Create a noOpInterner in case string interning is disabled (#6705)

Signed-off-by: alanprot <[email protected]>

Author: alanprot

Diff for: pkg/ingester/ingester.go

@@ -2386,7 +2386,7 @@ func (i *Ingester) createTSDB(userID string) (*userTSDB, error) {
 
 		instanceLimitsFn:             i.getInstanceLimits,
 		instanceSeriesCount:          &i.TSDBState.seriesCount,
-		interner:                     util.NewLruInterner(),
+		interner:                     util.NewLruInterner(i.cfg.LabelsStringInterningEnabled),
 		labelsStringInterningEnabled: i.cfg.LabelsStringInterningEnabled,
 
 		blockRetentionPeriod: i.cfg.BlocksStorageConfig.TSDB.Retention.Milliseconds(),

Diff for: pkg/util/strings.go

@@ -157,12 +157,21 @@ type Interner interface {
 
 // NewLruInterner returns a new Interner to be used to intern strings.
 // The interner will use a LRU cache to return the deduplicated strings
-func NewLruInterner() Interner {
+func NewLruInterner(enabled bool) Interner {
+	if !enabled {
+		return &noOpInterner{}
+	}
 	return &pool{
 		lru: expirable.NewLRU[string, string](maxInternerLruCacheSize, nil, internerLruCacheTTL),
 	}
 }
 
+type noOpInterner struct{}
+
+func (n noOpInterner) Intern(s string) string {
+	return s
+}
+
 type pool struct {
 	lru *expirable.LRU[string, string]
 }