refactor(tsdb): remove read from unexported field (#17279)

* refactor(tsdb): remove read from unexported field

* fix(tsdb): add regression test to check for panic

* fix(tsdb): detect nil without panic

tsdb/series_iterators.go

@@ -30,7 +30,7 @@ type seriesIDSetIterator struct {
 }
 
 func NewSeriesIDSetIterator(ss *SeriesIDSet) SeriesIDSetIterator {
-	if ss == nil || ss.bitmap == nil {
+	if ss == nil || ss.IsEmpty() {
 		return nil
 	}
 	return &seriesIDSetIterator{ss: ss, itr: ss.Iterator()}

tsdb/series_iterators_test.go

@@ -18,6 +18,7 @@ import (
 	"github.com/influxdata/influxdb/tsdb/seriesfile"
 	"github.com/influxdata/influxdb/tsdb/tsi1"
 	"github.com/influxdata/influxql"
+	"github.com/stretchr/testify/assert"
 )
 
 func toSeriesIDs(ids []uint64) []tsdb.SeriesID {
@@ -355,3 +356,25 @@ func BenchmarkIndex_ConcurrentWriteQuery(b *testing.B) {
 		})
 	}
 }
+
+func TestSeriesIDSet_isEmpty(t *testing.T) {
+	sis := tsdb.NewSeriesIDSet(tsdb.NewSeriesID(1))
+	assert.False(t, sis.IsEmpty())
+
+	sis = tsdb.NewSeriesIDSet()
+	assert.True(t, sis.IsEmpty())
+
+	sis = &tsdb.SeriesIDSet{} // sis.bitmap == nil
+	assert.True(t, sis.IsEmpty())
+}
+
+func TestNewSeriesIDSetIterator(t *testing.T) {
+	sisi := tsdb.NewSeriesIDSetIterator(tsdb.NewSeriesIDSet(tsdb.NewSeriesID(1)))
+	assert.NotNil(t, sisi)
+
+	sisi = tsdb.NewSeriesIDSetIterator(tsdb.NewSeriesIDSet())
+	assert.Nil(t, sisi)
+
+	sisi = tsdb.NewSeriesIDSetIterator(nil)
+	assert.Nil(t, sisi)
+}

tsdb/series_set.go

@@ -48,6 +48,10 @@ func (s *SeriesIDSet) Bytes() int {
 	return b
 }
 
+func (s *SeriesIDSet) IsEmpty() bool {
+	return s == nil || s.bitmap == nil || s.bitmap.IsEmpty()
+}
+
 // Add adds the series id to the set.
 func (s *SeriesIDSet) Add(id SeriesID) {
 	s.Lock()