Replace usages of bytes.Buffer with strings.Builder

I went through each of these manually and eyeballed to make sure they
followed the pattern of only creating the buffer and using the result of
.String() after later.

I didn't do everything within tests since I didn't think it was too
relevant.

I also unified some of the usage patterns to be `var buf
strings.Builder` as opposed to `buf := new(bytes.Buffer)` etc.

All of the rest of the changes were just from gofmt. I'm assuming they
are fine, but I understand this adds some more noise to the diffs and
might not be desired. I can look into teasing them out if that's a
concern.

But overall, this change should yield 1 less memory allocation since the
bytes -> string is done without an extra allocation.

Signed-off-by: Matt Robenolt <[email protected]>

go/bytes2/buffer.go

@@ -65,7 +65,7 @@ func (buf *Buffer) String() string {
 // is _not_ allocated, so modifying this buffer after calling StringUnsafe will lead
 // to undefined behavior.
 func (buf *Buffer) StringUnsafe() string {
-	return *(*string)(unsafe.Pointer(&buf.bytes))
+	return unsafe.String(unsafe.SliceData(buf.bytes), len(buf.bytes))
 }
 
 // Reset is equivalent to bytes.Buffer.Reset.

go/mysql/collations/integration/collations_test.go

@@ -59,7 +59,7 @@ func getSQLQueries(t *testing.T, testfile string) []string {
 	defer tf.Close()
 
 	var chunks []string
-	var curchunk bytes.Buffer
+	var curchunk strings.Builder
 
 	addchunk := func() {
 		if curchunk.Len() > 0 {
@@ -219,8 +219,8 @@ func TestCollationsOnMysqld(t *testing.T) {
 }
 
 func TestRemoteKanaSensitivity(t *testing.T) {
-	var Kana1 = []byte("の東京ノ")
-	var Kana2 = []byte("ノ東京の")
+	Kana1 := []byte("の東京ノ")
+	Kana2 := []byte("ノ東京の")
 
 	testRemoteComparison(t, nil, []testcmp{
 		{"utf8mb4_0900_as_cs", Kana1, Kana2},

go/mysql/sqlerror/sql_error.go

@@ -17,7 +17,6 @@ limitations under the License.
 package sqlerror
 
 import (
-	"bytes"
 	"fmt"
 	"regexp"
 	"strconv"
@@ -53,17 +52,17 @@ func NewSQLError(number ErrorCode, sqlState string, format string, args ...any)
 
 // Error implements the error interface
 func (se *SQLError) Error() string {
-	buf := &bytes.Buffer{}
+	var buf strings.Builder
 	buf.WriteString(se.Message)
 
 	// Add MySQL errno and SQLSTATE in a format that we can later parse.
 	// There's no avoiding string parsing because all errors
 	// are converted to strings anyway at RPC boundaries.
 	// See NewSQLErrorFromError.
-	fmt.Fprintf(buf, " (errno %v) (sqlstate %v)", se.Num, se.State)
+	fmt.Fprintf(&buf, " (errno %v) (sqlstate %v)", se.Num, se.State)
 
 	if se.Query != "" {
-		fmt.Fprintf(buf, " during query: %s", sqlparser.TruncateForLog(se.Query))
+		fmt.Fprintf(&buf, " during query: %s", sqlparser.TruncateForLog(se.Query))
 	}
 
 	return buf.String()

go/sqltypes/bind_variables.go

@@ -17,10 +17,10 @@ limitations under the License.
 package sqltypes
 
 import (
-	"bytes"
 	"errors"
 	"fmt"
 	"strconv"
+	"strings"
 
 	"google.golang.org/protobuf/proto"
 
@@ -418,7 +418,7 @@ func FormatBindVariables(bindVariables map[string]*querypb.BindVariable, full, a
 	}
 
 	if asJSON {
-		var buf bytes.Buffer
+		var buf strings.Builder
 		buf.WriteString("{")
 		first := true
 		for k, v := range out {

go/sqltypes/testing.go

@@ -17,7 +17,6 @@ limitations under the License.
 package sqltypes
 
 import (
-	"bytes"
 	crand "crypto/rand"
 	"encoding/base64"
 	"encoding/hex"
@@ -155,13 +154,13 @@ func TestTuple(vals ...Value) Value {
 // PrintResults prints []*Results into a string.
 // This function should only be used for testing.
 func PrintResults(results []*Result) string {
-	b := new(bytes.Buffer)
+	var b strings.Builder
 	for i, r := range results {
 		if i == 0 {
-			fmt.Fprintf(b, "%v", r)
+			fmt.Fprintf(&b, "%v", r)
 			continue
 		}
-		fmt.Fprintf(b, ", %v", r)
+		fmt.Fprintf(&b, ", %v", r)
 	}
 	return b.String()
 }

go/sqltypes/value_test.go

@@ -463,13 +463,13 @@ func TestEncode(t *testing.T) {
 		outASCII: "'YQ=='",
 	}}
 	for _, tcase := range testcases {
-		buf := &bytes.Buffer{}
-		tcase.in.EncodeSQL(buf)
+		var buf strings.Builder
+		tcase.in.EncodeSQL(&buf)
 		if tcase.outSQL != buf.String() {
 			t.Errorf("%v.EncodeSQL = %q, want %q", tcase.in, buf.String(), tcase.outSQL)
 		}
-		buf = &bytes.Buffer{}
-		tcase.in.EncodeASCII(buf)
+		buf.Reset()
+		tcase.in.EncodeASCII(&buf)
 		if tcase.outASCII != buf.String() {
 			t.Errorf("%v.EncodeASCII = %q, want %q", tcase.in, buf.String(), tcase.outASCII)
 		}

go/stats/opentsdb/collector.go

@@ -17,7 +17,6 @@ limitations under the License.
 package opentsdb
 
 import (
-	"bytes"
 	"encoding/json"
 	"expvar"
 	"strings"
@@ -65,7 +64,7 @@ func (dc *collector) addFloat(metric string, val float64, tags map[string]string
 	// Also make everything lowercase, since opentsdb is case sensitive and lowercase
 	// simplifies the convention.
 	sanitize := func(text string) string {
-		var b bytes.Buffer
+		var b strings.Builder
 		for _, r := range text {
 			if unicode.IsDigit(r) || unicode.IsLetter(r) || r == '-' || r == '_' || r == '/' || r == '.' {
 				b.WriteRune(r)

go/tools/release-notes/release_notes.go

@@ -17,7 +17,6 @@ limitations under the License.
 package main
 
 import (
-	"bytes"
 	"encoding/json"
 	"fmt"
 	"log"
@@ -79,9 +78,7 @@ type (
 	}
 )
 
-var (
-	releaseNotesPath = `changelog/`
-)
+var releaseNotesPath = `changelog/`
 
 const (
 	releaseNotesPathGitHub = `https://github.com/vitessio/vitess/blob/main/`
@@ -141,7 +138,7 @@ func (rn *releaseNote) generate(rnFile, changelogFile *os.File) error {
 	// Generate the release notes
 	rn.PathToChangeLogFileOnGH = releaseNotesPathGitHub + path.Join(rn.SubDirPath, "changelog.md")
 	if rnFile == nil {
-		rnFile, err = os.OpenFile(path.Join(rn.SubDirPath, "release_notes.md"), os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
+		rnFile, err = os.OpenFile(path.Join(rn.SubDirPath, "release_notes.md"), os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0o666)
 		if err != nil {
 			return err
 		}
@@ -155,7 +152,7 @@ func (rn *releaseNote) generate(rnFile, changelogFile *os.File) error {
 
 	// Generate the changelog
 	if changelogFile == nil {
-		changelogFile, err = os.OpenFile(path.Join(rn.SubDirPath, "changelog.md"), os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
+		changelogFile, err = os.OpenFile(path.Join(rn.SubDirPath, "changelog.md"), os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0o666)
 		if err != nil {
 			return err
 		}
@@ -304,23 +301,23 @@ func getStringForPullRequestInfos(prPerType prsByType) (string, error) {
 	data := createSortedPrTypeSlice(prPerType)
 
 	t := template.Must(template.New("markdownTemplatePR").Parse(markdownTemplatePR))
-	buff := bytes.Buffer{}
-	if err := t.ExecuteTemplate(&buff, "markdownTemplatePR", data); err != nil {
+	var buf strings.Builder
+	if err := t.ExecuteTemplate(&buf, "markdownTemplatePR", data); err != nil {
 		return "", err
 	}
-	return buff.String(), nil
+	return buf.String(), nil
 }
 
 func getStringForKnownIssues(issues []knownIssue) (string, error) {
 	if len(issues) == 0 {
 		return "", nil
 	}
 	t := template.Must(template.New("markdownTemplateKnownIssues").Parse(markdownTemplateKnownIssues))
-	buff := bytes.Buffer{}
-	if err := t.ExecuteTemplate(&buff, "markdownTemplateKnownIssues", issues); err != nil {
+	var buf strings.Builder
+	if err := t.ExecuteTemplate(&buf, "markdownTemplateKnownIssues", issues); err != nil {
 		return "", err
 	}
-	return buff.String(), nil
+	return buf.String(), nil
 }
 
 func groupAndStringifyPullRequest(pris []pullRequestInformation) (string, error) {
@@ -336,9 +333,7 @@ func groupAndStringifyPullRequest(pris []pullRequestInformation) (string, error)
 }
 
 func main() {
-	var (
-		versionName, summaryFile string
-	)
+	var versionName, summaryFile string
 	pflag.StringVarP(&versionName, "version", "v", "", "name of the version (has to be the following format: v11.0.0)")
 	pflag.StringVarP(&summaryFile, "summary", "s", "", "readme file on which there is a summary of the release")
 	pflag.Parse()

go/vt/binlog/binlog_streamer.go

@@ -251,8 +251,8 @@ func (bls *Streamer) parseEvents(ctx context.Context, events <-chan mysql.Binlog
 	var statements []FullBinlogStatement
 	var format mysql.BinlogFormat
 	var gtid replication.GTID
-	var pos = bls.startPos
-	var autocommit = true
+	pos := bls.startPos
+	autocommit := true
 	var err error
 
 	// Remember the RBR state.
@@ -723,7 +723,7 @@ func (bls *Streamer) appendDeletes(statements []FullBinlogStatement, tce *tableC
 }
 
 // writeValuesAsSQL is a helper method to print the values as SQL in the
-// provided bytes.Buffer. It also returns the value for the keyspaceIDColumn,
+// provided strings.Builder. It also returns the value for the keyspaceIDColumn,
 // and the array of values for the PK, if necessary.
 func writeValuesAsSQL(sql *sqlparser.TrackedBuffer, tce *tableCacheEntry, rs *mysql.Rows, rowIndex int, getPK bool) (sqltypes.Value, []sqltypes.Value, error) {
 	valueIndex := 0
@@ -794,7 +794,7 @@ func writeValuesAsSQL(sql *sqlparser.TrackedBuffer, tce *tableCacheEntry, rs *my
 }
 
 // writeIdentifiersAsSQL is a helper method to print the identifies as SQL in the
-// provided bytes.Buffer. It also returns the value for the keyspaceIDColumn,
+// provided strings.Builder. It also returns the value for the keyspaceIDColumn,
 // and the array of values for the PK, if necessary.
 func writeIdentifiersAsSQL(sql *sqlparser.TrackedBuffer, tce *tableCacheEntry, rs *mysql.Rows, rowIndex int, getPK bool) (sqltypes.Value, []sqltypes.Value, error) {
 	valueIndex := 0

go/vt/hook/hook.go

@@ -17,7 +17,6 @@ limitations under the License.
 package hook
 
 import (
-	"bytes"
 	"context"
 	"errors"
 	"fmt"
@@ -147,7 +146,7 @@ func (hook *Hook) ExecuteContext(ctx context.Context) (result *HookResult) {
 	}
 
 	// Run it.
-	var stdout, stderr bytes.Buffer
+	var stdout, stderr strings.Builder
 	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr
 
@@ -234,7 +233,7 @@ func (hook *Hook) ExecuteAsWritePipe(out io.Writer) (io.WriteCloser, WaitFunc, i
 		return nil, nil, HOOK_GENERIC_ERROR, fmt.Errorf("failed to configure stdin: %v", err)
 	}
 	cmd.Stdout = out
-	var stderr bytes.Buffer
+	var stderr strings.Builder
 	cmd.Stderr = &stderr
 
 	// Start the process.
@@ -273,7 +272,7 @@ func (hook *Hook) ExecuteAsReadPipe(in io.Reader) (io.Reader, WaitFunc, int, err
 		return nil, nil, HOOK_GENERIC_ERROR, fmt.Errorf("failed to configure stdout: %v", err)
 	}
 	cmd.Stdin = in
-	var stderr bytes.Buffer
+	var stderr strings.Builder
 	cmd.Stderr = &stderr
 
 	// Start the process.

go/vt/key/destination.go

@@ -17,7 +17,6 @@ limitations under the License.
 package key
 
 import (
-	"bytes"
 	"encoding/hex"
 	"math/rand"
 	"sort"
@@ -48,7 +47,7 @@ type Destination interface {
 
 // DestinationsString returns a printed version of the destination array.
 func DestinationsString(destinations []Destination) string {
-	var buffer bytes.Buffer
+	var buffer strings.Builder
 	buffer.WriteString("Destinations:")
 	for i, d := range destinations {
 		if i > 0 {
@@ -177,7 +176,7 @@ func (d DestinationExactKeyRanges) Resolve(allShards []*topodatapb.ShardReferenc
 
 // String is part of the Destination interface.
 func (d DestinationExactKeyRanges) String() string {
-	var buffer bytes.Buffer
+	var buffer strings.Builder
 	buffer.WriteString("DestinationExactKeyRanges(")
 	for i, kr := range d {
 		if i > 0 {
@@ -246,7 +245,7 @@ func (d DestinationKeyRanges) Resolve(allShards []*topodatapb.ShardReference, ad
 
 // String is part of the Destination interface.
 func (d DestinationKeyRanges) String() string {
-	var buffer bytes.Buffer
+	var buffer strings.Builder
 	buffer.WriteString("DestinationKeyRanges(")
 	for i, kr := range d {
 		if i > 0 {
@@ -318,7 +317,7 @@ func (d DestinationKeyspaceIDs) Resolve(allShards []*topodatapb.ShardReference,
 
 // String is part of the Destination interface.
 func (d DestinationKeyspaceIDs) String() string {
-	var buffer bytes.Buffer
+	var buffer strings.Builder
 	buffer.WriteString("DestinationKeyspaceIDs(")
 	for i, ksid := range d {
 		if i > 0 {

go/vt/logutil/logger.go

@@ -17,7 +17,6 @@ limitations under the License.
 package logutil
 
 import (
-	"bytes"
 	"fmt"
 	"io"
 	"runtime"
@@ -57,7 +56,7 @@ type Logger interface {
 
 // EventToBuffer formats an individual Event into a buffer, without the
 // final '\n'
-func EventToBuffer(event *logutilpb.Event, buf *bytes.Buffer) {
+func EventToBuffer(event *logutilpb.Event, buf *strings.Builder) {
 	// Avoid Fprintf, for speed. The format is so simple that we
 	// can do it quickly by hand.  It's worth about 3X. Fprintf is hard.
 
@@ -98,8 +97,8 @@ func EventToBuffer(event *logutilpb.Event, buf *bytes.Buffer) {
 
 // EventString returns the line in one string
 func EventString(event *logutilpb.Event) string {
-	buf := new(bytes.Buffer)
-	EventToBuffer(event, buf)
+	var buf strings.Builder
+	EventToBuffer(event, &buf)
 	return buf.String()
 }
 
@@ -251,11 +250,11 @@ func NewMemoryLogger() *MemoryLogger {
 
 // String returns all the lines in one String, separated by '\n'
 func (ml *MemoryLogger) String() string {
-	buf := new(bytes.Buffer)
+	var buf strings.Builder
 	ml.mu.Lock()
 	defer ml.mu.Unlock()
 	for _, event := range ml.Events {
-		EventToBuffer(event, buf)
+		EventToBuffer(event, &buf)
 		buf.WriteByte('\n')
 	}
 	return buf.String()
@@ -355,15 +354,15 @@ func (tl *TeeLogger) Printf(format string, v ...any) {
 const digits = "0123456789"
 
 // twoDigits adds a zero-prefixed two-digit integer to buf
-func twoDigits(buf *bytes.Buffer, value int) {
+func twoDigits(buf *strings.Builder, value int) {
 	buf.WriteByte(digits[value/10])
 	buf.WriteByte(digits[value%10])
 }
 
 // nDigits adds an n-digit integer d to buf
 // padding with pad on the left.
 // It assumes d >= 0.
-func nDigits(buf *bytes.Buffer, n, d int, pad byte) {
+func nDigits(buf *strings.Builder, n, d int, pad byte) {
 	tmp := make([]byte, n)
 	j := n - 1
 	for ; j >= 0 && d > 0; j-- {
@@ -377,7 +376,7 @@ func nDigits(buf *bytes.Buffer, n, d int, pad byte) {
 }
 
 // someDigits adds a zero-prefixed variable-width integer to buf
-func someDigits(buf *bytes.Buffer, d int64) {
+func someDigits(buf *strings.Builder, d int64) {
 	// Print into the top, then copy down.
 	tmp := make([]byte, 10)
 	j := 10