Implement top/bottom

pkg/datasource/functions.go

@@ -45,6 +45,8 @@ var seriesFuncMap map[string]DataProcessingFunc
 
 var aggFuncMap map[string]AggDataProcessingFunc
 
+var filterFuncMap map[string]AggDataProcessingFunc
+
 var frontendFuncMap map[string]bool
 
 func init() {
@@ -61,6 +63,11 @@ func init() {
 		"percentileAgg": applyPercentileAgg,
 	}
 
+	filterFuncMap = map[string]AggDataProcessingFunc{
+		"top":    applyTop,
+		"bottom": applyBottom,
+	}
+
 	// Functions processing on the frontend
 	frontendFuncMap = map[string]bool{
 		"setAlias":        true,
@@ -85,6 +92,12 @@ func applyFunctions(series []*timeseries.TimeSeriesData, functions []QueryFuncti
 				return nil, err
 			}
 			series = result
+		} else if applyFilterFunc, ok := filterFuncMap[f.Def.Name]; ok {
+			result, err := applyFilterFunc(series, f.Params...)
+			if err != nil {
+				return nil, err
+			}
+			series = result
 		} else if _, ok := frontendFuncMap[f.Def.Name]; ok {
 			continue
 		} else {
@@ -207,6 +220,30 @@ func applyPercentileAgg(series []*timeseries.TimeSeriesData, params ...interface
 	return []*timeseries.TimeSeriesData{aggregatedSeries}, nil
 }
 
+func applyTop(series []*timeseries.TimeSeriesData, params ...interface{}) ([]*timeseries.TimeSeriesData, error) {
+	n, err := MustFloat64(params[0])
+	pAgg, err := MustString(params[1])
+	if err != nil {
+		return nil, errParsingFunctionParam(err)
+	}
+
+	aggFunc := getAggFunc(pAgg)
+	filteredSeries := timeseries.Filter(series, int(n), "top", aggFunc)
+	return filteredSeries, nil
+}
+
+func applyBottom(series []*timeseries.TimeSeriesData, params ...interface{}) ([]*timeseries.TimeSeriesData, error) {
+	n, err := MustFloat64(params[0])
+	pAgg, err := MustString(params[1])
+	if err != nil {
+		return nil, errParsingFunctionParam(err)
+	}
+
+	aggFunc := getAggFunc(pAgg)
+	filteredSeries := timeseries.Filter(series, int(n), "bottom", aggFunc)
+	return filteredSeries, nil
+}
+
 func getAggFunc(agg string) timeseries.AggFunc {
 	switch agg {
 	case "avg":

pkg/timeseries/timeseries.go

@@ -94,6 +94,34 @@ func (ts TimeSeries) Transform(transformFunc TransformFunc) TimeSeries {
 	return ts
 }
 
+func Filter(series []*TimeSeriesData, n int, order string, aggFunc AggFunc) []*TimeSeriesData {
+	aggregatedSeries := make([]TimeSeries, len(series))
+	for i, s := range series {
+		aggregatedSeries[i] = s.TS.GroupByRange(aggFunc)
+	}
+
+	// Sort by aggregated value
+	sort.Slice(series, func(i, j int) bool {
+		if len(aggregatedSeries[i]) > 0 && len(aggregatedSeries[j]) > 0 {
+			return *aggregatedSeries[i][0].Value < *aggregatedSeries[j][0].Value
+		} else if len(aggregatedSeries[j]) > 0 {
+			return true
+		}
+		return false
+	})
+
+	filteredSeries := make([]*TimeSeriesData, n)
+	for i := 0; i < n; i++ {
+		if order == "top" {
+			filteredSeries[i] = series[len(aggregatedSeries)-1-i]
+		} else if order == "bottom" {
+			filteredSeries[i] = series[i]
+		}
+	}
+
+	return filteredSeries
+}
+
 func AggregateBy(series []*TimeSeriesData, interval time.Duration, aggFunc AggFunc) *TimeSeriesData {
 	aggregatedSeries := NewTimeSeries()