Cosmos IQueryable throws "LINQ query please set allowSynchronousQueryExecution true or use GetItemQueryIterator to execute asynchronously"

[onionhammer]

Is there an existing issue for this?

• I have searched the existing issues

Product

Hot Chocolate

Describe the bug

When returning a Cosmos Linq Queryable, HotChocolate throws because it appears to be attempting to access the IQueryable synchronously (rather than async)

[UseFiltering]
public IQueryable<MyModel> GetPartner() =>
    MyContainer.GetItemLinqQueryable<MyModel>();

Steps to reproduce

1. Connect your program to a cosmos database
2. Return a queryable ala MyContainer.GetItemLinqQueryable()
3. Exception happens when accessing that node

Relevant log output

GraphQL service exception for 'POST /graphql/UnknownOperation - 662a00b5500da5b6c5c6a01ee7142acd': To execute LINQ query please set allowSynchronousQueryExecution true or use GetItemQueryIterator to execute asynchronously
      System.NotSupportedException: To execute LINQ query please set allowSynchronousQueryExecution true or use GetItemQueryIterator to execute asynchronously
         at Microsoft.Azure.Cosmos.Linq.CosmosLinqQuery`1.GetEnumerator()+MoveNext()
         at HotChocolate.Execution.Processing.Tasks.ResolverTask.<>c__DisplayClass50_0.<ExecuteResolverPipelineAsync>b__0()
         at System.Threading.Tasks.Task`1.InnerInvoke()
         at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
      --- End of stack trace from previous location ---
         at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
         at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
      --- End of stack trace from previous location ---
         at HotChocolate.Execution.Processing.Tasks.ResolverTask.ExecuteResolverPipelineAsync(CancellationToken cancellationToken)
         at HotChocolate.Execution.Processing.Tasks.ResolverTask.TryExecuteAsync(CancellationToken cancellationToken)

Additional Context?

HC should try to load data from the IQuerayble asynchronously rather than synchronously

Version

13.0.5

Blockers to having a nice repository for searching/paging/filtering for Cosmos and HotChocolate

• This issue
• Latest release does not fix GetItemLinqQueryable issue [Still broken 3/2/23] Azure/azure-cosmos-dotnet-v3#3697
• Query: Added remaining Cosmos Type checking functions to CosmosLinqExtensions Azure/azure-cosmos-dotnet-v3#3724
• Add LIKE extension LINQ support Azure/azure-cosmos-dotnet-v3#3725

[onionhammer]

It seems like this is the code to blame, perhaps? Does HotChocolate have a special case for EF Core or are all IQueryables really executed synchronously?

[michaelstaib]

We check, if the queryable also implements IAsyncEnumerable than we will use the async variant. In the case of EFCore, they are implementing IAsyncEnumerable.

[michaelstaib]

Does Cosmos implement IAsyncEnumerable?

[michaelstaib]

Just double checked ... in the case of EFCore you can do the following, and that is what we do:

            if (source is IAsyncEnumerable<TSource> asyncEnumerable)
            {
                return asyncEnumerable;
            }

this is done in a middleware... the resolver task is kind of the last line of defense and there we will execute it in a task if no other way was found in the pipeline.

Looking at the docs the have this weird way with the iterator to fetch it. Strange that they do not implement IAsyncEnumerable.

[michaelstaib]

What can be done are several things.... either a middleware specific for cosmos of a paging provider for cosmos.

[onionhammer]

Yeah, I think cosmos ought to implement Iasyncenumerable.. but you guys do have a ravendb provider, surely cosmos is more popular than that in 2023… right? 😅

Even if Cosmos' IQueryable supported IAsyncEnumerable, it would not be able to support retrieving totalCount efficiently

I ended up writing some middleware to support this kinda, but it would be cool if there was a HC package for cosmos support; would remove a lot of code

[michaelstaib]

Yeah, I think cosmos ought to implement Iasyncenumerable.. but you guys do have a ravendb provider, surely cosmos is more popular than that in 2023… right?

Not sure about that ... the raven community was very active and lots of people wanted support for that. We had also lots of requests for EfCore and MongoDB ... I would say you are the first to ask for cosmos :D

[michaelstaib]

Just checked ... 6 issues including this ... and 5 where asking question for cosmos with EFCore ... so not a lot of demand. Demand as from questions on slack is:

1. Postgres
2. MongoDB
3. RavenDB

[michaelstaib]

But if you want to do the work for the driver we will help you with that. The work for the MartenDB diver was also done by one of our community members. Interested to help on cosmos?

[onionhammer]

@michaelstaib I am interested in contributing it. I'm still struggling to figure out the best way to accomplish it with minimal use of attributes that have to be tacked on