Query a WFS Layer with Feature Reduction Cluster

[ShariMeier]

Hi there, 

I'm currently working with a WFS Layer with a feature reduction to create clusters. 

Now I need to identify on which cluster a user has clicked on the map and which objects are included in this cluster. As I made the feature reduction on the client-side - I assumed that I needed to choose a query method that does the query on client-side. I tried it directly on the layerView and the WFS layer ( see code example below).

However, both ways don't recognize the cluster. But they return the points behind the cluster or, more precisely, in the cluster if I accidentally click on the exact spot where original points were when I'm trying to select the cluster. What am I missing here?

Thanks in advance for your tips and help!

Best wishes, 
Shari

//query on WFSLayerView
const query = (layerView.layer as WFSLayer).createQuery();
query.geometry = point;
query.distance = distance;
query.units = 'meters';
query.spatialRelationship = 'intersects';
query.returnGeometry = true;
query.outFields = ['*'];

(layerView as WFSLayerView).queryFeatures(query).then(function (results) {
console.log(results.features);
});

//query on WFSLayer
return fromPromise(
(layer as WFSLayer).queryFeatures({
geometry: point,
 distance: distance,
 units: 'meters',
 spatialRelationship: 'intersects',
 returnGeometry: true,
 outFields: ['*'],
 }),
).pipe(
map((featureSet: FeatureSet) => {
console.log(featureSet.features);
 }),
);

[ShariMeier · Accepted solution]

We solved this as follows: with a hit test, we ask for the clicked clusters and then execute a query on the WFSLayerView with the "aggregateIds". This returns all objects within the cluster, which we then can use for other stuff. 

switchMap(([layerView]) => {
  wfsLayerView = layerView;
  const opts = { include: layer };
  return from(this.mainMapService.mapView.hitTest(screenPoint, opts)).pipe(
    map((response: HitTestResult) => {
      return response;
    }),
  );
}),
switchMap((response) => {
  if (response.results.length) {
    const graphic = response.results[0].graphic;
    if (graphic.isAggregate) {
      //cluster is clicked, we need to query for all objects inside the cluster
      const query = wfsLayerView.createQuery();
      query.aggregateIds = [graphic.getObjectId()];
      return from(wfsLayerView.queryFeatures(query)).pipe(
        map((result) => {
          console.log(result.features);
          return result.features;
        }),
      );
    } else {
      // single point is clicked
      return of([graphic]);
    }
  }
  return of(null);
}),

[RoyJackson_AlertMedia]

Very nice!   Note if you do not pass aggregateIds as an array of values, and only have a single objectId value, you will get every feature in the layer back 🙂