I'm looking for a way to map several POCO objects into single table in the ServiceStack.
Is it possible to do this in a clean way, without "hacking" table creation process?
As a general rule, In OrmLite: 1 Class = 1 Table.
But I'm not clear what you mean my "map several POCO objects into single table", it sounds like using Auto Mapping to populate a table with multiple POCO instances, e.g:
var row = db.SingleById<Table>(id);
row.PopulateWithNonDefaultValues(instance1);
row.PopulateWithNonDefaultValues(instance2);
db.Update(row);
If you need to maintain a single table and have other "sub" classes that maintain different table in the universal table you can use [Alias] so all Update/Select/Insert's reference the same table, e.g:
public class Poco
{
public int Id { get; set; }
public string Name { get; set; }
public int Age { get; set; }
}
[Alias(nameof(Poco))]
public class PocoName
{
public int Id { get; set; }
public string Name { get; set; }
}
[Alias(nameof(Poco))]
public class PocoAge
{
public int Id { get; set; }
public int Age { get; set; }
}
Although I don't really see the benefit over having a single table that you use AutoMapping to map your other classes to before using that in OrmLite.
Related
let's say I have
public class EFObject
{
public int Id { get; set; }
public int NavId { get; set; }
public NavObject Nav { get; set; }
}
public class DTOObject
{
public int Id { get; set; }
public int NavId { get; set; }
public string NavName { get; set; }
}
My expectation was high, and I thought to my self the built-in flattening should handle this, so my mapping is very simple
CreateMap<DTOObject, EFObject>().ReverseMap();
Unfortunately, converting DTOObject to EFObject does not work as expected because EFObject.Nav is null. Since I used the name NavId and NavName I would expect it to create a new NavObject and set the Nav.Id and Nav.Name accordingly.
My Problem : Is there a feature in Automapper that will allow me to achieve the intended result without having to manually write a rule to create an NavObject when mapping the Nav property?.
Unflattening is only configured for ReverseMap. If you want unflattening, you must configure Entity -> Dto then call ReverseMap to create an unflattening type map configuration from the Dto -> Entity.
as noted by Automapper documentation here
Well, in ServiceStack
where can I read up on the merits and differences of
[References(typeof(ABC))] and
[ForeignKey(typeof(XYZ) ]
What are they used for ? (I know, rather naively put but I have a hard time finding the basic description)
The docs for both are referenced throughout ServiceStack.OrmLite project page.
Use either for simple Foreign Keys
Essentially they're both equivalent to define simple Foreign Keys which you can use either for:
[References(typeof(ForeignKeyTable1))]
public int SimpleForeignKey { get; set; }
[ForeignKey(typeof(ForeignKeyTable1))]
public int SimpleForeignKey { get; set; }
The [References] attribute is also used by other data persistence libraries like PocoDynamo for DynamoDb where it would be preferred when wanting to re-use your existing data models else where, it's also useful as a benign "marker" attribute on different models when you want to include a navigable reference to an associated type for the property.
Fine-grained Foreign Key options
The [ForeignKey] is specific to OrmLite and includes additional fine-grained options for defining foreign key relationships specific to RDBMS's like different cascading options, e.g:
public class TableWithAllCascadeOptions
{
[AutoIncrement] public int Id { get; set; }
[ForeignKey(typeof(ForeignKeyTable1))]
public int SimpleForeignKey { get; set; }
[ForeignKey(typeof(ForeignKeyTable2), OnDelete = "CASCADE", OnUpdate = "CASCADE")]
public int? CascadeOnUpdateOrDelete { get; set; }
[ForeignKey(typeof(ForeignKeyTable3), OnDelete = "NO ACTION")]
public int? NoActionOnCascade { get; set; }
[Default(typeof(int), "17")]
[ForeignKey(typeof(ForeignKeyTable4), OnDelete = "SET DEFAULT")]
public int SetToDefaultValueOnDelete { get; set; }
[ForeignKey(typeof(ForeignKeyTable5), OnDelete = "SET NULL")]
public int? SetToNullOnDelete { get; set; }
}
We have a DTO - Employee - with many (> 20) related DTOs and DTO collections. For "size of returned JSON" reasons, we have marked those relationships as [Ignore]. It is then up to the client to populate any related DTOs that they would like using other REST calls.
We have tried a couple of things to satisfy clients' desire to have some related Employee info but not all:
We created a new DTO - EmployeeLite - which has the most-requested fields defined with "RelatedTableNameRelatedFieldName" approach and used the QueryBase overload and that has worked well.
We've also tried adding a property to a request DTO - "References" - which is a comma-separated list of related DTOs that the client would like populated. We then iterate the response and populate each Employee with the related DTO or List. The concern there is performance when iterating a large List.
We're wondering if there a suggested approach to what we're trying to do?
Thanks for any suggestions you may have.
UPDATE:
Here is a portion of our request DTO:
[Route("/employees", "GET")]
public class FindEmployeesRequest : QueryDb<Employee> {
public int? ID { get; set; }
public int[] IDs { get; set; }
public string UserID { get; set; }
public string LastNameStartsWith { get; set; }
public DateTime[] DateOfBirthBetween { get; set; }
public DateTime[] HireDateBetween { get; set; }
public bool? IsActive { get; set; }
}
There is no code for the service (automagical with QueryDb), so I added some to try the "merge" approach:
public object Get(FindEmployeesRequest request) {
var query = AutoQuery.CreateQuery(request, Request.GetRequestParams());
QueryResponse<Employee> response = AutoQuery.Execute(request, query);
if (response.Total > 0) {
List<Clerkship> clerkships = Db.Select<Clerkship>();
response.Results.Merge(clerkships);
}
return response;
}
This fails with Could not find Child Reference for 'Clerkship' on Parent 'Employee'
because in Employee we have:
[Ignore]
public List<Clerkship> Clerkships { get; set; }
which we did because we don't want "Clerkships" with every request. If I change [Ignore] to [Reference] I don't need the code above in the service - the List comes automatically. So it seems that .Merge only works with [Reference] which we don't want to do.
I'm not sure how I would use the "Custom Load References" approach in an AutoQuery service. And, AFAIKT, the "Custom Fields" approach can't be use for related DTOs, only for fields in the base table.
UPDATE 2:
The LoadSelect with include[] is working well for us. We are now trying to cover the case where ?fields= is used in the query string but the client does not request the ID field of the related DTO:
public partial class Employee {
[PrimaryKey]
[AutoIncrement]
public int ID { get; set; }
.
.
.
[References(typeof(Department))]
public int DepartmentID { get; set; }
.
.
.
public class Department {
[PrimaryKey]
public int ID { get; set; }
public string Name { get; set; }
.
.
.
}
So, for the request
/employees?fields=id,departmentid
we will get the Department in the response. But for the request
/employees?fields=id
we won't get the Department in the response.
We're trying to "quietly fix" this for the requester by modifying the query.SelectExpression and adding , "Employee"."DepartmentID" to the SELECT before doing the Db.LoadSelect. Debugging shows that query.SelectExpression is being modified, but according to SQL Profiler, "Employee"."DepartmentID" is not being selected.
Is there something else we should be doing to get "Employee"."DepartmentID" added to the SELECT?
Thanks.
UPDATE 3:
The Employee table has three 1:1 relationships - EmployeeType, Department and Title:
public partial class Employee {
[PrimaryKey]
[AutoIncrement]
public int ID { get; set; }
[References(typeof(EmployeeType))]
public int EmployeeTypeID { get; set; }
[References(typeof(Department))]
public int DepartmentID { get; set; }
[References(typeof(Title))]
public int TitleID { get; set; }
.
.
.
}
public class EmployeeType {
[PrimaryKey]
public int ID { get; set; }
public string Name { get; set; }
}
public class Department {
[PrimaryKey]
public int ID { get; set; }
public string Name { get; set; }
[Reference]
public List<Title> Titles { get; set; }
}
public class Title {
[PrimaryKey]
public int ID { get; set; }
[References(typeof(Department))]
public int DepartmentID { get; set; }
public string Name { get; set; }
}
The latest update to 4.0.55 allows this:
/employees?fields=employeetype,department,title
I get back all the Employee table fields plus the three related DTOs - with one strange thing - the Employee's ID field is populated with the Employee's TitleID values (I think we saw this before?).
This request fixes that anomaly:
/employees?fields=id,employeetypeid,employeetype,departmentid,department,titleid,title
but I lose all of the other Employee fields.
This sounds like a "have your cake and eat it too" request, but is there a way that I can get all of the Employee fields and selective related DTOs? Something like:
/employees?fields=*,employeetype,department,title
AutoQuery Customizable Fields
Not sure if this is Relevant but AutoQuery has built-in support for Customizing which fields to return with the ?fields=Field1,Field2 option.
Merge disconnected POCO Results
As you've not provided any source code it's not clear what you're trying to achieve or where the inefficiency with the existing solution lies, but you don't want to be doing any N+1 SELECT queries. If you are, have a look at how you can merge disconnected POCO results together which will let you merge results from separate queries based on the relationships defined using OrmLite references, e.g the example below uses 2 distinct queries to join Customers with their orders:
//Select Customers who've had orders with Quantities of 10 or more
List<Customer> customers = db.Select<Customer>(q =>
q.Join<Order>()
.Where<Order>(o => o.Qty >= 10)
.SelectDistinct());
//Select Orders with Quantities of 10 or more
List<Order> orders = db.Select<Order>(o => o.Qty >= 10);
customers.Merge(orders); // Merge disconnected Orders with their related Customers
Custom Load References
You can selectively control which references OrmLite should load by specifying them when you call OrmLite's Load* API's, e.g:
var customerWithAddress = db.LoadSingleById<Customer>(customer.Id,
include: new[] { "PrimaryAddress" });
Using Custom Load References in AutoQuery
You can customize an AutoQuery Request to not return any references by using Db.Select instead of Db.LoadSelect in your custom AutoQuery implementation, e.g:
public object Get(FindEmployeesRequest request)
{
var q = AutoQuery.CreateQuery(request, Request);
var response = new QueryResponse<Employee>
{
Offset = q.Offset.GetValueOrDefault(0),
Results = Db.Select(q),
Total = (int)Db.Count(q),
};
return response;
}
Likewise if you only want to selectively load 1 or more references you can change LoadSelect to pass in an include: array with only the reference fields you want included, e.g:
public object Get(FindEmployeesRequest request)
{
var q = AutoQuery.CreateQuery(request, Request);
var response = new QueryResponse<Employee>
{
Offset = q.Offset.GetValueOrDefault(0),
Results = Db.LoadSelect(q, include:new []{ "Clerkships" }),
Total = (int)Db.Count(q),
};
return response;
}
I have a data model that has a folder structure defined through the data. Various objects can be in these folders, including folders themselves, similarly to how folders in Explorer cascade and can contain each other.
I think I've figured out how foreign keys work in this stack, but when I go to migrate it to the database, the system won't let me. What's the issue? There's got to be a way to nest these folder entries inside each other, right?
namespace api.Models
{
public class Folder
{
public int Id { get; set; }
[Required]
public string Name { get; set; }
public int SuperFolderId { get; set; }
public Folder SuperFolder { get; set; }
}
}
The oversight here is that self-referencing foreign keys can't be nullable. Imagine a file structure where EVERY folder needs a superfolder. It would either go up forever, or two folders would have to reference each other and it would loop.
It's the same as the classic self-referencing key example of Employees having Managers, where Managers are also on the Employee table. You can only go so far up the chain before you reach the head of the company.
The system assumes foreign keys are not nullable, and so it makes them required without the need of the [Required] attribute. It is sometimes valid to make a foreign key optional, and to do that, you turn the int into a nullable int, or "int?". The code below fixes the problem.
namespace api.Models
{
public class Folder
{
public int Id { get; set; }
[Required]
public string Name { get; set; }
public int? SuperFolderId { get; set; }
public Folder SuperFolder { get; set; }
}
}
I don't know how to store collection (Comments) in separate table.
By default comments are serialized and stored in SomeClass table as column Comments.
[{Id:0,CreateDate:2013-09-12T14:28:37.0456202+02:00,,SomeClassID:1,CommentText:"coment text",}]
Is there any way to save it in separate tables?
public class SomeClass {
[AutoIncrement]
public int Id { get; set; }
public string Title { get; set; }
List<Comment> comments = new List<Comment>();
public List<Comment> Comments {
get { return comments; }
set { comments = value; }
}
}
public class Comment {
[AutoIncrement]
public int Id { get; set; }
[References(typeof(SomeClass))]
public int SomeClassID { get; set; }
[StringLength(4000)]
public string CommentText { get; set; }
}
I don't think ORMLite supports serializing to multiple tables. 1 table = 1 class so the comments will be stored as a Blob field in the SomeClass table.
If you need to store them in separate tables you will have to save the comments separately and have a foreign key reference back to the id of the SomeClass table.