fix score boosting issues

While investigating the behavior of several queries using
the query boost capability a few issues were found.

First, an optimization in the boolean query, would replace
the boolean searcher with internal "should" searcher, in
the case where it was the only one (no "must" or "must not").
This optimization is valid, but as implemented today, it looses
track of the users boost.  As this seems to be a minor
optimization, it is temporarily disabled to allow for correct
boosting behavior.

Second, the boolean searcher, which by default will use a
composite scorer (sum constituent scores), was ignoring the
user requested boost value.  A new boosting variant of the
composite scorer is introduced.  This variant first sums
the scores, then multiplies by the boost.

Third, the numeric range searcher was defaulting to a constant
score of 1.0, and it too ignored the requested boost value.  The
code has been updated to return a constant score equal to the
boost (1.0 * boost).

query.go

@@ -208,9 +208,10 @@ func (q *BooleanQuery) Searcher(i search.Reader, options search.SearcherOptions)
 	if mustSearcher == nil && shouldSearcher == nil && mustNotSearcher == nil {
 		// if all 3 are nil, return MatchNone
 		return searcher.NewMatchNoneSearcher(i, options)
-	} else if mustSearcher == nil && shouldSearcher != nil && mustNotSearcher == nil {
-		// optimization, if only should searcher, just return it instead
-		return shouldSearcher, nil
+		// } else if mustSearcher == nil && shouldSearcher != nil && mustNotSearcher == nil {
+		//	DISABLED optimization, if only should searcher, just return it instead
+		//  While logically correct, returning the shouldSearcher looses the desired boost.
+		//	return shouldSearcher, nil
 	} else if mustSearcher == nil && shouldSearcher == nil && mustNotSearcher != nil {
 		// if only mustNotSearcher, start with MatchAll
 		var err error
@@ -221,7 +222,7 @@ func (q *BooleanQuery) Searcher(i search.Reader, options search.SearcherOptions)
 	}
 
 	if q.scorer == nil {
-		q.scorer = similarity.NewCompositeSumScorer()
+		q.scorer = similarity.NewCompositeSumScorerWithBoost(q.boost.Value())
 	}
 
 	return searcher.NewBooleanSearcher(mustSearcher, shouldSearcher, mustNotSearcher, q.scorer, options)
@@ -1143,7 +1144,7 @@ func (q *NumericRangeQuery) Searcher(i search.Reader, options search.SearcherOpt
 		field = options.DefaultSearchField
 	}
 	if q.scorer == nil {
-		q.scorer = similarity.ConstantScorer(1)
+		q.scorer = similarity.ConstantScorer(q.boost.Value())
 	}
 	return searcher.NewNumericRangeSearcher(i, q.min, q.max, q.inclusiveMin, q.inclusiveMax, field,
 		q.boost.Value(), q.scorer, similarity.NewCompositeSumScorer(), options)

search/similarity/composite.go

@@ -14,20 +14,32 @@
 
 package similarity
 
-import "github.com/blugelabs/bluge/search"
+import (
+	"github.com/blugelabs/bluge/search"
+)
 
-type CompositeSumScorer struct{}
+type CompositeSumScorer struct {
+	boost float64
+}
 
 func NewCompositeSumScorer() *CompositeSumScorer {
-	return &CompositeSumScorer{}
+	return &CompositeSumScorer{
+		boost: 1.0,
+	}
+}
+
+func NewCompositeSumScorerWithBoost(boost float64) *CompositeSumScorer {
+	return &CompositeSumScorer{
+		boost: boost,
+	}
 }
 
 func (c *CompositeSumScorer) ScoreComposite(constituents []*search.DocumentMatch) float64 {
 	var rv float64
 	for _, constituent := range constituents {
 		rv += constituent.Score
 	}
-	return rv
+	return rv * c.boost
 }
 
 func (c *CompositeSumScorer) ExplainComposite(constituents []*search.DocumentMatch) *search.Explanation {
@@ -37,7 +49,16 @@ func (c *CompositeSumScorer) ExplainComposite(constituents []*search.DocumentMat
 		sum += constituent.Score
 		children = append(children, constituent.Explanation)
 	}
-	return search.NewExplanation(sum,
-		"sum of:",
-		children...)
+	if c.boost == 1 {
+		return search.NewExplanation(sum,
+			"sum of:",
+			children...)
+	}
+
+	return search.NewExplanation(sum*c.boost,
+		"computed as boost * sum",
+		search.NewExplanation(c.boost, "boost"),
+		search.NewExplanation(sum,
+			"sum of:",
+			children...))
 }

search_test.go

@@ -1271,3 +1271,112 @@ func TestAllMatchesWithAggregationIssue31(t *testing.T) {
 	// should not panic with the fix
 	request.AddAggregation("score", aggregations.MaxStartingAt(search.DocumentScore(), 0))
 }
+
+func TestNumericRangeSearchBoost(t *testing.T) {
+	tmpIndexPath := createTmpIndexPath(t)
+	defer cleanupTmpIndexPath(t, tmpIndexPath)
+
+	config := DefaultConfig(tmpIndexPath)
+	indexWriter, err := OpenWriter(config)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	doc := NewDocument("doc").
+		AddField(NewNumericField("age", 25.0))
+
+	batch := NewBatch()
+	batch.Update(doc.ID(), doc)
+
+	if err = indexWriter.Batch(batch); err != nil {
+		t.Fatal(err)
+	}
+
+	indexReader, err := indexWriter.Reader()
+	if err != nil {
+		t.Fatalf("error getting index reader: %v", err)
+	}
+
+	// numeric range query with boost 5.0
+	q := NewNumericRangeQuery(20, 30).SetField("age").SetBoost(5.0)
+	sr := NewTopNSearch(10, q)
+	res, err := indexReader.Search(context.Background(), sr)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	next, err := res.Next()
+	if err != nil {
+		t.Fatalf("error getting first hit")
+	}
+	if next == nil {
+		t.Fatalf("expected at least one hit")
+	}
+	if next.Score != 5.0 {
+		t.Fatalf("expected score to be 5.0, got %f", next.Score)
+	}
+
+	err = indexReader.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = indexWriter.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestBooleanSearchBoost(t *testing.T) {
+	tmpIndexPath := createTmpIndexPath(t)
+	defer cleanupTmpIndexPath(t, tmpIndexPath)
+
+	config := DefaultConfig(tmpIndexPath)
+	indexWriter, err := OpenWriter(config)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	doc := NewDocument("doc").
+		AddField(NewNumericField("age", 25.0))
+
+	batch := NewBatch()
+	batch.Update(doc.ID(), doc)
+
+	if err = indexWriter.Batch(batch); err != nil {
+		t.Fatal(err)
+	}
+
+	indexReader, err := indexWriter.Reader()
+	if err != nil {
+		t.Fatalf("error getting index reader: %v", err)
+	}
+
+	// numeric range query with no boost
+	nrq := NewNumericRangeQuery(20, 30).SetField("age")
+	bq := NewBooleanQuery().AddMust(nrq).SetBoost(3.0)
+	sr := NewTopNSearch(10, bq)
+	res, err := indexReader.Search(context.Background(), sr)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	next, err := res.Next()
+	if err != nil {
+		t.Fatalf("error getting first hit")
+	}
+	if next == nil {
+		t.Fatalf("expected at least one hit")
+	}
+	if next.Score != 3.0 {
+		t.Fatalf("expected score to be 3.0, got %f", next.Score)
+	}
+
+	err = indexReader.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = indexWriter.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+}