From afdf9a4ef6fc4165d3edd8bb8fa5a6bb7c191b92 Mon Sep 17 00:00:00 2001
From: zhaoxingyu <zhaoxingyu19920404@gmail.com>
Date: Tue, 29 Mar 2016 15:39:03 +0800
Subject: [PATCH] Change mysql.Time to ptr in datum.

In this way, we can save the cost of the alloc of mysql.Time in interface.
In the future, we will change all mysql.Time to ptr to save the cost of copy mysql.Time struct.
---
 evaluator/builtin_time.go  |  4 ++--
 mysql/time.go              | 12 +++++++++---
 tidb-server/server/util.go |  2 +-
 util/types/datum.go        | 20 +++++++++++++-------
 4 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/evaluator/builtin_time.go b/evaluator/builtin_time.go
index b28778191f..baacb77d05 100644
--- a/evaluator/builtin_time.go
+++ b/evaluator/builtin_time.go
@@ -184,7 +184,7 @@ func builtinNow(args []types.Datum, _ context.Context) (d types.Datum, err error
 		d.SetNull()
 		return d, errors.Trace(err)
 	}
-	d.SetMysqlTime(tr)
+	d.SetMysqlTime(&tr)
 	return d, nil
 }
 
@@ -373,7 +373,7 @@ func builtinCurrentDate(args []types.Datum, _ context.Context) (d types.Datum, e
 	t := mysql.Time{
 		Time: time.Date(year, month, day, 0, 0, 0, 0, time.Local),
 		Type: mysql.TypeDate, Fsp: 0}
-	d.SetMysqlTime(t)
+	d.SetMysqlTime(&t)
 	return d, nil
 }
 
diff --git a/mysql/time.go b/mysql/time.go
index 7f98199415..678a5bc34f 100644
--- a/mysql/time.go
+++ b/mysql/time.go
@@ -280,7 +280,10 @@ func (t Time) ConvertToDuration() (Duration, error) {
 
 // Compare returns an integer comparing the time instant t to o.
 // If t is after o, return 1, equal o, return 0, before o, return -1.
-func (t Time) Compare(o Time) int {
+func (t *Time) Compare(o *Time) int {
+	if o == nil {
+		return 1
+	}
 	if t.Time.After(o.Time) {
 		return 1
 	} else if t.Time.Equal(o.Time) {
@@ -299,7 +302,7 @@ func (t Time) CompareString(str string) (int, error) {
 		return 0, errors.Trace(err)
 	}
 
-	return t.Compare(o), nil
+	return t.Compare(&o), nil
 }
 
 // RoundFrac rounds fractional seconds precision with new fsp and returns a new one.
@@ -1027,7 +1030,10 @@ func checkTimestamp(t Time) bool {
 }
 
 // ExtractTimeNum extracts time value number from time unit and format.
-func ExtractTimeNum(unit string, t Time) (int64, error) {
+func ExtractTimeNum(unit string, t *Time) (int64, error) {
+	if t == nil {
+		return 0, errors.Errorf("invalid time t")
+	}
 	switch strings.ToUpper(unit) {
 	case "MICROSECOND":
 		return int64(t.Nanosecond() / 1000), nil
diff --git a/tidb-server/server/util.go b/tidb-server/server/util.go
index 4d6c76d3d7..c143f48bf3 100644
--- a/tidb-server/server/util.go
+++ b/tidb-server/server/util.go
@@ -293,7 +293,7 @@ func dumpRowValuesBinary(alloc arena.Allocator, columns []*ColumnInfo, row []typ
 		case types.KindMysqlDecimal:
 			data = append(data, dumpLengthEncodedString(hack.Slice(val.GetMysqlDecimal().String()), alloc)...)
 		case types.KindMysqlTime:
-			data = append(data, dumpBinaryDateTime(val.GetMysqlTime(), nil)...)
+			data = append(data, dumpBinaryDateTime(*val.GetMysqlTime(), nil)...)
 		case types.KindMysqlDuration:
 			data = append(data, dumpBinaryTime(val.GetMysqlDuration().Duration)...)
 		case types.KindMysqlSet:
diff --git a/util/types/datum.go b/util/types/datum.go
index fc5744e8be..6d038342ed 100644
--- a/util/types/datum.go
+++ b/util/types/datum.go
@@ -233,12 +233,12 @@ func (d *Datum) SetMysqlSet(b mysql.Set) {
 }
 
 // GetMysqlTime gets mysql.Time value
-func (d *Datum) GetMysqlTime() mysql.Time {
-	return d.x.(mysql.Time)
+func (d *Datum) GetMysqlTime() *mysql.Time {
+	return d.x.(*mysql.Time)
 }
 
 // SetMysqlTime sets mysql.Time value
-func (d *Datum) SetMysqlTime(b mysql.Time) {
+func (d *Datum) SetMysqlTime(b *mysql.Time) {
 	d.k = KindMysqlTime
 	d.x = b
 }
@@ -258,6 +258,8 @@ func (d *Datum) GetValue() interface{} {
 		return d.GetString()
 	case KindBytes:
 		return d.GetBytes()
+	case KindMysqlTime:
+		return *d.GetMysqlTime()
 	default:
 		return d.x
 	}
@@ -306,9 +308,10 @@ func (d *Datum) SetValue(val interface{}) {
 	case mysql.Set:
 		d.x = x
 		d.k = KindMysqlSet
+	case *mysql.Time:
+		d.SetMysqlTime(x)
 	case mysql.Time:
-		d.x = x
-		d.k = KindMysqlTime
+		d.SetMysqlTime(&x)
 	case []Datum:
 		d.x = x
 		d.k = KindRow
@@ -458,7 +461,7 @@ func (d *Datum) compareString(s string) (int, error) {
 		return d.GetMysqlDecimal().Cmp(dec), err
 	case KindMysqlTime:
 		dt, err := mysql.ParseDatetime(s)
-		return d.GetMysqlTime().Compare(dt), err
+		return d.GetMysqlTime().Compare(&dt), err
 	case KindMysqlDuration:
 		dur, err := mysql.ParseDuration(s, mysql.MaxFsp)
 		return d.GetMysqlDuration().Compare(dur), err
@@ -544,7 +547,10 @@ func (d *Datum) compareMysqlSet(set mysql.Set) (int, error) {
 	}
 }
 
-func (d *Datum) compareMysqlTime(time mysql.Time) (int, error) {
+func (d *Datum) compareMysqlTime(time *mysql.Time) (int, error) {
+	if time == nil {
+		return 0, errors.Errorf("invalid time t")
+	}
 	switch d.k {
 	case KindString, KindBytes:
 		dt, err := mysql.ParseDatetime(d.GetString())