From 0e1ae1d1caa65c398d0024a4ecb7977405e15a07 Mon Sep 17 00:00:00 2001
From: Filip Petkovski <filip.petkovsky@gmail.com>
Date: Mon, 25 Dec 2023 11:41:07 +0100
Subject: [PATCH] Add comment

Signed-off-by: Filip Petkovski <filip.petkovsky@gmail.com>
---
 promql/engine.go | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/promql/engine.go b/promql/engine.go
index 5d6f7b9a08..2ea37dae60 100644
--- a/promql/engine.go
+++ b/promql/engine.go
@@ -2136,6 +2136,8 @@ loop:
 				if histograms == nil {
 					histograms = getHPointSlice(16)
 				}
+				// The last sample comes directly from the iterator, so we need to copy it to
+				// avoid having the same reference twice in the buffer.
 				point := HPoint{T: t, H: h.Copy()}
 				histograms = append(histograms, point)
 				ev.currentSamples += point.size()