Add ldcontext.NewBuilderWithCapacity constructor

internal/sharedtest/custom_attributes.go

@@ -7,8 +7,9 @@ import (
 )
 
 const (
-	SmallNumberOfCustomAttributes = 2  //nolint:revive
-	LargeNumberOfCustomAttributes = 20 //nolint:revive
+	SmallNumberOfCustomAttributes  = 2  //nolint:revive
+	MiddleNumberOfCustomAttributes = 10 //nolint:revive
+	LargeNumberOfCustomAttributes  = 50
 )
 
 type NameAndLDValue struct { //nolint:revive

ldcontext/builder_benchmark_test.go

@@ -31,7 +31,11 @@ func BenchmarkBuildWithNoCustomAttrs(b *testing.B) {
 }
 
 func BenchmarkBuildWithCustomAttributes(b *testing.B) {
-	for _, n := range []int{sharedtest.SmallNumberOfCustomAttributes, sharedtest.LargeNumberOfCustomAttributes} {
+	for _, n := range []int{
+		sharedtest.SmallNumberOfCustomAttributes,
+		sharedtest.MiddleNumberOfCustomAttributes,
+		sharedtest.LargeNumberOfCustomAttributes,
+	} {
 		b.Run(fmt.Sprintf("with %d attributes", n), func(b *testing.B) {
 			attrs := sharedtest.MakeCustomAttributeNamesAndValues(n)
 			b.ResetTimer()
@@ -46,6 +50,26 @@ func BenchmarkBuildWithCustomAttributes(b *testing.B) {
 	}
 }
 
+func BenchmarkBuildWithCustomAttributesWithCapacity(b *testing.B) {
+	for _, n := range []int{
+		sharedtest.SmallNumberOfCustomAttributes,
+		sharedtest.MiddleNumberOfCustomAttributes,
+		sharedtest.LargeNumberOfCustomAttributes,
+	} {
+		b.Run(fmt.Sprintf("with %d attributes", n), func(b *testing.B) {
+			attrs := sharedtest.MakeCustomAttributeNamesAndValues(n)
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				builder := NewBuilderWithCapacity("key", n)
+				for _, a := range attrs {
+					builder.SetValue(a.Name, a.Value)
+				}
+				benchmarkContext = builder.Build()
+			}
+		})
+	}
+}
+
 func BenchmarkBuildWithPrivate(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		benchmarkContext = NewBuilder("key").Name("name").Private("name").Build()

ldcontext/builder_simple.go

@@ -126,6 +126,14 @@ func NewBuilder(key string) *Builder {
 	return b.Key(key)
 }
 
+// NewBuilderWithCapacity extends the behavior of NewBuilder to pre-allocate capacity for attributes.
+func NewBuilderWithCapacity(key string, capacity int) *Builder {
+	b := &Builder{
+		attributes: *ldvalue.ValueMapBuildWithCapacity(capacity),
+	}
+	return b.Key(key)
+}
+
 // NewBuilderFromContext creates a Builder whose properties are the same as an existing
 // single context.
 //