Add other buckets to Filters Aggregation

This commit adds the two fields `other_buckets` (true/false) and
`other_buckets_key` (string) to the Filters Aggregation.

For details, see the documentation at
https://www.elastic.co/guide/en/elasticsearch/reference/7.8/search-aggregations-bucket-filters-aggregation.html#other-bucket

Close #1350

Author: olivere

search_aggs_bucket_filters.go

@@ -19,6 +19,8 @@ import "errors"
 type FiltersAggregation struct {
 	unnamedFilters  []Query
 	namedFilters    map[string]Query
+	otherBucket     *bool
+	otherBucketKey  string
 	subAggregations map[string]Aggregation
 	meta            map[string]interface{}
 }
@@ -55,6 +57,20 @@ func (a *FiltersAggregation) FilterWithName(name string, filter Query) *FiltersA
 	return a
 }
 
+// OtherBucket indicates whether to include a bucket for documents not
+// matching any filter.
+func (a *FiltersAggregation) OtherBucket(otherBucket bool) *FiltersAggregation {
+	a.otherBucket = &otherBucket
+	return a
+}
+
+// OtherBucketKey sets the key to use for the bucket for documents not
+// matching any filter.
+func (a *FiltersAggregation) OtherBucketKey(key string) *FiltersAggregation {
+	a.otherBucketKey = key
+	return a
+}
+
 // SubAggregation adds a sub-aggregation to this aggregation.
 func (a *FiltersAggregation) SubAggregation(name string, subAggregation Aggregation) *FiltersAggregation {
 	a.subAggregations[name] = subAggregation
@@ -116,6 +132,13 @@ func (a *FiltersAggregation) Source() (interface{}, error) {
 		filters["filters"] = dict
 	}
 
+	if v := a.otherBucket; v != nil {
+		filters["other_bucket"] = *v
+	}
+	if v := a.otherBucketKey; v != "" {
+		filters["other_bucket_key"] = v
+	}
+
 	// AggregationBuilder (SubAggregations)
 	if len(a.subAggregations) > 0 {
 		aggsMap := make(map[string]interface{})

search_aggs_bucket_filters_test.go

@@ -59,6 +59,27 @@ func TestFiltersAggregationWithKeyedAndNonKeyedFilters(t *testing.T) {
 	}
 }
 
+func TestFiltersAggregationWithOtherBuckets(t *testing.T) {
+	agg := NewFiltersAggregation().
+		FilterWithName("errors", NewMatchQuery("body", "error")).
+		FilterWithName("warnings", NewMatchQuery("body", "warnings")).
+		OtherBucket(true).
+		OtherBucketKey("other")
+	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 := `{"filters":{"filters":{"errors":{"match":{"body":{"query":"error"}}},"warnings":{"match":{"body":{"query":"warnings"}}}},"other_bucket":true,"other_bucket_key":"other"}}`
+	if got != expected {
+		t.Errorf("expected\n%s\n,got:\n%s", expected, got)
+	}
+}
+
 func TestFiltersAggregationWithSubAggregation(t *testing.T) {
 	avgPriceAgg := NewAvgAggregation().Field("price")
 	f1 := NewRangeQuery("stock").Gt(0)

search_aggs_test.go

@@ -154,7 +154,8 @@ func TestAggs(t *testing.T) {
 	builder = builder.Aggregation("centroid", geoCentroidAgg)
 	// Unnamed filters
 	countByUserAgg := NewFiltersAggregation().
-		Filters(NewTermQuery("user", "olivere"), NewTermQuery("user", "sandrae"))
+		Filters(NewTermQuery("user", "olivere"), NewTermQuery("user", "sandrae")).
+		OtherBucket(true).OtherBucketKey("other")
 	builder = builder.Aggregation("countByUser", countByUserAgg)
 	// Named filters
 	countByUserAgg2 := NewFiltersAggregation().
@@ -1172,8 +1173,8 @@ func TestAggs(t *testing.T) {
 		if agg == nil {
 			t.Fatalf("expected != nil; got: nil")
 		}
-		if len(agg.Buckets) != 2 {
-			t.Fatalf("expected %d; got: %d", 2, len(agg.Buckets))
+		if len(agg.Buckets) != 3 {
+			t.Fatalf("expected %d; got: %d", 3, len(agg.Buckets))
 		}
 		if len(agg.NamedBuckets) != 0 {
 			t.Fatalf("expected %d; got: %d", 0, len(agg.NamedBuckets))
@@ -1184,6 +1185,9 @@ func TestAggs(t *testing.T) {
 		if agg.Buckets[1].DocCount != 1 {
 			t.Errorf("expected %d; got: %d", 1, agg.Buckets[1].DocCount)
 		}
+		if agg.Buckets[1].DocCount != 0 {
+			t.Errorf("expected %d; got: %d", 0, agg.Buckets[2].DocCount)
+		}
 	}
 
 	// Filters agg "countByUser2" (named)