Support float histogram in store gateway

CHANGELOG.md

@@ -18,6 +18,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 
 - [#6891](https://github.com/thanos-io/thanos/pull/6891) Objstore: Bump `objstore` which adds support for Azure Workload Identity.
 - [#6453](https://github.com/thanos-io/thanos/pull/6453) Sidecar: Added `--reloader.method` to support configuration reloads via SIHUP signal.
+- [#6925](https://github.com/thanos-io/thanos/pull/6925) Store Gateway: Support float native histogram.
 
 ### Changed
 

pkg/store/bucket.go

@@ -1251,7 +1251,7 @@ func populateChunk(out *storepb.AggrChunk, in chunkenc.Chunk, aggrs []storepb.Ag
 	hasher := hashPool.Get().(hash.Hash64)
 	defer hashPool.Put(hasher)
 
-	if in.Encoding() == chunkenc.EncXOR || in.Encoding() == chunkenc.EncHistogram {
+	if in.Encoding() == chunkenc.EncXOR || in.Encoding() == chunkenc.EncHistogram || in.Encoding() == chunkenc.EncFloatHistogram {
 		b, err := save(in.Bytes())
 		if err != nil {
 			return err

pkg/store/bucket_test.go

@@ -1301,6 +1301,13 @@ func TestBucketHistogramSeries(t *testing.T) {
 	})
 }
 
+func TestBucketFloatHistogramSeries(t *testing.T) {
+	tb := testutil.NewTB(t)
+	storetestutil.RunSeriesInterestingCases(tb, 200e3, 200e3, func(t testutil.TB, samplesPerSeries, series int) {
+		benchBucketSeries(t, chunkenc.ValFloatHistogram, false, false, samplesPerSeries, series, 1)
+	})
+}
+
 func TestBucketSkipChunksSeries(t *testing.T) {
 	tb := testutil.NewTB(t)
 	storetestutil.RunSeriesInterestingCases(tb, 200e3, 200e3, func(t testutil.TB, samplesPerSeries, series int) {

pkg/store/storepb/prompb/types.proto

@@ -172,6 +172,7 @@ message Chunk {
     UNKNOWN = 0;
     XOR = 1;
     HISTOGRAM = 2;
+    FLOAT_HISTOGRAM = 3;
   }
   Encoding type = 3;
   bytes data = 4;

pkg/store/storepb/testutil/series.go

@@ -120,6 +120,8 @@ func CreateHeadWithSeries(t testing.TB, j int, opts HeadGenOptions) (*tsdb.Head,
 			appendFloatSamples(t, app, tsLabel, opts)
 		case chunkenc.ValHistogram:
 			appendHistogramSamples(t, app, tsLabel, opts)
+		case chunkenc.ValFloatHistogram:
+			appendFloatHistogramSamples(t, app, tsLabel, opts)
 		}
 	}
 	testutil.Ok(t, app.Commit())
@@ -222,6 +224,39 @@ func appendHistogramSamples(t testing.TB, app storage.Appender, tsLabel int, opt
 	}
 }
 
+func appendFloatHistogramSamples(t testing.TB, app storage.Appender, tsLabel int, opts HeadGenOptions) {
+	sample := &histogram.FloatHistogram{
+		ZeroThreshold: 0.01,
+		ZeroCount:     5.5,
+		Count:         15,
+		Sum:           11.5,
+		PositiveSpans: []histogram.Span{
+			{Offset: -2, Length: 2},
+			{Offset: 1, Length: 3},
+		},
+		PositiveBuckets: []float64{0.5, 0, 1.5, 2, 3.5},
+		NegativeSpans: []histogram.Span{
+			{Offset: 3, Length: 2},
+			{Offset: 3, Length: 2},
+		},
+		NegativeBuckets: []float64{1.5, 0.5, 2.5, 3},
+	}
+
+	ref, err := app.AppendHistogram(
+		0,
+		labels.FromStrings("foo", "bar", "i", fmt.Sprintf("%07d%s", tsLabel, LabelLongSuffix), "j", fmt.Sprintf("%v", tsLabel)),
+		int64(tsLabel)*opts.ScrapeInterval.Milliseconds(),
+		nil,
+		sample,
+	)
+	testutil.Ok(t, err)
+
+	for is := 1; is < opts.SamplesPerSeries; is++ {
+		_, err := app.AppendHistogram(ref, labels.EmptyLabels(), int64(tsLabel+is)*opts.ScrapeInterval.Milliseconds(), nil, sample)
+		testutil.Ok(t, err)
+	}
+}
+
 // SeriesServer is test gRPC storeAPI series server.
 type SeriesServer struct {
 	// This field just exist to pseudo-implement the unused methods of the interface.