This is my simple structure:
public class Post{
public function user(){
return $this->belongsTo(User::class);
}
}
This is how I query (the query has pagination):
$query = Post::query();
$query->with('user');
I want to sort by user.name.
Now, I know that I can go $query->with('user',function(){...order by here});
But I need a detached method that I can run later in the stack.
$query->user->orderBy('name');
$query->user()->orderBy('name');
This https://stackoverflow.com/a/38741988/936651 says that it is possible, but I get the error: Undefined property/method: Illuminate\Database\Eloquent\Builder::$user
Is there any way to sort by related table after using with statement?
Thanks
Your code doesn't work because when you do $query = Post::query(); it will return an instance of the Query Builder, so when you after do $query->user() it gives you an error because the Query Builder does not have the method user(), that method exists in your Post model.
I won't provide any code since you've mentioned you already know how to do the with() way..
Related
Is it possible to invoke a user-defined SQL function from the query interface in EF Core? For example, the generated SQL would look like
select * from X where dbo.fnCheckThis(X.a, X.B) = 1
In my case, this clause is in addition to other Query() method calls so FromSQL() is not an option.
I just managed this with help from this article (H/T #IvanStoev for his comment on the question).
In your DbContext class:
[DbFunction("my_user_function_name")]
public static bool SatisfiesMyUserFunction(int i)
{
throw new Exception(); // this code doesn't get executed; the call is passed through to the database function
}
Note that the function must be in the DbContext class, even though it is static.
Then create a database migration and define the user function in the script.
Usage:
var query = db.Foos.Where(f => MyDbContext.SatisfiesMyUserFunction(f.FieldValue));
I'm writing a driver for EF Core for Spanner - In basic level it works and I can write Read and Write Queries that get's translated to Spanner SQL , executed and return results etc..
Now I'm trying to add Support For Read Query with Secondary Index.
Ultimately I'm trying to generate this SQL Query:
SELECT * FROM PostTags#{ FORCE_INDEX = PostTagsByTagId } WHERE TagId = 1
From This Linq:
var postTag = ctx.PostTags.WithIndex("PostTagsByTagId").Where(x => x.TagId == 1).FirstOrDefault();
I've added extension method as follow:
public static class SpannerIndexSupport
{
public static IQueryable<TSource> WithIndex<TSource>(this IQueryable<TSource> query, string indexName)
{
var methodDefinition = typeof(SpannerIndexSupport).GetTypeInfo().GetMethods().Single(m => m.Name == "WithIndex");
var method = methodDefinition.MakeGenericMethod(typeof(TSource));
var args = new[] { query.Expression, Expression.Constant(indexName) };
var expression = Expression.Call(null, method, args);
return query.Provider.CreateQuery<TSource>(expression);
}
}
And tried to write IAsyncQueryProvider to support it but couldn't find a way to make it work.
Any ideas Anyone?
In the official Spanner EFCore library (https://github.com/GoogleCloudPlatform/google-cloud-dotnet/tree/master/apis/Google.Cloud.EntityFrameworkCore.Spanner/Google.Cloud.EntityFrameworkCore.Spanner), I would start by overriding VisitTable(TableExpression tableExpression) in SpannerQuerySqlGenerator:
https://github.com/GoogleCloudPlatform/google-cloud-dotnet/tree/master/apis/Google.Cloud.EntityFrameworkCore.Spanner/Google.Cloud.EntityFrameworkCore.Spanner/Query/Sql/Internal/SpannerQuerySqlGenerator.cs
This will allow you to get a proof of concept going because you can directly influence the generated SQL text there.
Once that works, then you will want to make it proper.
I suppose there might be a few ways to make this work. The simplest might be to have some custom no-op method marker in the Linq expression tree and then register an IMethodCallTranslator to convert it either to a custom spanner specific Expression (whose Accept calls into SqlGenerator to generate the proper Sql) or possibly creating a SqlTranslatingExpressionVisitor to switch out the table expression to a custom one that allows the FORCE_INDEX.
Sorry I couldn't help more.
This is now supported in the official Entity Framework provider for Google Cloud Spanner. You can add this by adding a tag to the query like this:
var singersOrderedByFullName = context.Singers
// This will add the following comment to the generated query:
// `-- Use hint: force_index FullName`
// This comment will be picked up by the interceptor and an index
// hint will be added to the query that is executed.
.TagWith("Use hint: force_index FullName")
.OrderBy(s => s.FullName)
.AsAsyncEnumerable();
A full example can be found here: https://github.com/googleapis/dotnet-spanner-entity-framework/blob/main/Google.Cloud.EntityFrameworkCore.Spanner.Samples/Snippets/QueryHintSample.cs
I'm trying to load employees using Entity Framework.
The method is supposed to return employee list.
It' s giving this error:
Cannot implicit convert....<Class names and methods>.... An Explicit conversion exists.
I think the problem is related to casting.
Please check below code.
public List<Employee> LoadEmployees()
{
try
{
EMployeeDB1Entities EE = new EMployeeDB1Entities();
var Employees = EE.Employees.Where(p => p.Name.StartsWith("T"));
return Employees;
}
catch
{
return null;
}
}
var Employees = EE.Employees.Where(p => p.Name.StartsWith("T")).ToList();
Update your code to:
return Employees.ToList();
Also do note that this is the ToList() method that actually triggers the database query.
EE.Employees.Where(....) doesn't query the database. The DB is queried when the result of the Where() is enumerated, which is what .ToList() does.
Thanks it works...one more issue, suppose if I want to bind above list
to grid then how can I bind ?
Assuming you're using WPF or Silverlight:
To bind the result of your query on a datagrid, you could expose a public property of type ObservableCollection.
This collection accepts an IEnumerable<T> object as constructor.
You can write:
var myCollection = new ObservableCollection<Employee>(this.LoadEmployees());
Then bind the ItemSource property of your datagrid to your collection.
If you have more problems using bindings, I recommend you to ask another question, because the subject is quite different.
I am using EF 4.0 and POCO's. I stumbled across this error while inserting to records into the data base.
Property accessor 'QualityReasonID' on object 'BI.Entities.QualityReason' threw the following exception:'Object does not match target type.'
There errors occur on the Databind to a GridView after saving a new record to the database. I identified what is happening but I am not sure WHY it is occurring or If I am using EF/POCO's incorrectly. Any insight would be appreciated.
The exception is occuring because the object types in the IEnumerable are not the same.
The orginal entrys in the table are of type System.Data.Entity.DynamicProxies.QualityReason_E483AD567288B459706092F1825F53B1F93C65C5329F8095DD1D848B5D039F04}
While the new one is BI.Entities.QuailtyReason.
Here is how I insert the new object.
public void createQualityReason(QualityReason qReasons)
{
dbcontext.QualityReasons.AddObject(qReasons);
dbcontext.SaveChanges();
}
I resolved the error by changing the fetch code from:
public IEnumerable<QualityReason> fetchQualityReasons()
{
IEnumerable<QualityReason> queryReasons = dbcontext.QualityReasons.AsEnumerable();
return queryReasons;
}
to
public IEnumerable<QualityReason> fetchQualityReasons()
{
IEnumerable<QualityReason> queryReasons = from data in dbcontext.QualityReasons.AsEnumerable()
select new QualityReason
{
QualityReasonID = data.QualityReasonID,
QualityReasonName = data.QualityReasonName
};
return queryReasons;
}
So to get around the error I have to select into the POCO class explicitly each time. This feels like I am going something wrong. Any thoughts?
The error is caused because GridView does not handle polymorphic datasources when using boundfields. So you have two options
Use TemplateFields instead which can handle polymorphic datasources, this may changing some of your front end code and GridView events.
Use Linq to create a non-polymorphic databsource that the boundfields can handle
So instead of using something like ti
gvGroups.DataSource = ProductHelper.Get()
gvGroups.DataBind();
var query = from p in ProductHelper.Get()
select new {p.ProductId, p.ProductName, p.ProductDesc, p.ProductLink};
gvGroups.DataSource = query;
gvGroups.DataBind();
I don't know if the problem has been solved yet, but I've had the same problem with my (POCO) "Scenario" class.
The problem disappeared when using a context.CreateObject<Scenario> to create the (POCO) object i.s.o. a .... = new Scenario().
Faced the same issue today and used Value Injecter to solve it. It's as simple as:
var dynamicProxyMember = _repository.FindOne<Member>(m=>m.Id = 1);
var member = new Member().InjectFrom(dynamicProxyMember) as Member;
That's it :)
I'm having problems querying the entity model to get additional information.
My db has a Program table with a one to many relation with an Events table. The Entity model generates the relationships just fine, but I'm unable to figure out how to query the model to get the progam object with its events.
I can do this:
var foo = from program in entities.ProgramSet
where program.StartDate > DateTime.now
orderby program.StartDate
select program;
No problems there. From what I've found on Microsofts Page (Shaping queries with Entity framework): msdn.microsoft.com/en-us/library/bb896272.aspx, if I wanted to get the child objects, I just do the following:
// Define a LINQ query with a path that returns
// orders and items for a contact.
var contacts = (from contact in context.Contact
.Include("SalesOrderHeader.SalesOrderDetail")
select contact).FirstOrDefault();
However, there is no .Include or Include that I can find on the query.
Any suggestion? I know that I can do a foreach across the results, then run a .Events.Load() on it, but doesn't that force the IQueriable result to execute the sql, instead of optomize it to run only when a .ToList() etc is called on it?
Here is some sample code from my project:
public class ProgramRepository : CT.Models.IProgramRepository
{
CTEntities db = new CTEntities();
public IQueryable<Program> FindAllPrograms()
{
return db.ProgramSet;
}
public IQueryable<Program> FindUpcomingPrograms()
{
var programs = from program in FindAllPrograms()
where program.StartDate > DateTime.Now
orderby program.StartDate
select program;
return programs;
}
With the FindUpComingPrograms I would like to have it also include the Events Data. There is a relationship between the Program and Events model. Program has a List<Events> property, that I would like to fill and return with the IQueryable method.
Thanks again!
The Include Function is part of the ObjectQuery object...
I think you are going to need to re-write your query to look something like this:
var contacts = context.Contact.Include("SalesOrderHeader.SalesOrderDetail").FirstOrDefault();
//Not sure on your dot path you might have to debug that a bit
Here is an Article that has some examples...