Package graphql.incremental

Interface IncrementalExecutionResult

All Superinterfaces:
ExecutionResult
All Known Implementing Classes:
IncrementalExecutionResultImpl
@ExperimentalApi public interface IncrementalExecutionResult extends ExecutionResult
A result that is part of an execution that includes incrementally delivered data (data has been deferred of streamed).

For example, this query 

 query {
   person(id: "cGVvcGxlOjE=") {
     ...HomeWorldFragment @defer(label: "homeWorldDefer")
     name
     films @stream(initialCount: 1, label: "filmsStream") {
       title
     }
   }
 }
 fragment HomeWorldFragment on Person {
   homeWorld {
     name
   }
 }
Could result on an incremental response with the following payloads (in JSON format here for simplicity).

Response 1, the initial response does not contain any deferred or streamed results. 

 {
   "data": {
     "person": {
       "name": "Luke Skywalker",
       "films": [{ "title": "A New Hope" }]
     }
   },
   "hasNext": true
 }
Response 2, contains the defer payload and the first stream payload. 
 {
   "incremental": [
     {
       "label": "homeWorldDefer",
       "path": ["person"],
       "data": { "homeWorld": { "name": "Tatooine" } }
     },
     {
       "label": "filmsStream",
       "path": ["person", "films", 1],
       "items": [{ "title": "The Empire Strikes Back" }]
     }
   ],
   "hasNext": true
 }
Response 3, contains the final stream payload. Note how "hasNext" is "false", indicating this is the final response. 
 {
   "incremental": [
     {
       "label": "filmsStream",
       "path": ["person", "films", 2],
       "items": [{ "title": "Return of the Jedi" }]
     }
   ],
   "hasNext": false
 }

This implementation is based on the state of Defer/Stream PR More specifically at the state of this commit

The execution behaviour should match what we get from running Apollo Server 4.9.5 with graphql-js v17.0.0-alpha.2

  • Method Details

    • hasNext

      boolean hasNext()
      Indicates whether there are pending incremental data.
      Returns:
      "true" if there are incremental data, "false" otherwise.

    • getIncremental

      @Nullable List<IncrementalPayload> getIncremental()
      Returns a list of defer and/or stream payloads that the execution engine decided (for whatever reason) to resolve at the same time as the initial payload.

      (...)this field may appear on both the initial and subsequent values.

      source

      Returns:
      a list of Stream and/or Defer payloads that were resolved at the same time as the initial payload.

    • getIncrementalItemPublisher

      org.reactivestreams.Publisher<DelayedIncrementalPartialResult> getIncrementalItemPublisher()
      This method will return a Publisher of deferred results. No field processing will be done until a Subscriber is attached to this publisher.

      Once a Subscriber is attached the deferred field result processing will be started and published as a series of events.

      Returns:
      a Publisher that clients can subscribe to receive incremental payloads.