From e555469ba1f718498eb1a816772d22bdb1adbeac Mon Sep 17 00:00:00 2001
From: Ganesh Vernekar <ganeshvern@gmail.com>
Date: Wed, 28 Dec 2022 14:31:55 +0530
Subject: [PATCH] tsdb: Remove isHistogramSeries from memSeries

Signed-off-by: Ganesh Vernekar <ganeshvern@gmail.com>
---
 tsdb/head.go        |  4 ----
 tsdb/head_append.go | 15 ++++++++++-----
 tsdb/head_wal.go    |  2 --
 3 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/tsdb/head.go b/tsdb/head.go
index 37e12d8a4..8ec8a010d 100644
--- a/tsdb/head.go
+++ b/tsdb/head.go
@@ -1862,10 +1862,6 @@ type memSeries struct {
 	// txs is nil if isolation is disabled.
 	txs *txRing
 
-	// TODO(beorn7): The only reason we track this is to create a staleness
-	// marker as either histogram or float sample. Perhaps there is a better way.
-	isHistogramSeries bool
-
 	pendingCommit bool // Whether there are samples waiting to be committed to this series.
 }
 
diff --git a/tsdb/head_append.go b/tsdb/head_append.go
index e541f013f..72a57af3c 100644
--- a/tsdb/head_append.go
+++ b/tsdb/head_append.go
@@ -350,7 +350,7 @@ func (a *headAppender) Append(ref storage.SeriesRef, lset labels.Labels, t int64
 		}
 	}
 
-	if value.IsStaleNaN(v) && s.isHistogramSeries {
+	if value.IsStaleNaN(v) && s.lastHistogramValue != nil {
 		// TODO(marctc): do we have do to the same for float histograms?
 		return a.AppendHistogram(ref, lset, t, &histogram.Histogram{Sum: v}, nil)
 	}
@@ -555,8 +555,12 @@ func (a *headAppender) AppendHistogram(ref storage.SeriesRef, lset labels.Labels
 		if err != nil {
 			return 0, err
 		}
-		s.isHistogramSeries = true
 		if created {
+			if h != nil {
+				s.lastHistogramValue = &histogram.Histogram{}
+			} else if fh != nil {
+				s.lastFloatHistogramValue = &histogram.FloatHistogram{}
+			}
 			a.series = append(a.series, record.RefSeries{
 				Ref:    s.ref,
 				Labels: lset,
@@ -1115,11 +1119,12 @@ func (s *memSeries) append(t int64, v float64, appendID uint64, chunkDiskMapper
 		return sampleInOrder, chunkCreated
 	}
 	s.app.Append(t, v)
-	s.isHistogramSeries = false
 
 	c.maxTime = t
 
 	s.lastValue = v
+	s.lastHistogramValue = nil
+	s.lastFloatHistogramValue = nil
 
 	if appendID > 0 {
 		s.txs.add(appendID)
@@ -1184,11 +1189,11 @@ func (s *memSeries) appendHistogram(t int64, h *histogram.Histogram, appendID ui
 	}
 
 	s.app.AppendHistogram(t, h)
-	s.isHistogramSeries = true
 
 	c.maxTime = t
 
 	s.lastHistogramValue = h
+	s.lastFloatHistogramValue = nil
 
 	if appendID > 0 {
 		s.txs.add(appendID)
@@ -1252,11 +1257,11 @@ func (s *memSeries) appendFloatHistogram(t int64, fh *histogram.FloatHistogram,
 	}
 
 	s.app.AppendFloatHistogram(t, fh)
-	s.isHistogramSeries = true
 
 	c.maxTime = t
 
 	s.lastFloatHistogramValue = fh
+	s.lastHistogramValue = nil
 
 	if appendID > 0 {
 		s.txs.add(appendID)
diff --git a/tsdb/head_wal.go b/tsdb/head_wal.go
index df1896b25..97f2dcc14 100644
--- a/tsdb/head_wal.go
+++ b/tsdb/head_wal.go
@@ -605,7 +605,6 @@ func (wp *walSubsetProcessor) processWALSamples(h *Head, mmappedChunks, oooMmapp
 			if s.T <= ms.mmMaxTime {
 				continue
 			}
-			ms.isHistogramSeries = false
 			if s.T <= ms.mmMaxTime {
 				continue
 			}
@@ -634,7 +633,6 @@ func (wp *walSubsetProcessor) processWALSamples(h *Head, mmappedChunks, oooMmapp
 				unknownHistogramRefs++
 				continue
 			}
-			ms.isHistogramSeries = true
 			if s.t <= ms.mmMaxTime {
 				continue
 			}