fix: Add locking during tsi iterator creation.

This commit fixes a locking issue that caused the `TestShard_WritePoints_FieldConflictConcurrent`
test to fail.

tsdb/index/tsi1/log_file.go

@@ -368,7 +368,7 @@ func (f *LogFile) TagKeyIterator(name []byte) TagKeyIterator {
 	for _, k := range mm.tagSet {
 		a = append(a, k)
 	}
-	return newLogTagKeyIterator(a)
+	return newLogTagKeyIterator(f, a)
 }
 
 // TagKey returns a tag key element.
@@ -766,6 +766,7 @@ func (f *LogFile) createMeasurementIfNotExists(name []byte) *logMeasurement {
 	mm := f.mms[string(name)]
 	if mm == nil {
 		mm = &logMeasurement{
+			f:      f,
 			name:   name,
 			tagSet: make(map[string]logTagKey),
 			series: make(map[uint64]struct{}),
@@ -1204,6 +1205,7 @@ func (mms *logMeasurements) bytes() int {
 }
 
 type logMeasurement struct {
+	f         *LogFile
 	name      []byte
 	tagSet    map[string]logTagKey
 	deleted   bool
@@ -1304,7 +1306,7 @@ func (m *logMeasurement) Deleted() bool { return m.deleted }
 func (m *logMeasurement) createTagSetIfNotExists(key []byte) logTagKey {
 	ts, ok := m.tagSet[string(key)]
 	if !ok {
-		ts = logTagKey{name: key, tagValues: make(map[string]logTagValue)}
+		ts = logTagKey{f: m.f, name: key, tagValues: make(map[string]logTagValue)}
 	}
 	return ts
 }
@@ -1341,6 +1343,7 @@ func (itr *logMeasurementIterator) Next() (e MeasurementElem) {
 }
 
 type logTagKey struct {
+	f         *LogFile
 	name      []byte
 	deleted   bool
 	tagValues map[string]logTagValue
@@ -1362,10 +1365,13 @@ func (tk *logTagKey) Key() []byte   { return tk.name }
 func (tk *logTagKey) Deleted() bool { return tk.deleted }
 
 func (tk *logTagKey) TagValueIterator() TagValueIterator {
+	tk.f.mu.RLock()
 	a := make([]logTagValue, 0, len(tk.tagValues))
 	for _, v := range tk.tagValues {
 		a = append(a, v)
 	}
+	tk.f.mu.RUnlock()
+
 	return newLogTagValueIterator(a)
 }
 
@@ -1459,13 +1465,14 @@ func (a logTagValueSlice) Less(i, j int) bool { return bytes.Compare(a[i].name,
 
 // logTagKeyIterator represents an iterator over a slice of tag keys.
 type logTagKeyIterator struct {
+	f *LogFile
 	a []logTagKey
 }
 
 // newLogTagKeyIterator returns a new instance of logTagKeyIterator.
-func newLogTagKeyIterator(a []logTagKey) *logTagKeyIterator {
+func newLogTagKeyIterator(f *LogFile, a []logTagKey) *logTagKeyIterator {
 	sort.Sort(logTagKeySlice(a))
-	return &logTagKeyIterator{a: a}
+	return &logTagKeyIterator{f: f, a: a}
 }
 
 // Next returns the next element in the iterator.