Use sql query to leverage sqlite speed

server/services/sensor_values_service.go

@@ -14,13 +14,6 @@ type sensorValue struct {
 	Value     float64 `json:"value"`
 }
 
-func min(a, b int64) int64 {
-	if a < b {
-		return a
-	}
-	return b
-}
-
 func (s *SensorValuesService) Push(sensorId int64, value float64) (int64, error) {
 	res, err := s.ctx.DB.Exec("INSERT INTO sensor_values (timestamp, sensor_id, value) VALUES (?, ?, ?)", time.Now().Unix(), sensorId, value)
 
@@ -32,36 +25,7 @@ func (s *SensorValuesService) Push(sensorId int64, value float64) (int64, error)
 }
 
 func (s *SensorValuesService) GetList(sensorId int64, from int64, to int64) ([]sensorValue, error) {
-	intervalSize := to - from
-	batchSize := intervalSize
-
-	if intervalSize > 100*24*60 {
-		batchSize = 24 * 60
-	}
-
-	values := make([]sensorValue, 0)
-	current := from
-
-	for current < to {
-		nextValue := min(to, current+batchSize)
-
-		batchValues, err := s.getValueItems(sensorId, current, nextValue)
-
-		if err != nil {
-			return nil, err
-		}
-
-		sum := 0.0
-
-		for _, item := range batchValues {
-			sum += item.Value
-		}
-
-		values = append(values, sensorValue{Timestamp: int64((nextValue + current) / 2.0), Value: sum / float64(len(batchValues))})
-		current += batchSize
-	}
-
-	return values, nil
+	return s.getValueItems(sensorId, from, to, getAutoSensorValuesInterval(from, to))
 }
 
 func (s *SensorValuesService) GetLatest(sensorId int64, to int64) (*sensorValue, error) {
@@ -77,10 +41,47 @@ func (s *SensorValuesService) GetLatest(sensorId int64, to int64) (*sensorValue,
 	return &value, nil
 }
 
-func (s *SensorValuesService) getValueItems(sensorId int64, from int64, to int64) ([]sensorValue, error) {
+func (s *SensorValuesService) getValueListQuery(sensorId int64, from int64, to int64, divide int64) (*sql.Rows, error) {
+	if divide == 1 {
+		return s.ctx.DB.Query("SELECT timestamp, value FROM sensor_values WHERE sensor_id = ? AND timestamp > ? AND timestamp < ? ORDER BY timestamp ASC", sensorId, from, to)
+	}
+
+	return s.ctx.DB.Query(
+		"SELECT (timestamp/?)*?, AVG(value) FROM sensor_values WHERE sensor_id = ? AND timestamp > ? AND timestamp < ? GROUP BY (timestamp/?) ORDER BY timestamp ASC",
+		divide,
+		divide,
+		sensorId,
+		from,
+		to,
+		divide,
+	)
+}
+
+func getAutoSensorValuesInterval(from int64, to int64) int64 {
+	diff := to - from
+
+	// 360 days -> 1 day interval
+	if diff > 360*24*60*60 {
+		return 24 * 60 * 60
+	}
+
+	// 160 days -> 1 hour interval
+	if diff > 160*24*60*60 {
+		return 60 * 60
+	}
+
+	// 80 days -> 10 minutes
+	if diff > 80*24*60*60 {
+		return 10 * 60
+	}
+
+	return 1
+}
+
+func (s *SensorValuesService) getValueItems(sensorId int64, from int64, to int64, divide int64) ([]sensorValue, error) {
 	values := make([]sensorValue, 0)
 
-	rows, err := s.ctx.DB.Query("SELECT timestamp, value FROM sensor_values WHERE sensor_id = ? AND timestamp > ? AND timestamp < ? ORDER BY timestamp ASC", sensorId, from, to)
+	rows, err := s.getValueListQuery(sensorId, from, to, divide)
 
 	if err != nil {
 		if err == sql.ErrNoRows {