Differentiating the types of existence checks in v2/observation and including them in usage logger

internal/log/usagelogger.go

@@ -37,6 +37,8 @@ type StatVarLog struct {
 	StatVarDCID string      `json:"stat_var_dcid"`
 	// List of all facets that provided results for the given statVar.
 	Facets      []*FacetLog `json:"facets"`
+	// The number of entities included in this statVar's results. 
+	NumSeries 	int        `json:"num_series"`
 }
 
 // Full log with all information for the current query.
@@ -123,6 +125,8 @@ func MakeStatVarLogs(observationResponse *pbv2.ObservationResponse) ([]*StatVarL
 		if _, ok := statVarsByDcid[variable]; !ok {
 			statVarsByDcid[variable] = &StatVarLog{
 				StatVarDCID: variable,
+				// capturing the number of entities for this statVar
+				NumSeries: len(varObs.ByEntity),
 			}
 		}
 

internal/server/handler_v2_test.go

@@ -182,7 +182,7 @@ func TestObservationInternal(t *testing.T) {
 					Dcids: []string{"country/USA"},
 				},
 			},
-			shared.QueryTypeExistence,
+			shared.QueryTypeExistenceByEntity,
 			&pbv2.ObservationResponse{
 				ByVariable: map[string]*pbv2.VariableObservation{
 					"Count_Person": {}, 

internal/server/v2/observation/observation.go

@@ -167,13 +167,13 @@ func ObservationCore(
 				// Have both entity.dcids and variable.dcids. Check existence cache.
 				res, err := Existence(
 					ctx, store, cachedata, variable.GetDcids(), entity.GetDcids())
-				return res, shared.QueryTypeExistence, err
+				return res, shared.QueryTypeExistenceByVar, err
 			}
 			// TODO: Support appending entities from entity.expression
 			// Only have entity.dcids, fetch variables for each entity.
 			res, err := Variable(ctx, store, entity.GetDcids())
 
-			return res, shared.QueryTypeExistence, err
+			return res, shared.QueryTypeExistenceByEntity, err
 		}
 	}
 	return &pbv2.ObservationResponse{}, "", nil

internal/server/v2/shared/shared.go

@@ -43,8 +43,10 @@ const (
 	QueryTypeValue QueryType = "value"
 	// Fetches information about a given facet.
 	QueryTypeFacet QueryType = "facet"
-	// Checks if a given statVar has information for a given entity.
-	QueryTypeExistence QueryType = "existence"
+	// Checks if a given statVar has information for a given set of entities AND variables.
+	QueryTypeExistenceByVar QueryType = "existence-var"
+	// Checks if a given statVar has ANY statVars for a given set of entities
+	QueryTypeExistenceByEntity QueryType = "existence-entity"
 	// Calculates a value from other fetches.
 	QueryTypeDerived QueryType = "derived"
 )