Merge pull request #13776 from aknuds1/arve/checkpoint-histogram-samples

tsdb/wlog.Checkpoint: Fix counting of histogram samples

tsdb/wlog/checkpoint.go

@@ -224,8 +224,8 @@ func Checkpoint(logger log.Logger, w *WL, from, to int, keep func(id chunks.Head
 			if len(repl) > 0 {
 				buf = enc.HistogramSamples(repl, buf)
 			}
-			stats.TotalSamples += len(samples)
-			stats.DroppedSamples += len(samples) - len(repl)
+			stats.TotalSamples += len(histogramSamples)
+			stats.DroppedSamples += len(histogramSamples) - len(repl)
 
 		case record.Tombstones:
 			tstones, err = dec.Tombstones(rec, tstones)

tsdb/wlog/checkpoint_test.go

@@ -220,12 +220,14 @@ func TestCheckpoint(t *testing.T) {
 			}
 			require.NoError(t, w.Close())
 
-			_, err = Checkpoint(log.NewNopLogger(), w, 100, 106, func(x chunks.HeadSeriesRef) bool {
+			stats, err := Checkpoint(log.NewNopLogger(), w, 100, 106, func(x chunks.HeadSeriesRef) bool {
 				return x%2 == 0
 			}, last/2)
 			require.NoError(t, err)
 			require.NoError(t, w.Truncate(107))
 			require.NoError(t, DeleteCheckpoints(w.Dir(), 106))
+			require.Equal(t, histogramsInWAL+samplesInWAL, stats.TotalSamples)
+			require.Greater(t, stats.DroppedSamples, 0)
 
 			// Only the new checkpoint should be left.
 			files, err := os.ReadDir(dir)