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Signed-off-by: Marc Tuduri <marctc@protonmail.com>

model/histogram/float_histogram.go

@@ -338,29 +338,30 @@ func (h *FloatHistogram) Equals(h2 *FloatHistogram) bool {
 	return true
 }
 
-// Size returns the size of the whole fields histogram in bytes.
+// Size returns the total size of the FloatHistogram, which includes the size of the pointer
+// to FloatHistogram, all its fields, and all elements contained in slices.
 // NOTE: this is only valid for 64 bit architectures.
 func (fh *FloatHistogram) Size() int {
-	// Size of each slice separately
-	posSpanSize := len(fh.PositiveSpans) * 8     // 8 bytes (int32 + uint32)
-	negSpanSize := len(fh.NegativeSpans) * 8     // 8 bytes (int32 + uint32)
-	posBucketSize := len(fh.PositiveBuckets) * 8 // 8 bytes (float64)
-	negBucketSize := len(fh.NegativeBuckets) * 8 // 8 bytes (float64)
-
-	// Total size of the struct
-
-	// fh is 8 bytes
-	// fh.CounterResetHint is 1 byte
-	// fh.Schema is 4 bytes
-	// fh.ZeroThreshold is 8 bytes
-	// fh.ZeroCount is 8 bytes
-	// fh.Count is 8 bytes
-	// fh.Sum is 8 bytes
-	// fh.PositiveSpans is 24 bytes
-	// fh.NegativeSpans is 24 bytes
-	// fh.PositiveBuckets is 24 bytes
-	// fh.NegativeBuckets is 24 bytes
-	structSize := 141
+	// Size of each slice separately.
+	posSpanSize := len(fh.PositiveSpans) * 8     // 8 bytes (int32 + uint32).
+	negSpanSize := len(fh.NegativeSpans) * 8     // 8 bytes (int32 + uint32).
+	posBucketSize := len(fh.PositiveBuckets) * 8 // 8 bytes (float64).
+	negBucketSize := len(fh.NegativeBuckets) * 8 // 8 bytes (float64).
+
+	// Total size of the struct.
+
+	// fh is 8 bytes.
+	// fh.CounterResetHint is 4 bytes (1 byte bool + 3 bytes padding).
+	// fh.Schema is 4 bytes.
+	// fh.ZeroThreshold is 8 bytes.
+	// fh.ZeroCount is 8 bytes.
+	// fh.Count is 8 bytes.
+	// fh.Sum is 8 bytes.
+	// fh.PositiveSpans is 24 bytes.
+	// fh.NegativeSpans is 24 bytes.
+	// fh.PositiveBuckets is 24 bytes.
+	// fh.NegativeBuckets is 24 bytes.
+	structSize := 144
 
 	return structSize + posSpanSize + negSpanSize + posBucketSize + negBucketSize
 }

model/histogram/float_histogram_test.go

@@ -2362,7 +2362,7 @@ func TestFloatHistogramSize(t *testing.T) {
 				NegativeSpans:    nil,         // 24 bytes
 				NegativeBuckets:  nil,         // 24 bytes
 			},
-			8 + 1 + 4 + 8 + 8 + 8 + 8 + 24 + 24 + 24 + 24,
+			8 + 4 + 4 + 8 + 8 + 8 + 8 + 24 + 24 + 24 + 24,
 		},
 		{
 			"complete struct",
@@ -2383,7 +2383,7 @@ func TestFloatHistogramSize(t *testing.T) {
 					{3, 2}}, //  2 * 4 bytes
 				NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000}, // 24 bytes + 4 * 8 bytes
 			},
-			8 + 1 + 4 + 8 + 8 + 8 + 8 + (24 + 2*4 + 2*4) + (24 + 2*4 + 2*4) + (24 + 4*8) + (24 + 4*8),
+			8 + 4 + 4 + 8 + 8 + 8 + 8 + (24 + 2*4 + 2*4) + (24 + 2*4 + 2*4) + (24 + 4*8) + (24 + 4*8),
 		},
 	}
 

promql/engine.go

@@ -1700,7 +1700,7 @@ func (ev *evaluator) eval(expr parser.Expr) (parser.Value, annotations.Annotatio
 							}
 							point := HPoint{H: h, T: ts}
 							ss.Histograms = append(ss.Histograms, point)
-							histSize := point.histogramSize()
+							histSize := point.size()
 							ev.currentSamples += histSize
 							ev.samplesStats.IncrementSamplesAtStep(step, int64(histSize))
 						}
@@ -1818,7 +1818,7 @@ func (ev *evaluator) eval(expr parser.Expr) (parser.Value, annotations.Annotatio
 						H: mat[i].Histograms[0].H,
 					}
 					mat[i].Histograms = append(mat[i].Histograms, point)
-					ev.currentSamples += point.histogramSize()
+					ev.currentSamples += point.size()
 				}
 				if ev.currentSamples > ev.maxSamples {
 					ev.error(ErrTooManySamples(env))
@@ -2091,7 +2091,7 @@ loop:
 					histograms = getHPointSlice(16)
 				}
 				histograms = append(histograms, point)
-				ev.currentSamples += point.histogramSize()
+				ev.currentSamples += point.size()
 			}
 		case chunkenc.ValFloat:
 			t, f := buf.At()
@@ -2124,7 +2124,7 @@ loop:
 			}
 			point := HPoint{T: t, H: h}
 			histograms = append(histograms, point)
-			ev.currentSamples += point.histogramSize()
+			ev.currentSamples += point.size()
 		}
 	case chunkenc.ValFloat:
 		t, f := it.At()

promql/value.go

@@ -168,11 +168,11 @@ func (p HPoint) MarshalJSON() ([]byte, error) {
 	return json.Marshal([...]interface{}{float64(p.T) / 1000, h})
 }
 
-// histogramSize returns the size of the HPoint compared to the size of an FPoint.
+// size returns the size of the HPoint compared to the size of an FPoint.
 // The total size is calculated considering the histogram timestamp (p.T - 8 bytes),
 // and then a number of bytes in the histogram.
 // This sum is divided by 16, as samples are 16 bytes.
-func (p HPoint) histogramSize() int {
+func (p HPoint) size() int {
 	return (p.H.Size() + 8) / 16
 }
 
@@ -180,7 +180,7 @@ func (p HPoint) histogramSize() int {
 func totalHPointSize(histograms []HPoint) int {
 	var total int
 	for _, h := range histograms {
-		total += h.histogramSize()
+		total += h.size()
 	}
 	return total
 }
@@ -246,7 +246,7 @@ func (vec Vector) String() string {
 // TotalSamples returns the total number of samples in the series within a vector.
 // Float samples have a weight of 1 in this number, while histogram samples have a higher
 // weight according to their size compared with the size of a float sample.
-// See HPoint.histogramSize for details.
+// See HPoint.size for details.
 func (vec Vector) TotalSamples() int {
 	numSamples := 0
 	for _, sample := range vec {
@@ -296,7 +296,9 @@ func (m Matrix) String() string {
 }
 
 // TotalSamples returns the total number of samples in the series within a matrix.
-// It takes into account the number of samples in the histograms using the histogramSize method.
+// Float samples have a weight of 1 in this number, while histogram samples have a higher
+// weight according to their size compared with the size of a float sample.
+// See HPoint.size for details.
 func (m Matrix) TotalSamples() int {
 	numSamples := 0
 	for _, series := range m {