I've a little problem: I would insert a condition into my QueryOver that checks also the variable value. Something like this:
var qOver = QueryOver.Of<MyModel>(() => myMod)
.JoinAlias(() => myMod.SubMod, () => subMod, JoinType.LeftOuterJoin)
.Where(Restrictions.Or(
Restrictions.On(() => myMod.ID).IsIn(MyIDList)
, Restrictions.On(MyIDList == null))
In SQL sintax something like
WHERE #Variable = '' OR MyTable.MyField = #Variable
So, if I my variable is filled I'll filter on my field. If my variable is empty (or null) I'll select every record without filter any content.
How can I reach this result using QueryOver and Restrinctions?
Thank you!
If the variable is null or not set, dont add it to your query.
var qOver = QueryOver.Of<MyModel>(() => myMod)
.JoinAlias(() => myMod.SubMod, () => subMod, JoinType.LeftOuterJoin);
if( MyIDList != null )
qOver = qOver.Where(Restrictions.Or(Restrictions.On(() => myMod.ID).IsIn(MyIDList))
Related
I'm accustomed to GroupBy() being more of an art than a science, but maybe someone can help me with a very specific problem:
Given the following code
var results = session.Query<MyClass>()
.GroupBy(c => c.OtherPersistentObject)
.Select(group => new
{
key = group.Key,
count = group.Count()
})
.ToList();
The generated query comes out like this:
/* [expression] */select
otherclass_.ID as col_0_0_,
cast(count(*) as INT) as col_1_0_,
otherclass_.ID as id1_1_,
otherclass_.START_DATE as start2_1_,
otherclass_.END_DATE as end3_1_,
otherclass_.Zone as zone9_1_
from
mytable mytable0_
left outer join
otherclass otherclass_
on mytable0_.otherID=otherclass_.ID
group by
mytable0_.otherID
which gives me the SQL error "Column 'otherclass .ID' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause"
Is there a way to get the Select to do what I want?
TIA
It's a known NHibernate issue NH-3027.
As a workaround you can use last approach described in this answer (rewrite GroupBy part as sub-query). So your query can be rewritten to something like:
var results = session.Query<MyClass>()
.Where(c => c == session.Query<MyClass>().First(cs => cs.OtherPersistentObject == c.OtherPersistentObject))
.Select(x => new
{
key = x.OtherPersistentObject,
count = session.Query<MyClass>().Count(cs => cs.OtherPersistentObject == x.OtherPersistentObject)
}).ToList();
Try this:
var results = session
.Query<MyClass>()
.GroupBy(c => c.OtherPersistentObject)
.Select(group => new
{
key = group.Key.Id,
count = group.Count()
})
.ToList();
Here you can find the reason for the error.
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();
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...
The following nhibernate query is causing me issues because it returns the same row more that once as the child tables have more than one row that match the criteria supplied. What i would like to know is the most efficient/ best practice in nhibernate to do this same query but to only get each row in DataMappingBase once. Returning multiple of the same row is breaking my number of results returned as i try to limit it 25 but sometimes i get the same row 25 times.
MappedID id = null;
DataMappingBase mapBase = null;
NameDetails name = null;
dmbs = mappingSession.QueryOver<DataMappingBase>(() => mapBase)
.JoinAlias(() => mapBase.IDs, () => id).WhereRestrictionOn(() => id.SecondaryDataIDType).IsNull()
.JoinAlias(() => mapBase.Names, () => name).WhereRestrictionOn(() => name.Name).IsInsensitiveLike(request.Filter, MatchMode.Anywhere)
.Take(request.MaxResults)
.List();
i am currently looking at converting the query above to a detached query and removing the "take" clause and getting it to just return the ID of the matching rows and have it used in a sub-query selecting from "DataMappingBase" where the rows ID is in the ids returned by the sub-query but i am not sure if that is the best way or not.
I'm not sure, but you can do like this:
MappedID id = null;
DataMappingBase mapBase = null;
NameDetails name = null;
dmbs = mappingSession.QueryOver<DataMappingBase>(() => mapBase)
.JoinAlias(() => mapBase.IDs, () => id).WhereRestrictionOn(() => id.SecondaryDataIDType).IsNull()
.JoinAlias(() => mapBase.Names, () => name).WhereRestrictionOn(() => name.Name).IsInsensitiveLike(request.Filter, MatchMode.Anywhere)
.Take(request.MaxResults)
// add this
.TransformUsing(Transformers.DistinctRootEntity)
.List();
Basically I crossed the same problem of Linq provider in this linq-to-nhibernate-produces-unnecessary-joins
List<Competitions> dtoCompetitions;
dtoCompetitions = (from compset in session.Query<FWBCompetitionSet>()
where compset.HeadLine == true
&& compset.A.B.CurrentSeason == true
select (new Competitions
{
CompetitionSetID = compset.CompetitionSetID,
Name = compset.Name,
Description = compset.Description,
Area = compset.Area,
Type = compset.Type,
CurrentSeason = compset.A.B.CurrentSeason,
StartDate = compset.StartDate
}
)).ToList();
Which leads to duplicated join in its generated SQL
SELECT fwbcompeti0_.competitionsetid AS col_0_0_,
fwbcompeti0_.name AS col_1_0_,
fwbcompeti0_.DESCRIPTION AS col_2_0_,
fwbcompeti0_.area AS col_3_0_,
fwbcompeti0_.TYPE AS col_4_0_,
fwbseason3_.currentseason AS col_5_0_,
fwbcompeti0_.startdate AS col_6_0_
FROM fwbcompetitionset fwbcompeti0_
INNER JOIN A fwbcompeti1_
ON fwbcompeti0_.competitionseasonid = fwbcompeti1_.competitionseasonid
INNER JOIN A fwbcompeti2_
ON fwbcompeti0_.competitionseasonid = fwbcompeti2_.competitionseasonid
INNER JOIN B fwbseason3_
ON fwbcompeti2_.seasonid = fwbseason3_.seasonid
WHERE fwbcompeti0_.headline = #p0
AND fwbseason3_.currentseason = #p1
Notice these joins, which are totally duplicated and also affect my SQL Server's performence.
INNER JOIN A fwbcompeti1_
ON fwbcompeti0_.competitionseasonid = fwbcompeti1_.competitionseasonid
INNER JOIN A fwbcompeti2_
ON fwbcompeti0_.competitionseasonid = fwbcompeti2_.competitionseasonid
Update1
In the NHibernate 3.2, this LiNQ bug is still valid, and I could not find a simple and reasonable Linq solution.
So I used QueryOver + JoinAlias + TransformUsing finishing the job, workds perfect to me.
FWBCompetitionSet compset = null;
FWBCompetitionSeason compseason = null;
FWBSeason season = null;
IList<Competitions> dtoCompetitions;
dtoCompetitions = session.QueryOver<FWBCompetitionSet>(() => compset)
.JoinAlias(() => compset.FWBCompetitionSeason, () => compseason)
.JoinAlias(() => compseason.FWBSeason, () => season)
.Where(() => compset.HeadLine == true)
.And(() => season.CurrentSeason == true)
.SelectList(
list => list
.Select(c => c.CompetitionSetID).WithAlias(() => compset.CompetitionSetID)
.Select(c => c.Name).WithAlias(() => compset.Name)
.Select(c => c.Description).WithAlias(() => compset.Description)
.Select(c => c.Area).WithAlias(() => compset.Area)
.Select(c => c.Type).WithAlias(() => compset.Type)
.Select(c => season.CurrentSeason).WithAlias(() => season.CurrentSeason)
.Select(c => c.StartDate).WithAlias(() => compset.StartDate)
)
.TransformUsing(Transformers.AliasToBean<Competitions>())
.List<Competitions>();
Yet Another Edit:
I think I finally found out what's going on. It seems that the LINQ to NHibernate provider has trouble navigating associations from the target to the source table and generates a separate join each time it encounters such an association.
Since you don't provide your mapping, I used the mapping from linq-to-nhibernate-produces-unnecessary-joins. This model has a Document with one Job and many TranslationUnits. Each TranslationUnit has many Translation entities.
When you try to find a Translation based on a Job, you are traversing the associations in the reverse order and the LINQ provider generates multiple joins: one for Translation -> TranslationUnit and one for TranslationUnit to Document.
This query will generate redundant joins:
session.Query<TmTranslation>()
.Where(x => x.TranslationUnit.Document.Job == job)
.OrderBy(x => x.Id)
.ToList();
If you reverse the navigation order to Document -> TranslationUnit -> Translation, you get a query that doesn't produce any redundant joins:
var items=(from doc in session.Query<Document>()
from tu in doc.TranslationUnits
from translation in tu.Translations
where doc.Job ==job
orderby translation.Id
select translation).ToList();
Given this quirkiness, QueryOver seems like a better option.
Previous Edit:
I suspect the culprit is compset.A.B.CurrentSeason. The first joined table (fwbcompeti1_) returns A.B while the next two (fwbcompeti2_ and fwbseason3_) are used to return A.B. The LINQ to NHibernate provider doesn't seem to guess that A is not used anywhere else and fails to remove it from the generated statement.
Try to help the optimizer a little by replacing CurrentSeason = compset.A.B.CurrentSeason with CurrentSeason = true from the select, since your where statement returns only items with CurrentSeason == true.
EDIT: What I mean is to change the query like this:
List<Competitions> dtoCompetitions;
dtoCompetitions = (from compset in session.Query<FWBCompetitionSet>()
where compset.HeadLine == true
&& compset.A.B.CurrentSeason == true
select (new Competitions
{
CompetitionSetID = compset.CompetitionSetID,
Name = compset.Name,
Description = compset.Description,
Area = compset.Area,
Type = compset.Type,
CurrentSeason = true,
StartDate = compset.StartDate
}
)).ToList();
I simply replace the value compset.A.B.CurrentSeason with true