planner: optimize the performance of PlanCacheParamList.String() (p…

…ingcap#46592)

close pingcap#46579

executor/show_stats_test.go

@@ -53,7 +53,7 @@ func TestShowStatsLocked(t *testing.T) {
 	tk.MustExec("create table t (a int, b int)")
 	tk.MustExec("create table t1 (a int, b int)")
 	tk.MustExec("lock stats t, t1")
-	result := tk.MustQuery("show stats_locked")
+	result := tk.MustQuery("show stats_locked").Sort()
 	require.Len(t, result.Rows(), 2)
 	require.Equal(t, "t", result.Rows()[0][1])
 	require.Equal(t, "t1", result.Rows()[1][1])

types/datum.go

@@ -21,6 +21,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 	"unicode/utf8"
 	"unsafe"
@@ -2283,39 +2284,63 @@ func (ds *datumsSorter) Swap(i, j int) {
 	ds.datums[i], ds.datums[j] = ds.datums[j], ds.datums[i]
 }
 
+var strBuilderPool = sync.Pool{New: func() interface{} { return &strings.Builder{} }}
+
 // DatumsToString converts several datums to formatted string.
 func DatumsToString(datums []Datum, handleSpecialValue bool) (string, error) {
-	strs := make([]string, 0, len(datums))
-	for _, datum := range datums {
+	n := len(datums)
+	builder := strBuilderPool.Get().(*strings.Builder)
+	defer func() {
+		builder.Reset()
+		strBuilderPool.Put(builder)
+	}()
+	if n > 1 {
+		builder.WriteString("(")
+	}
+	for i, datum := range datums {
+		if i > 0 {
+			builder.WriteString(", ")
+		}
 		if handleSpecialValue {
 			switch datum.Kind() {
 			case KindNull:
-				strs = append(strs, "NULL")
+				builder.WriteString("NULL")
 				continue
 			case KindMinNotNull:
-				strs = append(strs, "-inf")
+				builder.WriteString("-inf")
 				continue
 			case KindMaxValue:
-				strs = append(strs, "+inf")
+				builder.WriteString("+inf")
 				continue
 			}
 		}
 		str, err := datum.ToString()
 		if err != nil {
 			return "", errors.Trace(err)
 		}
+		const logDatumLen = 2048
+		originalLen := -1
+		if len(str) > logDatumLen {
+			originalLen = len(str)
+			str = str[:logDatumLen]
+		}
 		if datum.Kind() == KindString {
-			strs = append(strs, fmt.Sprintf("%q", str))
+			builder.WriteString(`"`)
+			builder.WriteString(str)
+			builder.WriteString(`"`)
 		} else {
-			strs = append(strs, str)
+			builder.WriteString(str)
+		}
+		if originalLen != -1 {
+			builder.WriteString(" len(")
+			builder.WriteString(strconv.Itoa(originalLen))
+			builder.WriteString(")")
 		}
 	}
-	size := len(datums)
-	if size > 1 {
-		strs[0] = "(" + strs[0]
-		strs[size-1] = strs[size-1] + ")"
+	if n > 1 {
+		builder.WriteString(")")
 	}
-	return strings.Join(strs, ", "), nil
+	return builder.String(), nil
 }
 
 // DatumsToStrNoErr converts some datums to a formatted string.

types/datum_test.go

@@ -20,6 +20,7 @@ import (
 	"math"
 	"reflect"
 	"strconv"
+	"strings"
 	"testing"
 	"time"
 
@@ -704,3 +705,79 @@ func TestNULLNotEqualWithOthers(t *testing.T) {
 		require.NotEqual(t, 0, result)
 	}
 }
+
+func TestDatumsToString(t *testing.T) {
+	datums := []Datum{
+		NewIntDatum(1),
+		NewUintDatum(2),
+		NewFloat32Datum(-3.1111111),
+		NewFloat64Datum(4.123),
+		NewDatum(math.Inf(5)),
+		NewDecimalDatum(NewDecFromStringForTest("6.6")),
+		NewStringDatum("abc"),
+		NewCollationStringDatum("", charset.CollationBin),
+		NewDurationDatum(Duration{Duration: time.Duration(11111)}),
+		NewTimeDatum(ZeroTime),
+		NewBytesDatum([]byte("xxx")),
+		NewBinaryLiteralDatum([]byte{}),
+		NewJSONDatum(CreateBinaryJSON(nil)),
+		MinNotNullDatum(),
+		MaxValueDatum(),
+	}
+	str, err := DatumsToString(datums, true)
+	require.NoError(t, err)
+	require.Equal(t, str, `(1, 2, -3.1111112, 4.123, +Inf, 6.6, "abc", "", 00:00:00, 0000-00-00 00:00:00, xxx, , null, -inf, +inf)`)
+}
+
+func BenchmarkDatumsToString(b *testing.B) {
+	datums := []Datum{
+		NewIntDatum(1),
+		NewUintDatum(2),
+		NewFloat32Datum(-3.1111111),
+		NewFloat64Datum(4.123),
+		NewDatum(math.Inf(5)),
+		NewDecimalDatum(NewDecFromStringForTest("6.66666")),
+		NewStringDatum("dklsfjkaslnfwoiewlkfjaslkfjljs"),
+		NewCollationStringDatum("1234567890-=12345656789", charset.CollationBin),
+		NewDurationDatum(Duration{Duration: time.Duration(11111)}),
+		NewTimeDatum(ZeroTime),
+		NewBytesDatum([]byte("xxxxxxxxxxxxxxxxxxxxxxx")),
+		NewBinaryLiteralDatum([]byte{}),
+		NewJSONDatum(CreateBinaryJSON(nil)),
+		MinNotNullDatum(),
+		MaxValueDatum(),
+	}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, err := DatumsToString(datums, true)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func BenchmarkDatumsToStringStr(b *testing.B) {
+	datums := []Datum{
+		NewStringDatum(strings.Repeat("1", 512)),
+	}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, err := DatumsToString(datums, true)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func BenchmarkDatumsToStringLongStr(b *testing.B) {
+	datums := []Datum{
+		NewStringDatum(strings.Repeat("1", 1024*10)), // 10KB
+	}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, err := DatumsToString(datums, true)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}