fix(createforecast): Correctly set empty value metadata to NULL (#128)

Author: devsjc

internal/server/postgres/dataserverimpl.go

@@ -182,6 +182,11 @@ func (s *DataPlatformDataServiceServerImpl) CreateForecast(
 			roundedStats[k] = roundedVal
 		}
 
+		// Since CreatePredictedValues uses COPYFROM, manually coerce empty metadata to nil
+		if value.Metadata != nil && len(value.Metadata.Fields) == 0 {
+			value.Metadata = nil
+		}
+
 		var otherStats *structpb.Struct
 
 		if len(roundedStats) > 0 {

internal/server/postgres/dataserverimpl_test.go

@@ -1518,7 +1518,7 @@ func TestCreateForecast(t *testing.T) {
 			HorizonMins:              uint32(i * 30),
 			P50Fraction:              0.0,
 			OtherStatisticsFractions: map[string]float32{},
-			Metadata:                 nil,
+			Metadata:                 &structpb.Struct{},
 		}
 	}
 
@@ -1550,7 +1550,7 @@ func TestCreateForecast(t *testing.T) {
 			},
 		},
 		{
-			name: "Should create forecast with zeroed values",
+			name: "Should create forecast with zeroed values and metadata",
 			req: &pb.CreateForecastRequest{
 				LocationUuid: siteResp.LocationUuid,
 				Forecaster:   fcResp.Forecaster,