From 3127aa92b5faca403f27ae2163ba41e8ba931213 Mon Sep 17 00:00:00 2001
From: n4mine <n4mine@foxmail.com>
Date: Fri, 6 Nov 2020 07:29:24 +0800
Subject: [PATCH] app/vmselect/promql: fix when the parameter of `maxValue()`,
 `minValue()` leading by `NaN`. it will cause `{top,bottom}k_{max,min}` return
 inappropriate result (#883)

---
 app/vmselect/promql/aggr.go | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/app/vmselect/promql/aggr.go b/app/vmselect/promql/aggr.go
index 050a8cbd48..f30313df7d 100644
--- a/app/vmselect/promql/aggr.go
+++ b/app/vmselect/promql/aggr.go
@@ -740,12 +740,21 @@ func minValue(values []float64) float64 {
 	if len(values) == 0 {
 		return nan
 	}
-	min := values[0]
-	for _, v := range values[1:] {
-		if v < min {
+	aNumberFounded := false
+	var min float64
+	for _, v := range values {
+		if !math.IsNaN(v) && !aNumberFounded {
+			min = v
+			aNumberFounded = true
+			continue
+		}
+		if !math.IsNaN(v) && v < min {
 			min = v
 		}
 	}
+	if !aNumberFounded {
+		return nan
+	}
 	return min
 }
 
@@ -753,12 +762,21 @@ func maxValue(values []float64) float64 {
 	if len(values) == 0 {
 		return nan
 	}
-	max := values[0]
-	for _, v := range values[1:] {
-		if v > max {
+	aNumberFounded := false
+	var max float64
+	for _, v := range values {
+		if !math.IsNaN(v) && !aNumberFounded {
+			max = v
+			aNumberFounded = true
+			continue
+		}
+		if !math.IsNaN(v) && v > max {
 			max = v
 		}
 	}
+	if !aNumberFounded {
+		return nan
+	}
 	return max
 }