From 52eb303031450f06e4d2da6c3f08681c0a5b8bb3 Mon Sep 17 00:00:00 2001
From: Jeanette Tan <jeanette.tan@grafana.com>
Date: Thu, 2 Nov 2023 21:23:05 +0800
Subject: [PATCH] Refactor assigning MinTime in histogram chunks

Signed-off-by: Jeanette Tan <jeanette.tan@grafana.com>
---
 tsdb/querier.go | 28 +++++++---------------------
 1 file changed, 7 insertions(+), 21 deletions(-)

diff --git a/tsdb/querier.go b/tsdb/querier.go
index 9a01e8c49b..a832c0d1ba 100644
--- a/tsdb/querier.go
+++ b/tsdb/querier.go
@@ -840,6 +840,7 @@ func (p *populateWithDelChunkSeriesIterator) Next() bool {
 		}
 		return false
 	}
+	p.curr.MinTime = p.currDelIter.AtT()
 
 	// Re-encode the chunk if iterator is provider. This means that it has
 	// some samples to be deleted or chunk is opened.
@@ -855,18 +856,12 @@ func (p *populateWithDelChunkSeriesIterator) Next() bool {
 		if app, err = newChunk.Appender(); err != nil {
 			break
 		}
-		var h *histogram.Histogram
-		t, h = p.currDelIter.AtHistogram()
-		p.curr.MinTime = t
-		_, _, app, err = app.AppendHistogram(nil, t, h, true)
-		if err != nil {
-			break
-		}
-		for vt := p.currDelIter.Next(); vt != chunkenc.ValNone; vt = p.currDelIter.Next() {
+		for vt := valueType; vt != chunkenc.ValNone; vt = p.currDelIter.Next() {
 			if vt != chunkenc.ValHistogram {
 				err = fmt.Errorf("found value type %v in histogram chunk", vt)
 				break
 			}
+			var h *histogram.Histogram
 			t, h = p.currDelIter.AtHistogram()
 			_, _, app, err = app.AppendHistogram(nil, t, h, true)
 			if err != nil {
@@ -878,15 +873,12 @@ func (p *populateWithDelChunkSeriesIterator) Next() bool {
 		if app, err = newChunk.Appender(); err != nil {
 			break
 		}
-		var v float64
-		t, v = p.currDelIter.At()
-		p.curr.MinTime = t
-		app.Append(t, v)
-		for vt := p.currDelIter.Next(); vt != chunkenc.ValNone; vt = p.currDelIter.Next() {
+		for vt := valueType; vt != chunkenc.ValNone; vt = p.currDelIter.Next() {
 			if vt != chunkenc.ValFloat {
 				err = fmt.Errorf("found value type %v in float chunk", vt)
 				break
 			}
+			var v float64
 			t, v = p.currDelIter.At()
 			app.Append(t, v)
 		}
@@ -895,18 +887,12 @@ func (p *populateWithDelChunkSeriesIterator) Next() bool {
 		if app, err = newChunk.Appender(); err != nil {
 			break
 		}
-		var h *histogram.FloatHistogram
-		t, h = p.currDelIter.AtFloatHistogram()
-		p.curr.MinTime = t
-		_, _, app, err = app.AppendFloatHistogram(nil, t, h, true)
-		if err != nil {
-			break
-		}
-		for vt := p.currDelIter.Next(); vt != chunkenc.ValNone; vt = p.currDelIter.Next() {
+		for vt := valueType; vt != chunkenc.ValNone; vt = p.currDelIter.Next() {
 			if vt != chunkenc.ValFloatHistogram {
 				err = fmt.Errorf("found value type %v in histogram chunk", vt)
 				break
 			}
+			var h *histogram.FloatHistogram
 			t, h = p.currDelIter.AtFloatHistogram()
 			_, _, app, err = app.AppendFloatHistogram(nil, t, h, true)
 			if err != nil {