dialect/sql/sqlbuild: replace bytes.buffer with strings.builder (#1502)

benchmark                                      old ns/op     new ns/op     delta
BenchmarkInsertBuilder_Default/sqlite3-16      285           253           -11.06%
BenchmarkInsertBuilder_Default/mysql-16        283           219           -22.70%
BenchmarkInsertBuilder_Default/postgres-16     374           340           -9.17%
BenchmarkInsertBuilder_Small/sqlite3-16        1945          1734          -10.85%
BenchmarkInsertBuilder_Small/mysql-16          1957          1741          -11.04%
BenchmarkInsertBuilder_Small/postgres-16       2393          2220          -7.23%

benchmark                                      old allocs     new allocs     delta
BenchmarkInsertBuilder_Default/sqlite3-16      5              6              +20.00%
BenchmarkInsertBuilder_Default/mysql-16        5              5              +0.00%
BenchmarkInsertBuilder_Default/postgres-16     6              7              +16.67%
BenchmarkInsertBuilder_Small/sqlite3-16        22             23             +4.55%
BenchmarkInsertBuilder_Small/mysql-16          22             23             +4.55%
BenchmarkInsertBuilder_Small/postgres-16       31             32             +3.23%

benchmark                                      old bytes     new bytes     delta
BenchmarkInsertBuilder_Default/sqlite3-16      456           168           -63.16%
BenchmarkInsertBuilder_Default/mysql-16        440           104           -76.36%
BenchmarkInsertBuilder_Default/postgres-16     480           176           -63.33%
BenchmarkInsertBuilder_Small/sqlite3-16        1624          1176          -27.59%
BenchmarkInsertBuilder_Small/mysql-16          1624          1176          -27.59%
BenchmarkInsertBuilder_Small/postgres-16       1656          1192          -28.02%

dialect/sql/builder.go

@@ -12,7 +12,6 @@
 package sql
 
 import (
-	"bytes"
 	"context"
 	"database/sql/driver"
 	"fmt"
@@ -738,11 +737,9 @@ func (i *InsertBuilder) Query() (string, []interface{}) {
 			i.WriteByte('(').Args(v...).WriteByte(')')
 		}
 	}
-
 	if len(i.conflictColumns) > 0 {
 		i.buildConflictHandling()
 	}
-
 	if len(i.returning) > 0 && i.postgres() {
 		i.WriteString(" RETURNING ")
 		i.IdentComma(i.returning...)
@@ -2232,11 +2229,11 @@ func (n Queries) Query() (string, []interface{}) {
 
 // Builder is the base query builder for the sql dsl.
 type Builder struct {
-	bytes.Buffer               // underlying buffer.
+	sb      *strings.Builder // underlying builder.
-	dialect      string        // configured dialect.
+	dialect string           // configured dialect.
-	args         []interface{} // query parameters.
+	args    []interface{}    // query parameters.
-	total        int           // total number of parameters in query tree.
+	total   int              // total number of parameters in query tree.
-	errs         []error       // errors that added during the query construction.
+	errs    []error          // errors that added during the query construction.
 }
 
 // Quote quotes the given identifier with the characters based
@@ -2285,15 +2282,45 @@ func (b *Builder) IdentComma(s ...string) *Builder {
 	return b
 }
 
+// String returns the accumulated string.
+func (b *Builder) String() string {
+	if b.sb == nil {
+		return ""
+	}
+	return b.sb.String()
+}
+
 // WriteByte wraps the Buffer.WriteByte to make it chainable with other methods.
 func (b *Builder) WriteByte(c byte) *Builder {
-	b.Buffer.WriteByte(c)
+	if b.sb == nil {
+		b.sb = &strings.Builder{}
+	}
+	b.sb.WriteByte(c)
 	return b
 }
 
 // WriteString wraps the Buffer.WriteString to make it chainable with other methods.
 func (b *Builder) WriteString(s string) *Builder {
-	b.Buffer.WriteString(s)
+	if b.sb == nil {
+		b.sb = &strings.Builder{}
+	}
+	b.sb.WriteString(s)
+	return b
+}
+
+// Len returns the number of accumulated bytes.
+func (b *Builder) Len() int {
+	if b.sb == nil {
+		return 0
+	}
+	return b.sb.Len()
+}
+
+// Reset resets the Builder to be empty.
+func (b *Builder) Reset() *Builder {
+	if b.sb != nil {
+		b.sb.Reset()
+	}
 	return b
 }
 
@@ -2467,11 +2494,11 @@ func (b *Builder) join(qs []Querier, sep string) *Builder {
 
 // Nested gets a callback, and wraps its result with parentheses.
 func (b *Builder) Nested(f func(*Builder)) *Builder {
-	nb := &Builder{dialect: b.dialect, total: b.total}
+	nb := &Builder{dialect: b.dialect, total: b.total, sb: &strings.Builder{}}
 	nb.WriteByte('(')
 	f(nb)
 	nb.WriteByte(')')
-	nb.WriteTo(b)
+	b.WriteString(nb.String())
 	b.args = append(b.args, nb.args...)
 	b.total = nb.total
 	return b
@@ -2505,11 +2532,13 @@ func (b Builder) Query() (string, []interface{}) {
 
 // clone returns a shallow clone of a builder.
 func (b Builder) clone() Builder {
-	c := Builder{dialect: b.dialect, total: b.total}
+	c := Builder{dialect: b.dialect, total: b.total, sb: &strings.Builder{}}
 	if len(b.args) > 0 {
 		c.args = append(c.args, b.args...)
 	}
-	c.Buffer.Write(b.Bytes())
+	if b.sb != nil {
+		c.sb.WriteString(b.sb.String())
+	}
 	return c
 }