MB-57228: Avoid double counting when sorting by field for faceted que…

…ry (#1836) (#1842)

Co-authored-by: Aditi Ahuja <48997495+metonymic-smokey@users.noreply.github.com>

search/collector/topn.go

@@ -357,7 +357,20 @@ func (hc *TopNCollector) visitFieldTerms(reader index.IndexReader, d *search.Doc
 // SetFacetsBuilder registers a facet builder for this collector
 func (hc *TopNCollector) SetFacetsBuilder(facetsBuilder *search.FacetsBuilder) {
 	hc.facetsBuilder = facetsBuilder
-	hc.neededFields = append(hc.neededFields, hc.facetsBuilder.RequiredFields()...)
+	fieldsRequiredForFaceting := facetsBuilder.RequiredFields()
+	// for each of these fields, append only if not already there in hc.neededFields.
+	for _, field := range fieldsRequiredForFaceting {
+		found := false
+		for _, neededField := range hc.neededFields {
+			if field == neededField {
+				found = true
+				break
+			}
+		}
+		if !found {
+			hc.neededFields = append(hc.neededFields, field)
+		}
+	}
 }
 
 // finalizeResults starts with the heap containing the final top size+skip

search/collector/topn_test.go

@@ -19,7 +19,9 @@ import (
 	"context"
 	"testing"
 
+	"github.com/blevesearch/bleve/v2/index/scorch"
 	"github.com/blevesearch/bleve/v2/search"
+	"github.com/blevesearch/bleve/v2/search/facet"
 	index "github.com/blevesearch/bleve_index_api"
 )
 
@@ -724,6 +726,48 @@ func TestCollectorChaining(t *testing.T) {
 	}
 }
 
+func setupIndex(t *testing.T) index.Index {
+	analysisQueue := index.NewAnalysisQueue(1)
+	i, err := scorch.NewScorch(
+		scorch.Name,
+		map[string]interface{}{
+			"path": "",
+		},
+		analysisQueue)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = i.Open()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	return i
+}
+
+func TestSetFacetsBuilder(t *testing.T) {
+	// Field common to both sorting and faceting.
+	sortFacetsField := "locations"
+
+	coll := NewTopNCollector(10, 0, search.SortOrder{&search.SortField{Field: sortFacetsField}})
+
+	i := setupIndex(t)
+	indexReader, err := i.Reader()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	fb := search.NewFacetsBuilder(indexReader)
+	facetBuilder := facet.NewTermsFacetBuilder(sortFacetsField, 100)
+	fb.Add("locations_facet", facetBuilder)
+	coll.SetFacetsBuilder(fb)
+
+	// Should not duplicate the "locations" field in the collector.
+	if len(coll.neededFields) != 1 || coll.neededFields[0] != sortFacetsField {
+		t.Errorf("expected fields in collector: %v, observed: %v", []string{sortFacetsField}, coll.neededFields)
+	}
+}
+
 func BenchmarkTop10of0Scores(b *testing.B) {
 	benchHelper(0, func() search.Collector {
 		return NewTopNCollector(10, 0, search.SortOrder{&search.SortScore{Desc: true}})

search_test.go

@@ -45,6 +45,77 @@ import (
 	"github.com/blevesearch/bleve/v2/search/query"
 )
 
+func TestSortedFacetedQuery(t *testing.T) {
+	tmpIndexPath := createTmpIndexPath(t)
+	defer cleanupTmpIndexPath(t, tmpIndexPath)
+
+	indexMapping := NewIndexMapping()
+	indexMapping.TypeField = "type"
+	indexMapping.DefaultAnalyzer = "en"
+	documentMapping := NewDocumentMapping()
+	indexMapping.AddDocumentMapping("hotel", documentMapping)
+
+	contentFieldMapping := NewTextFieldMapping()
+	contentFieldMapping.Index = true
+	contentFieldMapping.DocValues = true
+	documentMapping.AddFieldMappingsAt("content", contentFieldMapping)
+	documentMapping.AddFieldMappingsAt("country", contentFieldMapping)
+
+	index, err := New(tmpIndexPath, indexMapping)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		err := index.Close()
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	index.Index("1", map[string]interface{}{
+		"country": "india",
+		"content": "k",
+	})
+	index.Index("2", map[string]interface{}{
+		"country": "india",
+		"content": "l",
+	})
+	index.Index("3", map[string]interface{}{
+		"country": "india",
+		"content": "k",
+	})
+
+	d, err := index.DocCount()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if d != 3 {
+		t.Errorf("expected 3, got %d", d)
+	}
+
+	query := NewMatchPhraseQuery("india")
+	query.SetField("country")
+	searchRequest := NewSearchRequest(query)
+	searchRequest.SortBy([]string{"content"})
+	fr := NewFacetRequest("content", 100)
+	searchRequest.AddFacet("content_facet", fr)
+
+	searchResults, err := index.Search(searchRequest)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expectedResults := map[string]int{"k": 2, "l": 1}
+
+	for _, v := range searchResults.Facets {
+		for _, v1 := range v.Terms.Terms() {
+			if v1.Count != expectedResults[v1.Term] {
+				t.Errorf("expected %d, got %d", expectedResults[v1.Term], v1.Count)
+			}
+		}
+	}
+}
+
 func TestSearchResultString(t *testing.T) {
 
 	tests := []struct {