IDataServicePagingProvider.SetContinuationToken

Question

The documentation in V1.5 CTP2 describes the signature as

IQueryable SetContinuationToken (
 IQueryable query,
 ResourceType resourceType,
 Object[] continuationToken
)

However, its declaration in the assembly is actually 

void SetContinuationToken (
 IQueryable query,
 ResourceType resourceType,
 Object[] continuationToken
)

Which one is correct? Also, any insight into how to go about implementing the interface?


...Sorry, posted in the wrong forum.

Answer 1

In CTP2 documentation, it describes the IDataServicePagingProvider.SetContinuationToken call signature as

IQueryable SetContinuationToken (
 IQueryable query,
 ResourceType resourceType,
 Object[] continuationToken
)

However in the assembly it is declared as  

void SetContinuationToken (
 IQueryable query,
 ResourceType resourceType,
 Object[] continuationToken
)

Which is correct?

I implemented the PagingProvider and the DS runtime is calling SetContinuationToken with the proper arguments as such. However, I can't properly control the result set that is being returned to the client.

Frank


More information..

DS runtime calls RequestQueryProcessor.ProcessSkipToken to handling paging. Following is from .NET Reflector

      if (this.IsCustomPaged)
        {
            this.ApplyCustomPaging(queryStringItem);
        }
        else
        {
            this.ApplyStandardPaging(queryStringItem);
        }

RequestQueryProcessor.ApplyStandardPaging which in turns calls  RequestUriProcessor.InvokeWhereForType to further filters the query into the desired result set.

       this.query = RequestUriProcessor.InvokeWhereForType(this.query, this.orderingParser.BuildSkipTokenFilter(this.topLevelOrderingInfo, instance));

However, in RequestQueryProcessor.ApplyCustomPaging the call to SetContinucationToken is as follows

       this.service.PagingProvider.PagingProviderInterface.SetContinuationToken(this.query, this.description.LastSegmentInfo.TargetResourceType, continuationToken);

I just don't see how I can properly filter the result set.

Answer 2

Hi fcschow,

  The  documentation is incorrect for this interface., I will follow up internally.
 
  In the meantime , this interface is supposed to help one setup a custom paging provider for their  Data Service.
  Do you need to customize the default paging behavior ?
  If yes , some details of the behavior you are trying to achieve would be helpful in answering your question meaningfully.

---

Phani Raj Astoria http://blogs.msdn.com/PhaniRaj

Answer 3

Hi Phani,

Thanks for your reply.

I am one of those whom brought into the original SSDS ACE model (because we have a EAV-based application) and now have to do our own implementation.

For now, I am merely trying to replicate the DS default behavior using the custom provider interfaces so as to gain insight into our own implementation.

First, I implemented the IDataServiceQueryProvider over CLR objects. Most behavior work as expected including "Open Type".

I run into a dead-end with IDataServicePagingProvider. I use DataServiceConfiguration.SetEntitySetPageSize to alter the size, and when the DS runtime calls IDataServicePagingProvider.SetContinuationToken there is nothing I do to alter to the result set. As a result, I always get back the entire result set. DS default paging does behavior correctly if i left out my custom implementation.

The IDataServicePagingProvider interface described in the document does make sense. It gives implementation the ablility to alter the result set. I believe IDataServiceProjectionProvider.ApplyProjection works the same way.

Thoughts.

fcschow