fix(storage): Fix panic when read request results in empty an group

Moves the check to determine if a series has data for the current time
range into the groupBySort function, which is consistent with the
groupNoneSort function.

storage/reads/group_resultset.go

@@ -205,8 +205,8 @@ func groupNoneSort(g *groupResultSet) (int, error) {
 	n := 0
 	row := cur.Next()
 	for row != nil {
-		n++
 		if allTime || g.seriesHasPoints(row) {
+			n++
 			g.km.mergeTagKeys(row.Tags)
 		}
 		row = cur.Next()
@@ -217,22 +217,16 @@ func groupNoneSort(g *groupResultSet) (int, error) {
 }
 
 func groupByNextGroup(g *groupResultSet) GroupCursor {
-next:
 	row := g.rows[g.i]
 	for i := range g.keys {
 		g.rgc.vals[i] = row.Tags.Get(g.keys[i])
 	}
 
 	g.km.clear()
-	allTime := g.req.Hints.HintSchemaAllTime()
-	c := 0
 	rowKey := row.SortKey
 	j := g.i
 	for j < len(g.rows) && bytes.Equal(rowKey, g.rows[j].SortKey) {
-		if allTime || g.seriesHasPoints(g.rows[j]) {
-			g.km.mergeTagKeys(g.rows[j].Tags)
-			c++
-		}
+		g.km.mergeTagKeys(g.rows[j].Tags)
 		j++
 	}
 
@@ -242,9 +236,6 @@ next:
 	g.i = j
 	if j == len(g.rows) {
 		g.eof = true
-	} else if c == 0 {
-		// no rows with points
-		goto next
 	}
 
 	return &g.rgc
@@ -261,28 +252,31 @@ func groupBySort(g *groupResultSet) (int, error) {
 	var rows []*SeriesRow
 	vals := make([][]byte, len(g.keys))
 	tagsBuf := &tagsBuffer{sz: 4096}
+	allTime := g.req.Hints.HintSchemaAllTime()
 
 	row := cur.Next()
 	for row != nil {
-		nr := *row
-		nr.SeriesTags = tagsBuf.copyTags(nr.SeriesTags)
-		nr.Tags = tagsBuf.copyTags(nr.Tags)
+		if allTime || g.seriesHasPoints(row) {
+			nr := *row
+			nr.SeriesTags = tagsBuf.copyTags(nr.SeriesTags)
+			nr.Tags = tagsBuf.copyTags(nr.Tags)
 
-		l := 0
-		for i, k := range g.keys {
-			vals[i] = nr.Tags.Get(k)
-			if len(vals[i]) == 0 {
-				vals[i] = g.nilSort
+			l := 0
+			for i, k := range g.keys {
+				vals[i] = nr.Tags.Get(k)
+				if len(vals[i]) == 0 {
+					vals[i] = g.nilSort
+				}
+				l += len(vals[i])
 			}
-			l += len(vals[i])
-		}
 
-		nr.SortKey = make([]byte, 0, l)
-		for _, v := range vals {
-			nr.SortKey = append(nr.SortKey, v...)
-		}
+			nr.SortKey = make([]byte, 0, l)
+			for _, v := range vals {
+				nr.SortKey = append(nr.SortKey, v...)
+			}
 
-		rows = append(rows, &nr)
+			rows = append(rows, &nr)
+		}
 		row = cur.Next()
 	}