Almost all ORM can lazy load related properties (collections or instances) that means additional db calls and specifically in Nettiers filling an object with n-childs implies (n+1) database calls with the related performance penalty.
On this post, I want expose one alternative to populate an entire object graph in just one database call.
The concept it's very simple and consists on deserialize a string returned from the database that contains an xml with the representation of the entire object graph.
Example
"In one application that uses the AdventureWorks database you need to get the orders with their order details and the product referenced in the order detail for a selected customer."
1) First develop a simple method to take a look to the string that the deserializer is expecting.
Usage:
string sampleData = GetSampleData(676);
Method:
protected string GetSampleData(int customerId)2) Create an stored procedure that returns an xml with the representation of the entire object graph
{
SalesOrderHeaderService salesOrderHeaderService = new SalesOrderHeaderService();
Type[] childTypes = new Type[] { typeof(TList<SalesOrderDetail>), typeof(Product) };
TList<SalesOrderHeader> salesOrders = salesOrderHeaderService.DeepLoadByCustomerID(customerId, true, DeepLoadType.IncludeChildren, childTypes);
return EntityHelper.SerializeXml<SalesOrderHeader>(salesOrders);
}
CREATE PROCEDURE [dbo].[SalesOrdersGetWithDetailsAndProductsByCustomerId]
@customerId int,
@result ntext OUTPUT
AS
BEGIN
SET NOCOUNT ON;
SET @result=
'<?xml version="1.0" encoding="utf-16"?><ArrayOfSalesOrderHeader xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">'
+
(SELECT SalesOrderHeader.*,
'<SalesOrderDetailCollection>' +
(SELECT SalesOrderDetail.*,
(SELECT Product.*
FROM Production.Product Product
WHERE Product.ProductID = SalesOrderDetail.ProductID
FOR XML RAW ('ProductIDSource'), ELEMENTS)
FROM Sales.SalesOrderDetail SalesOrderDetail
WHERE SalesOrderDetail.SalesOrderID = SalesOrderHeader.SalesOrderID
FOR XML AUTO, ELEMENTS)
+ '</SalesOrderDetailCollection>'
FROM
Sales.SalesOrderHeader SalesOrderHeader
WHERE SalesOrderHeader.CustomerID = @customerId
FOR XML AUTO, ELEMENTS)
+
'</ArrayOfSalesOrderHeader>'
SELECT @result
END;
3) Call the SP and deserialize the result
Usage:
TList<SalesOrderHeader> customerSalesOrders = SalesOrdersGetWithDetailsAndProductsByCustomerId(676);
Method:Notes:
protected TList<SalesOrderHeader> SalesOrdersGetWithDetailsAndProductsByCustomerId(int customerId)
{
SqlCommand command = new SqlCommand("SalesOrdersGetWithDetailsAndProductsByCustomerId");
command.CommandType = CommandType.StoredProcedure;
SqlParameter param = new SqlParameter("@result", SqlDbType.VarChar);
param.Direction = ParameterDirection.Output;
param.Size = 10000;
command.Parameters.Add(param);
command.Parameters.Add(new SqlParameter("@customerId", customerId));
DataRepository.Provider.ExecuteNonQuery(command);
string resultParameter = command.Parameters[0].Value.ToString().Replace("<", "<").Replace(">", ">").Replace("&lt;", "<").Replace("&gt;", ">");
return EntityHelper.DeserializeListXml<SalesOrderHeader>(resultParameter);
}
- Remove XmlIgnore Attribute for the related entities that you want populate. You can identify them by the "Source" sufix (ProductIDSource in the example).
- Attributes serialization is case sensitive, if you has applied some style on the UsePascalCasing codesmith template property, your class fields names casing could be different that the db field definition. In this case use field aliasing in the stored procedure select clause.
- To deepload a collection put the subquery on the select fields and enclose with the collections delimiter ('SalesOrderDetailCollection' in the example).
