Fix race on Cache entry

tsdb/engine/tsm1/cache.go

@@ -8,6 +8,7 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/influxdata/influxdb/influxql"
 	"github.com/influxdata/influxdb/models"
 	"github.com/influxdata/influxdb/tsdb"
 	"github.com/uber-go/zap"
@@ -147,6 +148,13 @@ func (e *entry) size() int {
 	return sz
 }
 
+// InfluxQLType returns for the entry the data type of its values.
+func (e *entry) InfluxQLType() (influxql.DataType, error) {
+	e.mu.RLock()
+	defer e.mu.RUnlock()
+	return e.values.InfluxQLType()
+}
+
 // Statistics gathered by the Cache.
 const (
 	// levels - point in time measures

tsdb/engine/tsm1/engine.go

@@ -1331,7 +1331,7 @@ func (e *Engine) onFileStoreReplace(newFiles []TSMFile) {
 
 	// load metadata from the Cache
 	e.Cache.ApplyEntryFn(func(key []byte, entry *entry) error {
-		fieldType, err := entry.values.InfluxQLType()
+		fieldType, err := entry.InfluxQLType()
 		if err != nil {
 			e.logger.Error(fmt.Sprintf("refresh index (3): %v", err))
 			return nil