func NewAggregatorEngine(query *parser.SelectQuery, next Processor) (*AggregatorEngine, error) { ae := &AggregatorEngine{ next: next, seriesStates: make(map[string]*SeriesState), ascending: query.Ascending, } var err error ae.duration, ae.irregularInterval, err = query.GetGroupByClause().GetGroupByTime() if err != nil { return nil, err } ae.aggregators = []Aggregator{} for _, value := range query.GetColumnNames() { if !value.IsFunctionCall() { continue } lowerCaseName := strings.ToLower(value.Name) initializer := registeredAggregators[lowerCaseName] if initializer == nil { return nil, common.NewQueryError(common.InvalidArgument, fmt.Sprintf("Unknown function %s", value.Name)) } aggregator, err := initializer(query, value, query.GetGroupByClause().FillValue) if err != nil { return nil, common.NewQueryError(common.InvalidArgument, fmt.Sprintf("%s", err)) } ae.aggregators = append(ae.aggregators, aggregator) } for _, elem := range query.GetGroupByClause().Elems { if elem.IsFunctionCall() { continue } ae.elems = append(ae.elems, elem) } ae.isFillQuery = query.GetGroupByClause().FillWithZero // This is a special case for issue #426. If the start time is // specified and there's a group by clause and fill with zero, then // we need to fill the entire range from start time to end time if query.IsStartTimeSpecified() && ae.duration != nil && ae.isFillQuery { ae.startTimeSpecified = true ae.startTime = query.GetStartTime().Truncate(*ae.duration).UnixNano() / 1000 ae.endTime = query.GetEndTime().Truncate(*ae.duration).UnixNano() / 1000 } ae.initializeFields() return ae, nil }