aggs: Add percentiles method

This commit fixes #1045 by adding a percentiles method and correctly
handle the `tdigest` and `hdr` case.

Close #1045

Author: olivere

search_aggs_metrics_percentiles.go

@@ -12,21 +12,24 @@ package elastic
 //
 // See: https://www.elastic.co/guide/en/elasticsearch/reference/6.7/search-aggregations-metrics-percentile-aggregation.html
 type PercentilesAggregation struct {
-	field           string
-	script          *Script
-	format          string
-	missing         interface{}
-	subAggregations map[string]Aggregation
-	meta            map[string]interface{}
-	percentiles     []float64
-	compression     *float64
-	estimator       string
+	field                          string
+	script                         *Script
+	format                         string
+	missing                        interface{}
+	subAggregations                map[string]Aggregation
+	meta                           map[string]interface{}
+	percentiles                    []float64
+	method                         string
+	compression                    *float64
+	numberOfSignificantValueDigits *int
+	estimator                      string
 }
 
 func NewPercentilesAggregation() *PercentilesAggregation {
 	return &PercentilesAggregation{
 		subAggregations: make(map[string]Aggregation),
 		percentiles:     make([]float64, 0),
+		method:          "tdigest",
 	}
 }
 
@@ -66,11 +69,22 @@ func (a *PercentilesAggregation) Percentiles(percentiles ...float64) *Percentile
 	return a
 }
 
+// Method is the percentiles method, which can be "tdigest" (default) or "hdr".
+func (a *PercentilesAggregation) Method(method string) *PercentilesAggregation {
+	a.method = method
+	return a
+}
+
 func (a *PercentilesAggregation) Compression(compression float64) *PercentilesAggregation {
 	a.compression = &compression
 	return a
 }
 
+func (a *PercentilesAggregation) NumberOfSignificantValueDigits(digits int) *PercentilesAggregation {
+	a.numberOfSignificantValueDigits = &digits
+	return a
+}
+
 func (a *PercentilesAggregation) Estimator(estimator string) *PercentilesAggregation {
 	a.estimator = estimator
 	return a
@@ -115,8 +129,19 @@ func (a *PercentilesAggregation) Source() (interface{}, error) {
 	if len(a.percentiles) > 0 {
 		opts["percents"] = a.percentiles
 	}
-	if a.compression != nil {
-		opts["compression"] = *a.compression
+	switch a.method {
+	case "tdigest":
+		if c := a.compression; c != nil {
+			opts[a.method] = map[string]interface{}{
+				"compression": *c,
+			}
+		}
+	case "hdr":
+		if n := a.numberOfSignificantValueDigits; n != nil {
+			opts[a.method] = map[string]interface{}{
+				"number_of_significant_value_digits": *n,
+			}
+		}
 	}
 	if a.estimator != "" {
 		opts["estimator"] = a.estimator

search_aggs_metrics_percentiles_test.go

@@ -79,3 +79,41 @@ func TestPercentilesAggregationWithMetaData(t *testing.T) {
 		t.Errorf("expected\n%s\n,got:\n%s", expected, got)
 	}
 }
+
+func TestPercentilesAggregationWithCompression(t *testing.T) {
+	agg := NewPercentilesAggregation().Field("load_time").Compression(200.0)
+	src, err := agg.Source()
+	if err != nil {
+		t.Fatal(err)
+	}
+	data, err := json.Marshal(src)
+	if err != nil {
+		t.Fatalf("marshaling to JSON failed: %v", err)
+	}
+	got := string(data)
+	expected := `{"percentiles":{"field":"load_time","tdigest":{"compression":200}}}`
+	if got != expected {
+		t.Errorf("expected\n%s\n,got:\n%s", expected, got)
+	}
+}
+
+func TestPercentilesAggregationWithNumberOfSignificantValueDigits(t *testing.T) {
+	agg := NewPercentilesAggregation().
+		Field("load_time").
+		Percentiles(95, 99, 99.9).
+		Method("hdr").
+		NumberOfSignificantValueDigits(5)
+	src, err := agg.Source()
+	if err != nil {
+		t.Fatal(err)
+	}
+	data, err := json.Marshal(src)
+	if err != nil {
+		t.Fatalf("marshaling to JSON failed: %v", err)
+	}
+	got := string(data)
+	expected := `{"percentiles":{"field":"load_time","hdr":{"number_of_significant_value_digits":5},"percents":[95,99,99.9]}}`
+	if got != expected {
+		t.Errorf("expected\n%s\n,got:\n%s", expected, got)
+	}
+}