go/vt/sqlparser: improve performance in TrackedBuffer formatting

Two minor things:
* decently improve formatting integers (%d)
* WriteArg calls buf.Grow to avoid potentially 2 allocations

For integer formatting, buf.WriteString(fmt.Sprintf(...)) was about the
worst way to do it. fmt.Sprintf itself allocates a new string, plus it's
%d formatting is much more robust in handling padding and whatnot.

First alternative for free win was using `fmt.Fprintf(&buf, ...)`
instead, which simply avoids the extra allocation and just writes
directly to the buffer.

But strconv.Format{I,Ui}nt is quite fast, especially since it has a fast
path for "small integers".

Here's a trivial benchmark of all 3 options:

```
$ benchstat fmt.txt
goos: darwin
goarch: arm64
pkg: x
                       │   fmt.txt   │
                       │   sec/op    │
FormatInt/Sprintf-10     55.51n ± 1%
FormatInt/Fprintf-10     50.76n ± 1%
FormatInt/FormatInt-10   17.16n ± 2%
geomean                  36.43n

                       │  fmt.txt   │
                       │    B/op    │
FormatInt/Sprintf-10     16.00 ± 0%
FormatInt/Fprintf-10     8.000 ± 0%
FormatInt/FormatInt-10   8.000 ± 0%
geomean                  10.08

                       │  fmt.txt   │
                       │ allocs/op  │
FormatInt/Sprintf-10     2.000 ± 0%
FormatInt/Fprintf-10     1.000 ± 0%
FormatInt/FormatInt-10   1.000 ± 0%
geomean                  1.260
```

So each %d within a format string is considerably faster. This obviously
scales linearly with the number of %d's there are.

Signed-off-by: Matt Robenolt <matt@ydekproductions.com>

go/vt/sqlparser/tracked_buffer.go

@@ -18,6 +18,7 @@ package sqlparser
 
 import (
 	"fmt"
+	"strconv"
 	"strings"
 )
 
@@ -211,7 +212,32 @@ func (buf *TrackedBuffer) astPrintf(currentNode SQLNode, format string, values .
 				}
 			}
 		case 'd':
-			buf.WriteString(fmt.Sprintf("%d", values[fieldnum]))
+			switch v := values[fieldnum].(type) {
+			case int:
+				buf.WriteInt(int64(v))
+			case int8:
+				buf.WriteInt(int64(v))
+			case int16:
+				buf.WriteInt(int64(v))
+			case int32:
+				buf.WriteInt(int64(v))
+			case int64:
+				buf.WriteInt(v)
+			case uint:
+				buf.WriteUint(uint64(v))
+			case uint8:
+				buf.WriteUint(uint64(v))
+			case uint16:
+				buf.WriteUint(uint64(v))
+			case uint32:
+				buf.WriteUint(uint64(v))
+			case uint64:
+				buf.WriteUint(v)
+			case uintptr:
+				buf.WriteUint(uint64(v))
+			default:
+				panic(fmt.Sprintf("unexepcted TrackedBuffer type %T", v))
+			}
 		case 'a':
 			buf.WriteArg("", values[fieldnum].(string))
 		default:
@@ -288,14 +314,26 @@ func areBothISExpr(op Expr, val Expr) bool {
 // WriteArg writes a value argument into the buffer along with
 // tracking information for future substitutions.
 func (buf *TrackedBuffer) WriteArg(prefix, arg string) {
+	length := len(prefix) + len(arg)
 	buf.bindLocations = append(buf.bindLocations, BindLocation{
 		Offset: buf.Len(),
-		Length: len(prefix) + len(arg),
+		Length: length,
 	})
+	buf.Grow(length)
 	buf.WriteString(prefix)
 	buf.WriteString(arg)
 }
 
+// WriteInt writes a signed integer into the buffer.
+func (buf *TrackedBuffer) WriteInt(v int64) {
+	buf.WriteString(strconv.FormatInt(v, 10))
+}
+
+// WriteUint writes an unsigned integer into the buffer.
+func (buf *TrackedBuffer) WriteUint(v uint64) {
+	buf.WriteString(strconv.FormatUint(v, 10))
+}
+
 // ParsedQuery returns a ParsedQuery that contains bind
 // locations for easy substitution.
 func (buf *TrackedBuffer) ParsedQuery() *ParsedQuery {
@@ -335,7 +373,6 @@ func UnescapedString(node SQLNode) string {
 	buf.SetEscapeNoIdentifier()
 	node.Format(buf)
 	return buf.String()
-
 }
 
 // CanonicalString returns a canonical string representation of an SQLNode where all identifiers

go/vt/sqlparser/tracked_buffer_test.go

@@ -295,3 +295,35 @@ func TestCanonicalOutput(t *testing.T) {
 		})
 	}
 }
+
+func TestTrackedBufferMyprintf(t *testing.T) {
+	testcases := []struct {
+		input  string
+		output string
+		args   []any
+	}{
+		{
+			input:  "nothing",
+			output: "nothing",
+			args:   []any{},
+		},
+		{
+			input:  "my name is %s",
+			output: "my name is Homer",
+			args:   []any{"Homer"},
+		},
+		{
+			input:  "%d %d %d %d %d %d %d %d %d %d %d",
+			output: "1 2 3 4 5 6 7 8 9 10 11",
+			args:   []any{int(1), int8(2), int16(3), int32(4), int64(5), uint(6), uint8(7), uint16(8), uint32(9), uint64(10), uintptr(11)},
+		},
+	}
+	for _, tc := range testcases {
+		t.Run(tc.input, func(t *testing.T) {
+			buf := NewTrackedBuffer(nil)
+			buf.Myprintf(tc.input, tc.args...)
+			got := buf.String()
+			assert.Equal(t, tc.output, got)
+		})
+	}
+}