Placeholder interpolation

.travis.yml

@@ -1,8 +1,8 @@
 language: go
 go:
-  - 1.1
   - 1.2
   - 1.3
+  - 1.4
   - tip
 
 before_script:

README.md

@@ -182,6 +182,19 @@ SELECT u.id FROM users as u
 
 will return `u.id` instead of just `id` if `columnsWithAlias=true`.
 
+##### `interpolateParams`
+
+```
+Type:           bool
+Valid Values:   true, false
+Default:        false
+```
+
+When `interpolateParams` is true, calls to `sql.Db.Query()` and `sql.Db.Exec()` with params interpolates placeholders (`?`) with given params. This reduces roundtrips to database compared with `interpolateParams=false` since it uses prepare, exec and close to support parameters.
+
+NOTE: *This may introduce a SQL injection vulnerability when connection encoding is multibyte encoding except for UTF-8 (e.g. CP932)!*
+(See http://stackoverflow.com/a/12118602/3430118)
+
 ##### `loc`
 
 ```

benchmark_test.go

@@ -11,10 +11,13 @@ package mysql
 import (
 	"bytes"
 	"database/sql"
+	"database/sql/driver"
+	"math"
 	"strings"
 	"sync"
 	"sync/atomic"
 	"testing"
+	"time"
 )
 
 type TB testing.B
@@ -45,7 +48,11 @@ func initDB(b *testing.B, queries ...string) *sql.DB {
 	db := tb.checkDB(sql.Open("mysql", dsn))
 	for _, query := range queries {
 		if _, err := db.Exec(query); err != nil {
-			b.Fatalf("Error on %q: %v", query, err)
+			if w, ok := err.(MySQLWarnings); ok {
+				b.Logf("Warning on %q: %v", query, w)
+			} else {
+				b.Fatalf("Error on %q: %v", query, err)
+			}
 		}
 	}
 	return db
@@ -206,3 +213,33 @@ func BenchmarkRoundtripBin(b *testing.B) {
 		rows.Close()
 	}
 }
+
+func BenchmarkInterpolation(b *testing.B) {
+	mc := &mysqlConn{
+		cfg: &config{
+			interpolateParams: true,
+			loc:               time.UTC,
+		},
+		maxPacketAllowed: maxPacketSize,
+		maxWriteSize:     maxPacketSize - 1,
+	}
+
+	args := []driver.Value{
+		int64(42424242),
+		float64(math.Pi),
+		false,
+		time.Unix(1423411542, 807015000),
+		[]byte("bytes containing special chars ' \" \a \x00"),
+		"string containing special chars ' \" \a \x00",
+	}
+	q := "SELECT ?, ?, ?, ?, ?, ?"
+
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, err := mc.interpolateParams(q, args)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}

connection.go

@@ -13,6 +13,7 @@ import (
 	"database/sql/driver"
 	"errors"
 	"net"
+	"strconv"
 	"strings"
 	"time"
 )
@@ -26,6 +27,7 @@ type mysqlConn struct {
 	maxPacketAllowed int
 	maxWriteSize     int
 	flags            clientFlag
+	status           statusFlag
 	sequence         uint8
 	parseTime        bool
 	strict           bool
@@ -46,6 +48,7 @@ type config struct {
 	allowOldPasswords bool
 	clientFoundRows   bool
 	columnsWithAlias  bool
+	interpolateParams bool
 }
 
 // Handles parameters set in DSN after the connection is established
@@ -162,28 +165,174 @@ func (mc *mysqlConn) Prepare(query string) (driver.Stmt, error) {
 	return stmt, err
 }
 
+// estimateParamLength calculates upper bound of string length from types.
+func estimateParamLength(args []driver.Value) (int, bool) {
+	l := 0
+	for _, a := range args {
+		switch v := a.(type) {
+		case int64, float64:
+			// 24 (-1.7976931348623157e+308) may be upper bound. But I'm not sure.
+			l += 25
+		case bool:
+			l += 1 // 0 or 1
+		case time.Time:
+			l += 30 // '1234-12-23 12:34:56.777777'
+		case string:
+			l += len(v)*2 + 2
+		case []byte:
+			l += len(v)*2 + 2
+		default:
+			return 0, false
+		}
+	}
+	return l, true
+}
+
+func (mc *mysqlConn) interpolateParams(query string, args []driver.Value) (string, error) {
+	estimated, ok := estimateParamLength(args)
+	if !ok {
+		return "", driver.ErrSkip
+	}
+	estimated += len(query)
+
+	buf := make([]byte, 0, estimated)
+	argPos := 0
+
+	for i := 0; i < len(query); i++ {
+		q := strings.IndexByte(query[i:], '?')
+		if q == -1 {
+			buf = append(buf, query[i:]...)
+			break
+		}
+		buf = append(buf, query[i:i+q]...)
+		i += q
+
+		arg := args[argPos]
+		argPos++
+
+		if arg == nil {
+			buf = append(buf, "NULL"...)
+			continue
+		}
+
+		switch v := arg.(type) {
+		case int64:
+			buf = strconv.AppendInt(buf, v, 10)
+		case float64:
+			buf = strconv.AppendFloat(buf, v, 'g', -1, 64)
+		case bool:
+			if v {
+				buf = append(buf, '1')
+			} else {
+				buf = append(buf, '0')
+			}
+		case time.Time:
+			if v.IsZero() {
+				buf = append(buf, "'0000-00-00'"...)
+			} else {
+				v := v.In(mc.cfg.loc)
+				v = v.Add(time.Nanosecond * 500) // To round under microsecond
+				year := v.Year()
+				year100 := year / 100
+				year1 := year % 100
+				month := v.Month()
+				day := v.Day()
+				hour := v.Hour()
+				minute := v.Minute()
+				second := v.Second()
+				micro := v.Nanosecond() / 1000
+
+				buf = append(buf, []byte{
+					'\'',
+					digits10[year100], digits01[year100],
+					digits10[year1], digits01[year1],
+					'-',
+					digits10[month], digits01[month],
+					'-',
+					digits10[day], digits01[day],
+					' ',
+					digits10[hour], digits01[hour],
+					':',
+					digits10[minute], digits01[minute],
+					':',
+					digits10[second], digits01[second],
+				}...)
+
+				if micro != 0 {
+					micro10000 := micro / 10000
+					micro100 := micro / 100 % 100
+					micro1 := micro % 100
+					buf = append(buf, []byte{
+						'.',
+						digits10[micro10000], digits01[micro10000],
+						digits10[micro100], digits01[micro100],
+						digits10[micro1], digits01[micro1],
+					}...)
+				}
+				buf = append(buf, '\'')
+			}
+		case []byte:
+			if v == nil {
+				buf = append(buf, "NULL"...)
+			} else {
+				buf = append(buf, '\'')
+				if mc.status&statusNoBackslashEscapes == 0 {
+					buf = escapeBytesBackslash(buf, v)
+				} else {
+					buf = escapeBytesQuotes(buf, v)
+				}
+				buf = append(buf, '\'')
+			}
+		case string:
+			buf = append(buf, '\'')
+			if mc.status&statusNoBackslashEscapes == 0 {
+				buf = escapeStringBackslash(buf, v)
+			} else {
+				buf = escapeStringQuotes(buf, v)
+			}
+			buf = append(buf, '\'')
+		default:
+			return "", driver.ErrSkip
+		}
+
+		if len(buf)+4 > mc.maxPacketAllowed {
+			return "", driver.ErrSkip
+		}
+	}
+	if argPos != len(args) {
+		return "", driver.ErrSkip
+	}
+	return string(buf), nil
+}
+
 func (mc *mysqlConn) Exec(query string, args []driver.Value) (driver.Result, error) {
 	if mc.netConn == nil {
 		errLog.Print(ErrInvalidConn)
 		return nil, driver.ErrBadConn
 	}
-	if len(args) == 0 { // no args, fastpath
-		mc.affectedRows = 0
-		mc.insertId = 0
-
-		err := mc.exec(query)
-		if err == nil {
-			return &mysqlResult{
-				affectedRows: int64(mc.affectedRows),
-				insertId:     int64(mc.insertId),
-			}, err
+	if len(args) != 0 {
+		if !mc.cfg.interpolateParams {
+			return nil, driver.ErrSkip
 		}
-		return nil, err
+		// try to interpolate the parameters to save extra roundtrips for preparing and closing a statement
+		prepared, err := mc.interpolateParams(query, args)
+		if err != nil {
+			return nil, err
+		}
+		query = prepared
+		args = nil
 	}
+	mc.affectedRows = 0
+	mc.insertId = 0
 
-	// with args, must use prepared stmt
-	return nil, driver.ErrSkip
-
+	err := mc.exec(query)
+	if err == nil {
+		return &mysqlResult{
+			affectedRows: int64(mc.affectedRows),
+			insertId:     int64(mc.insertId),
+		}, err
+	}
+	return nil, err
 }
 
 // Internal function to execute commands
@@ -212,31 +361,38 @@ func (mc *mysqlConn) Query(query string, args []driver.Value) (driver.Rows, erro
 		errLog.Print(ErrInvalidConn)
 		return nil, driver.ErrBadConn
 	}
-	if len(args) == 0 { // no args, fastpath
-		// Send command
-		err := mc.writeCommandPacketStr(comQuery, query)
+	if len(args) != 0 {
+		if !mc.cfg.interpolateParams {
+			return nil, driver.ErrSkip
+		}
+		// try client-side prepare to reduce roundtrip
+		prepared, err := mc.interpolateParams(query, args)
+		if err != nil {
+			return nil, err
+		}
+		query = prepared
+		args = nil
+	}
+	// Send command
+	err := mc.writeCommandPacketStr(comQuery, query)
+	if err == nil {
+		// Read Result
+		var resLen int
+		resLen, err = mc.readResultSetHeaderPacket()
 		if err == nil {
-			// Read Result
-			var resLen int
-			resLen, err = mc.readResultSetHeaderPacket()
-			if err == nil {
-				rows := new(textRows)
-				rows.mc = mc
-
-				if resLen == 0 {
-					// no columns, no more data
-					return emptyRows{}, nil
-				}
-				// Columns
-				rows.columns, err = mc.readColumns(resLen)
-				return rows, err
+			rows := new(textRows)
+			rows.mc = mc
+
+			if resLen == 0 {
+				// no columns, no more data
+				return emptyRows{}, nil
 			}
+			// Columns
+			rows.columns, err = mc.readColumns(resLen)
+			return rows, err
 		}
-		return nil, err
 	}
-
-	// with args, must use prepared stmt
-	return nil, driver.ErrSkip
+	return nil, err
 }
 
 // Gets the value of the given MySQL System Variable

const.go

@@ -130,3 +130,25 @@ const (
 	flagUnknown3
 	flagUnknown4
 )
+
+// http://dev.mysql.com/doc/internals/en/status-flags.html
+
+type statusFlag uint16
+
+const (
+	statusInTrans statusFlag = 1 << iota
+	statusInAutocommit
+	statusReserved // Not in documentation
+	statusMoreResultsExists
+	statusNoGoodIndexUsed
+	statusNoIndexUsed
+	statusCursorExists
+	statusLastRowSent
+	statusDbDropped
+	statusNoBackslashEscapes
+	statusMetadataChanged
+	statusQueryWasSlow
+	statusPsOutParams
+	statusInTransReadonly
+	statusSessionStateChanged
+)