() => paymentAlias)
.SelectList(list => list
.Select(Projections.Distinct(Projections.Property<VelferdPayment>(p => p.Client.Id)).WithAlias(() => userWithHelp.Id))
.Select(p => p.AssignmentYear).WithAlias(() => userWithHelp.AssignmentDate)
)
.WhereRestrictionOn(p => p.AssignmentDate)
.IsBetween(parameters.FromDate)
.And(parameters.ToDate);
which selects the distinct part and i have the other part which is selecting from result:
var query = Session.QueryOver(() => userWithHelp).
SelectList(list => list
.SelectCount(p=> p.Id).WithAlias(()=> userWithHelpCount.Count)
.SelectGroup(p => p.Id).WithAlias(() => userWithHelpCount.Id)
)
.TransformUsing(Transformers.AliasToBean<UserWithHelpCount>())
.List<UserWithHelpCount>();
How can i queryover the subQuery results or is it possible to write single request to SQL. Working for a long time please help.
In general, with NHibernate we can only (or mainly) query Entities, not TABLES. Other words, we firstly map tables or views or even some <subselect>s into entities. The below mapping of the User (C# object User)
<class name="user" table="[dbo].[user_table]" ...
Will allow us to create query over C# User.
session.QueryOver<User>()...
Behind the scene it will generate FROM clause, which will contain the content of table attribute, i.e. FROM [dbo].[user_table]
That's it. There is no other way how to set the generated FROM clause. Just by mapping.
But there is a way which allow us to use existing ADO.NET connection to create custom query and even convert its result to some entity, or DTO. It is CreateSQLQuery() API:
17.1.5. Returning non-managed entities
It is possible to apply an IResultTransformer to native sql queries. Allowing it to e.g. return non-managed entities.
sess.CreateSQLQuery("SELECT NAME, BIRTHDATE FROM CATS")
.SetResultTransformer(Transformers.AliasToBean(typeof(CatDTO)))
This query specified:
the SQL query string
a result transformer
The above query will return a list of CatDTO which has been instantiated and injected the values of NAME and BIRTHNAME into its corresponding properties or fields.
So, we can use native SQL SELECT statements to get any results. We can even create some custom DTO and let NHibernate to transform result into them...
Domain Model
I've got a canonical Domain of a Customer with many Orders, with each Order having many OrderItems:
Customer
public class Customer
{
public Customer()
{
Orders = new HashSet<Order>();
}
public virtual int Id {get;set;}
public virtual ICollection<Order> Orders {get;set;}
}
Order
public class Order
{
public Order()
{
Items = new HashSet<OrderItem>();
}
public virtual int Id {get;set;}
public virtual Customer Customer {get;set;}
}
OrderItems
public class OrderItem
{
public virtual int Id {get;set;}
public virtual Order Order {get;set;}
}
Problem
Whether mapped with FluentNHibernate or hbm files, I run two separate queries, that are identical in their Fetch() syntax, with the exception of one including the .First() extension method.
Returns expected results:
var customer = this.generator.Session.Query<Customer>()
.Where(c => c.CustomerID == id)
.FetchMany(c => c.Orders)
.ThenFetchMany(o => o.Items).ToList()[0];
Returns only a single item in each collection:
var customer = this.generator.Session.Query<Customer>()
.Where(c => c.CustomerID == id)
.FetchMany(c => c.Orders)
.ThenFetchMany(o => o.Items).First();
I think I understand what's going on here, which is that the .First() method is being applied to each of the preceding statements, rather than just to the initial .Where() clause. This seems incorrect behavior to me, given the fact that First() is returning a Customer.
Edit 2011-06-17
After further research and thinking, I believe that depending on my mapping, there are two outcomes to this Method Chain:
.Where(c => c.CustomerID == id)
.FetchMany(c => c.Orders)
.ThenFetchMany(o => o.Items);
NOTE: I don't think I can get subselect behavior, since I'm not using HQL.
When the mapping is fetch="join" I should get a cartesian product between the Customer, Order and OrderItem tables.
When the mapping is fetch="select" I should get a query for Customer, and then multiple queries each for Orders and OrderItems.
How this plays out with adding the First() method to the chain is where I lose track of what should be happening.
The SQL Query that get's issued is the traditional left-outer-join query, with select top (#p0) in front.
The First() method is translated into SQL (T-SQL at least) as SELECT TOP 1 .... Combined with your join fetching, this will return a single row, containing one customer, one order for that customer and one item for the order. You might consider this a bug in Linq2NHibernate, but as join fetching is rare (and I think you're actually hurting your performance pulling the same Customer and Order field values across the network as part of the row for each Item) I doubt the team will fix it.
What you want is a single Customer, then all Orders for that customer and all Items for all those Orders. That happens by letting NHibernate run SQL that will pull one full Customer record (which will be a row for each Order Line) and construct the Customer object graph. Turning the Enumerable into a List and then getting the first element works, but the following will be slightly faster:
var customer = this.generator.Session.Query<Customer>()
.Where(c => c.CustomerID == id)
.FetchMany(c => c.Orders)
.ThenFetchMany(o => o.Items)
.AsEnumerable().First();
the AsEnumerable() function forces evaluation of the IQueryable created by Query and modified with the other methods, spitting out an in-memory Enumerable, without slurping it into a concrete List (NHibernate can, if it wishes, simply pull enough info out of the DataReader to create one full top-level instance). Now, the First() method is no longer applied to the IQueryable to be translated to SQL, but it is instead applied to an in-memory Enumerable of the object graphs, which after NHibernate has done its thing, and given your Where clause, should be zero or one Customer record with a hydrated Orders collection.
Like I said, I think you're hurting yourself using join fetching. Each row contains the data for the Customer and the data for the Order, joined to each distinct Line. That is a LOT of redundant data, which I think will cost you more than even an N+1 query strategy.
The best way I can think of to handle this is one query per object to retrieve that object's children. It would look like this:
var session = this.generator.Session;
var customer = session.Query<Customer>()
.Where(c => c.CustomerID == id).First();
customer.Orders = session.Query<Order>().Where(o=>o.CustomerID = id).ToList();
foreach(var order in customer.Orders)
order.Items = session.Query<Item>().Where(i=>i.OrderID = order.OrderID).ToList();
This requires a query for each Order, plus two at the Customer level, and will return no duplicate data. This will perform far better than a single query returning a row containing every field of the Customer and Order along with each Item, and also better than sending a query per Item plus a query per Order plus a query for the Customer.
I'd like to update the answer with my found so that could help anybody else with the same problem.
Since you are querying the entity base on their ID, you can use .Single instead of .First or .AsEnumerable().First():
var customer = this.generator.Session.Query<Customer>()
.Where(c => c.CustomerID == id)
.FetchMany(c => c.Orders)
.ThenFetchMany(o => o.Items).Single();
This will generate a normal SQL query with where clause and without the TOP 1.
In other situation, if the result has more than one Customer, exception will be thrown so it won't help if you really need the first item of a series based on condition. You have to use 2 queries, one for the first Customer and let the lazy load do the second one.
I have a PrivateMessage class and I want to get list of PMs for user sorted chronologically either by CreationDate or LastAnswerDate (depending on which is more recent) using Criteria API.
How to sort by max of these two properies in Criteria API? My code looks similar to following:
var dc = DetachedCriteria.For<PrivateMessage>();
...
dc.AddOrder(new Order("???");
return (IList<PrivateMessage>)FindAll(typeof(PrivateMessage), dc);
CreationDate is DateTime and LastAnswerDate is DateTime?.
Thanks!
Order.Desc(
Projections.Conditional(
Restrictions.GtProperty("CreationDate", "LastAnswerDate"),
Projections.Property("CreationDate"),
Projections.Property("LastAnswerDate"))))
I have a simple test object model in which there are schools, and a school has a collection of students.
I would like to retrieve a school and all its students who are above a certain age.
I carry out the following query, which obtains a given school and the children which are above a certain age:
public School GetSchoolAndStudentsWithDOBAbove(int schoolid, DateTime dob)
{
var school = this.Session.CreateCriteria(typeof(School))
.CreateAlias("Students", "students")
.Add(Expression.And(Expression.Eq("SchoolId", schoolid), Expression.Gt("students.DOB", dob)))
.UniqueResult<School>();
return school;
}
This all works fine and I can see the query going to the database and returning the expected number of rows.
However, when I carry out either of the following, it gives me the total number of students in the given school (regardless of the preceding request) by running another query:
foreach (Student st in s.Students)
{
Console.WriteLine(st.FirstName);
}
Assert.AreEqual(s.Students.Count, 3);
Can anyone explain why?
You made your query on the School class and you restricted your results on it, not on the mapped related objects.
Now there are many ways to do this.
You can make a static filter as IanL said, however its not really flexible.
You can just iterate the collection like mxmissile but that is ugly and slow (especially considering lazy loading considerations)
I would provide 2 different solutions:
In the first you maintain the query you have and you fire a dynamic filter on the collection (maintaining a lazy-loaded collection) and doing a round-trip to the database:
var school = GetSchoolAndStudentsWithDOBAbove(5, dob);
IQuery qDob = nhSession.CreateFilter(school.Students, "where DOB > :dob").SetDateTime("dob", dob);
IList<Student> dobedSchoolStudents = qDob.List<Student>();
In the second solution just fetch both the school and the students in one shot:
object result = nhSession.CreateQuery(
"select ss, st from School ss, Student st
where ss.Id = st.School.Id and ss.Id = :schId and st.DOB > :dob")
.SetInt32("schId", 5).SetDateTime("dob", dob).List();
ss is a School object and st is a Student collection.
And this can definitely be done using the criteria query you use now (using Projections)
Unfortunately s.Students will not contain your "queried" results. You will have to create a separate query for Students to reach your goal.
foreach(var st in s.Students.Where(x => x.DOB > dob))
Console.WriteLine(st.FirstName);
Warning: That will still make second trip to the db depending on your mapping, and it will still retrieve all students.
I'm not sure but you could possibly use Projections to do all this in one query, but I am by no means an expert on that.
You do have the option of filtering data. If it there is a single instance of the query mxmissle option would be the better choice.
Nhibernate Filter Documentation
Filters do have there uses, but depending on the version you are using there can be issues where filtered collections are not cached correctly.
I have a nHibernate query like this
ICriteria query = session.CreateCriteria(typeof(MyResult))
.Add(Expression.Eq("ResultTypeId", myResult.ResultTypeId))
Problem is that users add results all the time and I want to show a table of all the latest results for all the diferent ResultTypes I have.
The MyResult class has a property ResultDate. My question is, what do I add to the query to get it to only return the latest result for the given result type. There is nothing to say that the results will be in date order in the database.
Thanks,
Mark
You can order the result by ResultDate using the AddOrder method, as below:
ICriteria query = session.CreateCriteria(typeof(MyResult))
.Add(Expression.Eq("ResultTypeId", myResult.ResultTypeId))
.AddOrder(Order.Desc("ResultDate"))
.List<MyResult>();
If you want to limit the number of MyResult instances you get back, you can use the SetMaxResults method, like so:
ICriteria query = session.CreateCriteria(typeof(MyResult))
.Add(Expression.Eq("ResultTypeId", myResult.ResultTypeId))
.AddOrder(Order.Desc("ResultDate"))
.SetMaxResults(20)
.List<MyResult>();
If I understand the question well, Mark wants to see an overview of all the last results for each type.
Which means that, for every result type, he only wants to see only one row, and that is the Result which has last been added for that type.
I think that, the easiest way to achieve this, would be to create an additional class, which we can call 'MyResultOverview' for instance:
public class MyResultOverview
{
public int ResultId {get; set;}
public int ResultTypeId {get; set;}
public DateTime ResultDate {get; set;}
}
This class should not be mapped, but NHibernate should be aware that this class exists. Therefore, we'll have to import it:
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" >
<import class="MyResultOverview" />
</hibernate-mapping>
Then, we can create an ICriteria which will populate instances of MyResultOverview (and which will also generate the most efficient SQL Query in order to get this overview).
It should look something like this:
ICriteria criteria = session.CreateCritera (typeof(MyResult));
criteria.SetProjection (Projections.ProjectionList ()
.Add (Projections.Property("Id"), "ResultId")
.Add (Projections.Property("ResultType"), "ResultType")
.Add (Projections.Max("ResultDate"), "ResultDate"));
criteria.SetResultTransformer (Transformers.AliasToBean (typeof(MyResultOverview)));
IList<MyResultOverview> results = criteria.List<MyResultOverview>();
This should give you a list of MyResultOverview instances which represent the MyResults that you're looking for.
Then, in order to retrieve the MyResult itself, you can simply do this by retrieving the MyResult instance for that particalur ResultId that you've retrieved as well.
I haven't tested this, nor did i compile it, but this is the path that I would follow to achieve this.
Order by ResultDate (descending) and select top whatever you feel appropriate.
In HQLthis might work:
select item, tag
from MyItem item
join item.Tags tag
where tag.Id = (
select max(tag2.Id)
from MyItem item2
join item2.Tags tag2
where item2.Id = item.Id
group by item2.Id
)