QueryProcessing: Observable query interface and RxJS for query & stream processing (#18899)

* I needed to learn some rxjs and understand this more, so just playing around

* Updated

* Removed all the complete calls

* Refactoring

* StreamHandler -> observable start

* progress

* simple singal works

* Handle update time range

* added error handling

* wrap old function

* minor changes

* handle data format in the subscribe function

* Use replay subject to return last value to subscribers

* Set loading state after no response in 50ms

* added missing file

* updated comment

* Added cancelation of network requests

* runRequest: Added unit test scenario framework

* Progress on tests

* minor refactor of unit tests

* updated test

* removed some old code

* Shared queries work again, and also became so much simplier

* unified query and observe methods

* implict any fix

* Fixed closed subject issue

* removed comment

* Use last returned data for loading state

* WIP: Explore to runRequest makover step1

* Minor progress

* Minor progress on explore and runRequest

* minor progress

* Things are starting to work in explore

* Updated prometheus to use new observable query response, greatly simplified code

* Revert refId change

* Found better solution for key/refId/requestId problem

* use observable with loki

* tests compile

* fix loki query prep

* Explore: correct first response handling

* Refactorings

* Refactoring

* Explore: Fixes LoadingState and GraphResults between runs (#18986)

* Refactor: Adds state to DataQueryResponse

* Fix: Fixes so we do not empty results before new data arrives
Fixes: #17409

* Transformations work

* observable test data

* remove single() from loki promise

* Fixed comment

* Explore: Fixes failing Loki and Prometheus unit tests (#18995)

* Tests: Makes datasource tests work again

* Fix: Fixes loki datasource so highligthing works

* Chore: Runs Prettier

* Fixed query runner tests

* Delay loading state indication to 200ms

* Fixed test

* fixed unit tests

* Clear cached calcs

* Fixed bug getProcesedDataFrames

* Fix the correct test is a better idea

* Fix: Fixes so queries in Explore are only run if Graph/Table is shown (#19000)

* Fix: Fixes so queries in Explore are only run if Graph/Table is shown
Fixes: #18618

* Refactor: Removes unnecessary condition

* PanelData: provide legacy data only when needed  (#19018)

* no legacy

* invert logic... now compiles

* merge getQueryResponseData and getDataRaw

* update comment about query editor

* use single getData() function

* only send legacy when it is used in explore

* pre process rather than post process

* pre process rather than post process

* Minor refactoring

* Add missing tags to test datasource response

* MixedDatasource: Adds query observable pattern to MixedDatasource (#19037)

* start mixed datasource

* Refactor: Refactors into observable parttern

* Tests: Fixes tests

* Tests: Removes console.log

* Refactor: Adds unique requestId

public/app/features/explore/utils/ResultProcessor.test.ts

@@ -67,20 +67,20 @@ const testContext = (options: any = {}) => {
 describe('ResultProcessor', () => {
   describe('constructed without result', () => {
     describe('when calling getGraphResult', () => {
-      it('then it should return an empty array', () => {
+      it('then it should return null', () => {
         const { resultProcessor } = testContext({ dataFrames: [] });
         const theResult = resultProcessor.getGraphResult();
 
-        expect(theResult).toEqual([]);
+        expect(theResult).toEqual(null);
       });
     });
 
     describe('when calling getTableResult', () => {
-      it('then it should return an empty TableModel', () => {
+      it('then it should return null', () => {
         const { resultProcessor } = testContext({ dataFrames: [] });
         const theResult = resultProcessor.getTableResult();
 
-        expect(theResult).toEqual(new TableModel());
+        expect(theResult).toEqual(null);
       });
     });
 

public/app/features/explore/utils/ResultProcessor.ts

@@ -11,11 +11,15 @@ export class ResultProcessor {
 
   getGraphResult(): GraphSeriesXY[] {
     if (this.state.mode !== ExploreMode.Metrics) {
-      return [];
+      return null;
     }
 
     const onlyTimeSeries = this.dataFrames.filter(isTimeSeries);
 
+    if (onlyTimeSeries.length === 0) {
+      return null;
+    }
+
     return getGraphSeriesModel(
       onlyTimeSeries,
       {},
@@ -26,7 +30,7 @@ export class ResultProcessor {
 
   getTableResult(): TableModel {
     if (this.state.mode !== ExploreMode.Metrics) {
-      return new TableModel();
+      return null;
     }
 
     // For now ignore time series
@@ -34,6 +38,10 @@ export class ResultProcessor {
     // Ignore time series only for prometheus
     const onlyTables = this.dataFrames.filter(frame => !isTimeSeries(frame));
 
+    if (onlyTables.length === 0) {
+      return null;
+    }
+
     const tables = onlyTables.map(frame => {
       const { fields } = frame;
       const fieldCount = fields.length;