GODRIVER-2734 Benchmark and reduce allocations in bson.Raw.String (#1160)

Author: matthewdale

bson/raw_test.go

@@ -11,6 +11,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"io"
+	"strings"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -345,3 +346,80 @@ func TestRaw(t *testing.T) {
 		}
 	})
 }
+
+func BenchmarkRawString(b *testing.B) {
+	// Create 1KiB and 128B strings to exercise the string-heavy call paths in
+	// the "Raw.String" method.
+	var buf strings.Builder
+	for i := 0; i < 128; i++ {
+		buf.WriteString("abcdefgh")
+	}
+	str1k := buf.String()
+	str128 := str1k[:128]
+
+	cases := []struct {
+		description string
+		value       interface{}
+	}{
+		{
+			description: "string",
+			value:       D{{Key: "key", Value: str128}},
+		},
+		{
+			description: "integer",
+			value:       D{{Key: "key", Value: int64(1234567890)}},
+		},
+		{
+			description: "float",
+			value:       D{{Key: "key", Value: float64(1234567890.123456789)}},
+		},
+		{
+			description: "nested document",
+			value: D{{
+				Key: "key",
+				Value: D{{
+					Key: "key",
+					Value: D{{
+						Key:   "key",
+						Value: str128,
+					}},
+				}},
+			}},
+		},
+		{
+			description: "array of strings",
+			value: D{{
+				Key:   "key",
+				Value: []string{str128, str128, str128, str128},
+			}},
+		},
+		{
+			description: "mixed struct",
+			value: struct {
+				Key1 struct {
+					Nested string
+				}
+				Key2 string
+				Key3 int64
+				Key4 float64
+			}{
+				Key1: struct{ Nested string }{Nested: str1k},
+				Key2: str1k,
+				Key3: 1234567890,
+				Key4: 1234567890.123456789,
+			},
+		},
+	}
+
+	for _, tc := range cases {
+		b.Run(tc.description, func(b *testing.B) {
+			bs, err := Marshal(tc.value)
+			require.NoError(b, err)
+
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				_ = Raw(bs).String()
+			}
+		})
+	}
+}

x/bsonx/bsoncore/array.go

@@ -7,10 +7,10 @@
 package bsoncore
 
 import (
-	"bytes"
 	"fmt"
 	"io"
 	"strconv"
+	"strings"
 )
 
 // NewArrayLengthError creates and returns an error for when the length of an array exceeds the
@@ -53,7 +53,7 @@ func (a Array) DebugString() string {
 	if len(a) < 5 {
 		return "<malformed>"
 	}
-	var buf bytes.Buffer
+	var buf strings.Builder
 	buf.WriteString("Array")
 	length, rem, _ := ReadLength(a) // We know we have enough bytes to read the length
 	buf.WriteByte('(')
@@ -69,7 +69,7 @@ func (a Array) DebugString() string {
 			buf.WriteString(fmt.Sprintf("<malformed (%d)>", length))
 			break
 		}
-		fmt.Fprintf(&buf, "%s", elem.Value().DebugString())
+		buf.WriteString(elem.Value().DebugString())
 		if length != 1 {
 			buf.WriteByte(',')
 		}
@@ -85,7 +85,7 @@ func (a Array) String() string {
 	if len(a) < 5 {
 		return ""
 	}
-	var buf bytes.Buffer
+	var buf strings.Builder
 	buf.WriteByte('[')
 
 	length, rem, _ := ReadLength(a) // We know we have enough bytes to read the length
@@ -100,7 +100,7 @@ func (a Array) String() string {
 		if !ok {
 			return ""
 		}
-		fmt.Fprintf(&buf, "%s", elem.Value().String())
+		buf.WriteString(elem.Value().String())
 		if length > 1 {
 			buf.WriteByte(',')
 		}

x/bsonx/bsoncore/document.go

@@ -7,11 +7,11 @@
 package bsoncore
 
 import (
-	"bytes"
 	"errors"
 	"fmt"
 	"io"
 	"strconv"
+	"strings"
 
 	"go.mongodb.org/mongo-driver/bson/bsontype"
 )
@@ -237,7 +237,7 @@ func (d Document) DebugString() string {
 	if len(d) < 5 {
 		return "<malformed>"
 	}
-	var buf bytes.Buffer
+	var buf strings.Builder
 	buf.WriteString("Document")
 	length, rem, _ := ReadLength(d) // We know we have enough bytes to read the length
 	buf.WriteByte('(')
@@ -253,7 +253,7 @@ func (d Document) DebugString() string {
 			buf.WriteString(fmt.Sprintf("<malformed (%d)>", length))
 			break
 		}
-		fmt.Fprintf(&buf, "%s ", elem.DebugString())
+		buf.WriteString(elem.DebugString())
 	}
 	buf.WriteByte('}')
 
@@ -266,7 +266,7 @@ func (d Document) String() string {
 	if len(d) < 5 {
 		return ""
 	}
-	var buf bytes.Buffer
+	var buf strings.Builder
 	buf.WriteByte('{')
 
 	length, rem, _ := ReadLength(d) // We know we have enough bytes to read the length
@@ -285,7 +285,7 @@ func (d Document) String() string {
 		if !ok {
 			return ""
 		}
-		fmt.Fprintf(&buf, "%s", elem.String())
+		buf.WriteString(elem.String())
 		first = false
 	}
 	buf.WriteByte('}')

x/bsonx/bsoncore/element.go

@@ -129,7 +129,7 @@ func (e Element) String() string {
 	if !valid {
 		return ""
 	}
-	return fmt.Sprintf(`"%s": %v`, key, val)
+	return "\"" + string(key) + "\": " + val.String()
 }
 
 // DebugString outputs a human readable version of RawElement. It will attempt to stringify the