Ensure buffers passed to labels.Labels.Bytes(), BytesWithLabels() and…

… BytesWithoutLabels() are reused if resized

pkg/streamingpromql/operators/aggregations/aggregation.go

@@ -212,7 +212,8 @@ func (a *Aggregation) groupingWithoutLabelsSeriesToGroupFuncs() (seriesToGroupLa
 	// Why 1024 bytes? It's what labels.Labels.String() uses as a buffer size, so we use that as a sensible starting point too.
 	b := make([]byte, 0, 1024)
 	bytesFunc := func(l labels.Labels) []byte {
-		return l.BytesWithoutLabels(b, a.Grouping...) // NewAggregation will add __name__ to Grouping for 'without' aggregations, so no need to add it here.
+		b = l.BytesWithoutLabels(b, a.Grouping...) // NewAggregation will add __name__ to Grouping for 'without' aggregations, so no need to add it here.
+		return b
 	}
 
 	lb := labels.NewBuilder(labels.EmptyLabels())
@@ -231,7 +232,8 @@ func (a *Aggregation) groupingByLabelsSeriesToGroupFuncs() (seriesToGroupLabelsB
 	// Why 1024 bytes? It's what labels.Labels.String() uses as a buffer size, so we use that as a sensible starting point too.
 	b := make([]byte, 0, 1024)
 	bytesFunc := func(l labels.Labels) []byte {
-		return l.BytesWithLabels(b, a.Grouping...)
+		b = l.BytesWithLabels(b, a.Grouping...)
+		return b
 	}
 
 	lb := labels.NewBuilder(labels.EmptyLabels())

pkg/streamingpromql/operators/binops/binary_operation.go

@@ -29,14 +29,16 @@ func vectorMatchingGroupKeyFunc(vectorMatching parser.VectorMatching) func(label
 		slices.Sort(vectorMatching.MatchingLabels)
 
 		return func(l labels.Labels) []byte {
-			return l.BytesWithLabels(buf, vectorMatching.MatchingLabels...)
+			buf = l.BytesWithLabels(buf, vectorMatching.MatchingLabels...)
+			return buf
 		}
 	}
 
 	if len(vectorMatching.MatchingLabels) == 0 {
 		// Fast path for common case for expressions like "a + b" with no 'on' or 'without' labels.
 		return func(l labels.Labels) []byte {
-			return l.BytesWithoutLabels(buf, labels.MetricName)
+			buf = l.BytesWithoutLabels(buf, labels.MetricName)
+			return buf
 		}
 	}
 
@@ -46,7 +48,8 @@ func vectorMatchingGroupKeyFunc(vectorMatching parser.VectorMatching) func(label
 	slices.Sort(lbls)
 
 	return func(l labels.Labels) []byte {
-		return l.BytesWithoutLabels(buf, lbls...)
+		buf = l.BytesWithoutLabels(buf, lbls...)
+		return buf
 	}
 }
 

pkg/streamingpromql/operators/binops/grouped_vector_vector_binary_operation.go

@@ -387,7 +387,8 @@ func (g *GroupedVectorVectorBinaryOperation) additionalLabelsKeyFunc() func(oneS
 	buf := make([]byte, 0, 1024)
 
 	return func(oneSideLabels labels.Labels) []byte {
-		return oneSideLabels.BytesWithLabels(buf, g.VectorMatching.Include...)
+		buf = oneSideLabels.BytesWithLabels(buf, g.VectorMatching.Include...)
+		return buf
 	}
 }
 
@@ -398,13 +399,15 @@ func (g *GroupedVectorVectorBinaryOperation) manySideGroupKeyFunc() func(manySid
 
 	if !g.shouldRemoveMetricNameFromManySide() && len(g.VectorMatching.Include) == 0 {
 		return func(manySideLabels labels.Labels) []byte {
-			return manySideLabels.Bytes(buf) // FIXME: it'd be nice if we could avoid copying the bytes here
+			buf = manySideLabels.Bytes(buf) // FIXME: it'd be nice if we could avoid Bytes() copying the slice here
+			return buf
 		}
 	}
 
 	if len(g.VectorMatching.Include) == 0 {
 		return func(manySideLabels labels.Labels) []byte {
-			return manySideLabels.BytesWithoutLabels(buf, labels.MetricName)
+			buf = manySideLabels.BytesWithoutLabels(buf, labels.MetricName)
+			return buf
 		}
 	}
 
@@ -416,7 +419,8 @@ func (g *GroupedVectorVectorBinaryOperation) manySideGroupKeyFunc() func(manySid
 	}
 
 	return func(manySideLabels labels.Labels) []byte {
-		return manySideLabels.BytesWithoutLabels(buf, labelsToRemove...)
+		buf = manySideLabels.BytesWithoutLabels(buf, labelsToRemove...)
+		return buf
 	}
 }