From eb9a542c1f4d489d6ac392847cd0a86e4b30b27f Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@victoriametrics.com>
Date: Sat, 7 Jan 2023 01:04:41 -0800
Subject: [PATCH] lib/storage: simplify the fix from
 488940502c55b8ed0e693daf097a8eb96e2af70f

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3566
---
 lib/storage/index_db.go | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/lib/storage/index_db.go b/lib/storage/index_db.go
index 5b322eb61a..7a648cce1a 100644
--- a/lib/storage/index_db.go
+++ b/lib/storage/index_db.go
@@ -852,6 +852,7 @@ func (is *indexSearch) searchLabelNamesWithFiltersOnDate(qt *querytracer.Tracer,
 	mp := &is.mp
 	dmis := is.db.s.getDeletedMetricIDs()
 	loopsPaceLimiter := 0
+	underscoreNameSeen := false
 	nsPrefixExpected := byte(nsPrefixDateTagToMetricIDs)
 	if date == 0 {
 		nsPrefixExpected = nsPrefixTagToMetricIDs
@@ -878,9 +879,9 @@ func (is *indexSearch) searchLabelNamesWithFiltersOnDate(qt *querytracer.Tracer,
 		}
 		labelName := mp.Tag.Key
 		if len(labelName) == 0 {
-			labelName = []byte("__name__")
+			underscoreNameSeen = true
 		}
-		if isArtificialTagKey(labelName) {
+		if isArtificialTagKey(labelName) || string(labelName) == string(prevLabelName) {
 			// Search for the next tag key.
 			// The last char in kb.B must be tagSeparatorChar.
 			// Just increment it in order to jump to the next tag key.
@@ -895,20 +896,12 @@ func (is *indexSearch) searchLabelNamesWithFiltersOnDate(qt *querytracer.Tracer,
 			ts.Seek(kb.B)
 			continue
 		}
-		if string(labelName) == string(prevLabelName) {
-			var tagValue []byte
-			if string(labelName) != "__name__" {
-				tagValue = labelName
-			}
-			kb.B = is.marshalCommonPrefixForDate(kb.B[:0], date)
-			kb.B = marshalTagValue(kb.B, tagValue)
-			kb.B[len(kb.B)-1]++
-			ts.Seek(kb.B)
-			continue
-		}
 		lns[string(labelName)] = struct{}{}
 		prevLabelName = append(prevLabelName[:0], labelName...)
 	}
+	if underscoreNameSeen {
+		lns["__name__"] = struct{}{}
+	}
 	if err := ts.Error(); err != nil {
 		return fmt.Errorf("error during search for prefix %q: %w", prefix, err)
 	}