From 2d61d012ff7c96a12a8d1aba52d3eb19e8d2db46 Mon Sep 17 00:00:00 2001
From: "Xiaochao Dong (@damnever)" <the.xcdong@gmail.com>
Date: Fri, 30 Dec 2022 19:11:29 +0800
Subject: [PATCH] Avoid copy during remote write if external labels is empty

Signed-off-by: Xiaochao Dong (@damnever) <the.xcdong@gmail.com>
---
 storage/remote/queue_manager.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/storage/remote/queue_manager.go b/storage/remote/queue_manager.go
index f907615fc9..15634aa68d 100644
--- a/storage/remote/queue_manager.go
+++ b/storage/remote/queue_manager.go
@@ -847,6 +847,10 @@ func (t *QueueManager) releaseLabels(ls labels.Labels) {
 // processExternalLabels merges externalLabels into ls. If ls contains
 // a label in externalLabels, the value in ls wins.
 func processExternalLabels(ls labels.Labels, externalLabels []labels.Label) labels.Labels {
+	if len(externalLabels) == 0 {
+		return ls
+	}
+
 	b := labels.NewScratchBuilder(ls.Len() + len(externalLabels))
 	j := 0
 	ls.Range(func(l labels.Label) {