I am trying to convert some old code to use Fluent Nhibernate.
Old code:
allOrders.OrderBy(x => x.OrdersLineItems.Count);
How do I convert it to something like:
query.AddOrder(new Order(????, true));
Is this even possible?
Thanks in advance
UPDATE:
Here is the simplified code I am trying to write:
ICriteria query = FluentSessionManager.GetSession().CreateCriteria<Orders>()
.AddOrder(new Order(????, true));
The joined table is OrdersLineItems. I need to set the order by the count of the line items. Since I am using paging with a data set that has over 500,000 records, simply pulling all the records into memory and then sorting them will not.
Thanks in advance.
ICriteria query = FluentSessionManager.GetSession().CreateCriteria<Orders>()
.CreateAlias("this.OrderLineItems", "oli")
.AddOrder(new Order(Projections.Count("oli.Id"), true));
Something like that I should think. It's probably not perfect but at least illustrates that you need to use Projections.Count to get it done.
Related
I want to count set of set of model in NHibernate using Criteria Query.
Account Model have Contacts(set) and Contact Model have Addresses(set).
I want to count addresses by giving input Account object.
I have implemented temporary by simple foreach loop.
If anyone know then please help me.
Thanks in advanced.
Thanks Radim Köhler,
I found my solution by :
var count = (Int32)Session.CreateCriteria(typeof(Account))
.Add(Restrictions.Eq("Id", account.Id))
.CreateCriteria("Contacts", "Contacts", JoinType.InnerJoin, Restrictions.IsNotEmpty("Addresses"))
.SetProjection(Projections.Count("Id")).UniqueResult(); .
Then I have used following criteria query:
var count = (Int32)Session.CreateCriteria(typeof(Address))
.CreateCriteria("Contact", "Contact",JoinType.InnerJoin)
.Add(Restrictions.Eq("Account.Id",accountId))
.SetProjection(Projections.Count("Id")).UniqueResult();
This give me actual result that I want by optimal query.
I am querying a MS SQL database using Linq and Entity Framework Code First. The requirement is to be able to run a WHERE SomeColumn LIKE '%sometext'clause against the table.
This, on the surface, is a simple requirement that could be accomplished using a simple Linq query like this:
var results = new List<MyTable>();
using(var context = new MyContext())
{
results = context.MyTableQueryable
.Where(x => x.SomeColumn.EndsWith("sometext"))
.ToList();
}
// use results
However, this was not effective in practice. The problem seems to be that the column SomeColumn is not varchar, rather it's a char(31). This means that if a string is saved in the column that is less than 31 characters then there will be spaces added on the end of the string to ensure a length of 31 characters, and that fouls up the .EndsWith() query.
I used SQL Profiler to lookup the exact sql that was generated from the .EndsWith() method. Here is what I found:
--previous query code removed for brevity
WHERE [Extent1].[SomeColumn] LIKE N'%sometext'
So that is interesting. I'm not sure what the N means before '%sometext'. (I'll Google it later.) But I do know that if I take the same query and run it in SSMS without the N like this:
--previous query code removed for brevity
WHERE [Extent1].[SomeColumn] LIKE '%sometext'
Then the query works fine. Is there a way to get Linq and Entity Framework to drop that N from the query?
Please try this...
.Where(x => x.SomeColumn.Trim().EndsWith("sometext"))
Just spoke to my colleague who had a similar issue, see if the following works for you:
[Column(TypeName = "varchar")]
public string SomeColumn
{
get;
set;
}
Apparently setting the type on the column mapping will force the query to recognise it as a VARCHAR, where a string is normally interpreted as an NVARCHAR.
I want to use Second level Cache for my query with eager loading(query is below wrote in 3 different ways, i use query cache). I have standard one to many association. I set entity cache for parent, child, and association between parent and class. And the 2nd level cache doesn't work because i got exceptions.
I wrote my query in 3 different way:
Criteria:
session.CreateCriteria<DictionaryMaster>().SetFetchMode("DictionaryItems", FetchMode.Eager)
.SetResultTransformer(new DistinctRootEntityResultTransformer())
.SetCacheable(true).SetCacheMode(CacheMode.Normal)
.List<DictionaryMaster>().ToList();
When I invoked this query i got exception "Unable to perform find[SQL: SQL not available]"
I think that the problem exists because I use DistinctRootEntityResultTransformer transform. I will start create my custom transform class and I hope that will work.
Query over:
session.QueryOver<DictionaryMaster>().Fetch(x => x.DictionaryItems).Eager
.TransformUsing(new DistinctRootEntityResultTransformer())
.Cacheable().CacheMode(CacheMode.Normal)
.List<DictionaryMaster>().ToList();
Exception is the same as in Criteria.
Linq:
session.Query<DictionaryMaster>().Fetch(x => x.DictionaryItems).Cacheable().CacheMode(CacheMode.Normal).ToList();
Here error depends from the version of nhibernate in 3.1 a got this error https://nhibernate.jira.com/browse/NH-2587?page=com.atlassian.jira.plugin.system.issuetabpanels%3Achangehistory-tabpanel
but in 3.2 version i got this: https://nhibernate.jira.com/browse/NH-2856
Thanks in advance
sJHony I have found solution, but for me is more like workaround. Therefore if you know any other solution give me sign.
I utilize QueryOver without any transformation, the fault of this solution is that the query return elements equal amount of childs. Next I retrieve not multiplied list in memory using distinct.
This solution is ok, but when we add one more Fetch for query, then collection in object also be multiplied, that is why i modified collection type from IList(Bag) to ISet(Set).
Code looks like:
var queryCacheResult =
session.QueryOver<DictionaryMaster>()
.Fetch(x => x.DictionaryItems).Eager
.Cacheable().CacheMode(CacheMode.Normal)
.List<DictionaryMaster>().ToList();
return queryCacheResult.Distinct(new KeyEqualityComparer<DictionaryMaster>(x => x.Code)).ToList();
In rails 3, I would like to do the following:
SomeModel.where(:some_connection_id => anArrayOfIds).select("some_other_connection_id")
This works, but i get the following from the DB:
[{"some_other_connection_id":254},{"some_other_connection_id":315}]
Now, those id-s are the ones I need, but I am uncapable of making a query that only gives me the ids. I do not want to have to itterate over the resulst, only to get those numbers out. Are there any way for me to do this with something like :
SomeModel.where(:some_connection_id => anArrayOfIds).select("some_other_connection_id").values()
Or something of that nautre?
I have been trying with the ".select_values()" found at Git-hub, but it only returns "some_other_connection_id".
I am not an expert in rails, so this info might be helpful also:
The "SomeModel" is a connecting table, for a many-to-many relation in one of my other models. So, accually what I am trying to do is to, from the array of IDs, get all the entries from the other side of the connection. Basicly I have the source ids, and i want to get the data from the models with all the target ids. If there is a magic way of getting these without me having to do all the sql myself (with some help from active record) it would be really nice!
Thanks :)
Try pluck method
SomeModel.where(:some => condition).pluck("some_field")
it works like
SomeModel.where(:some => condition).select("some_field").map(&:some_field)
SomeModel.where(:some_connection_id => anArrayOfIds).select("some_other_connection_id").map &:some_other_connection_id
This is essentially a shorthand for:
results = SomeModel.where(:some_connection_id => anArrayOfIds).select("some_other_connection_id")
results.map {|row| row.some_other_connection_id}
Look at Array#map for details on map method.
Beware that there is no lazy loading here, as it iterates over the results, but it shouldn't be a problem, unless you want to add more constructs to you query or retrieve some associated objects(which should not be the case as you haven't got the ids for loading the associated objects).
I am trying to retrieve data from a simple mySql table tbl_u_type which has just two columns, 'tid' and 'type'.
I want to use a direct SQL query instead of the Model logic. I used:
$command = Yii::app()->db->createCommand();
$userArray = $command->select('type')->from('tbl_u_type')->queryAll();
return $userArray;
But in the dropdown list it automatically shows an index number along with the required entry. Is there any way I can avoid the index number?
To make an array of data usable in a dropdown, use the CHtml::listData() method. If I understand the question right, this should get you going. Something like this:
$command = Yii::app()->db->createCommand();
$userArray = $command->select('tid, type')->from('tbl_u_type')->queryAll();
echo CHtml::dropdownlist('my_dropdown','',CHtml::listData($userArray,'tid','type'));
You can also do this with the Model if you have one set up for the tbl_u_type table:
$users = UType::model()->findall();
echo CHtml::dropdownlist('my_dropdown','',CHtml::listData($users ,'tid','type'));
I hope that gets you on the right track. I didn't test my code here, as usual, so watch out for that. ;) Good luck!