diff --git a/types/helper.go b/types/helper.go
index 91c7733906b24..e3cc4aaf68cd9 100644
--- a/types/helper.go
+++ b/types/helper.go
@@ -114,34 +114,6 @@ func isPunctuation(c byte) bool {
 	return (c >= 0x21 && c <= 0x2F) || (c >= 0x3A && c <= 0x40) || (c >= 0x5B && c <= 0x60) || (c >= 0x7B && c <= 0x7E)
 }
 
-func myMax(a, b int) int {
-	if a > b {
-		return a
-	}
-	return b
-}
-
-func myMaxInt8(a, b int8) int8 {
-	if a > b {
-		return a
-	}
-	return b
-}
-
-func myMin(a, b int) int {
-	if a < b {
-		return a
-	}
-	return b
-}
-
-func myMinInt8(a, b int8) int8 {
-	if a < b {
-		return a
-	}
-	return b
-}
-
 const (
 	maxUint    = uint64(math.MaxUint64)
 	uintCutOff = maxUint/uint64(10) + 1
diff --git a/types/mydecimal.go b/types/mydecimal.go
index 203211265e0c9..37e724ab61370 100644
--- a/types/mydecimal.go
+++ b/types/mydecimal.go
@@ -24,6 +24,7 @@ import (
 	"github.com/pingcap/log"
 	"github.com/pingcap/tidb/parser/mysql"
 	"github.com/pingcap/tidb/parser/terror"
+	"github.com/pingcap/tidb/util/mathutil"
 	"go.uber.org/zap"
 )
 
@@ -353,7 +354,7 @@ func (d *MyDecimal) ToString() (str []byte) {
 		for ; digitsFrac > 0; digitsFrac -= digitsPerWord {
 			x := d.wordBuf[wordIdx]
 			wordIdx++
-			for i := myMin(digitsFrac, digitsPerWord); i > 0; i-- {
+			for i := mathutil.Min(digitsFrac, digitsPerWord); i > 0; i-- {
 				y := x / digMask
 				str[fracIdx] = byte(y) + '0'
 				fracIdx++
@@ -380,7 +381,7 @@ func (d *MyDecimal) ToString() (str []byte) {
 		for ; digitsInt > 0; digitsInt -= digitsPerWord {
 			wordIdx--
 			x := d.wordBuf[wordIdx]
-			for i := myMin(digitsInt, digitsPerWord); i > 0; i-- {
+			for i := mathutil.Min(digitsInt, digitsPerWord); i > 0; i-- {
 				y := x / 10
 				strIdx--
 				str[strIdx] = '0' + byte(x-y*10)
@@ -840,7 +841,7 @@ func (d *MyDecimal) Round(to *MyDecimal, frac int, roundMode RoundMode) (err err
 	if to != d {
 		copy(to.wordBuf[:], d.wordBuf[:])
 		to.negative = d.negative
-		to.digitsInt = int8(myMin(wordsInt, wordBufLen) * digitsPerWord)
+		to.digitsInt = int8(mathutil.Min(wordsInt, wordBufLen) * digitsPerWord)
 	}
 	if wordsFracTo > wordsFrac {
 		idx := wordsInt + wordsFrac
@@ -941,7 +942,7 @@ func (d *MyDecimal) Round(to *MyDecimal, frac int, roundMode RoundMode) (err err
 				frac = wordsFracTo * digitsPerWord
 				err = ErrTruncated
 			}
-			for toIdx = wordsInt + myMax(wordsFracTo, 0); toIdx > 0; toIdx-- {
+			for toIdx = wordsInt + mathutil.Max(wordsFracTo, 0); toIdx > 0; toIdx-- {
 				if toIdx < wordBufLen {
 					to.wordBuf[toIdx] = to.wordBuf[toIdx-1]
 				} else {
@@ -965,7 +966,7 @@ func (d *MyDecimal) Round(to *MyDecimal, frac int, roundMode RoundMode) (err err
 				/* making 'zero' with the proper scale */
 				idx := wordsFracTo + 1
 				to.digitsInt = 1
-				to.digitsFrac = int8(myMax(frac, 0))
+				to.digitsFrac = int8(mathutil.Max(frac, 0))
 				to.negative = false
 				for toIdx < idx {
 					to.wordBuf[toIdx] = 0
@@ -1602,7 +1603,7 @@ func DecimalNeg(from *MyDecimal) *MyDecimal {
 // of `to` may be changed during evaluating.
 func DecimalAdd(from1, from2, to *MyDecimal) error {
 	from1, from2, to = validateArgs(from1, from2, to)
-	to.resultFrac = myMaxInt8(from1.resultFrac, from2.resultFrac)
+	to.resultFrac = mathutil.Max(from1.resultFrac, from2.resultFrac)
 	if from1.negative == from2.negative {
 		return doAdd(from1, from2, to)
 	}
@@ -1613,7 +1614,7 @@ func DecimalAdd(from1, from2, to *MyDecimal) error {
 // DecimalSub subs one decimal from another, sets the result to 'to'.
 func DecimalSub(from1, from2, to *MyDecimal) error {
 	from1, from2, to = validateArgs(from1, from2, to)
-	to.resultFrac = myMaxInt8(from1.resultFrac, from2.resultFrac)
+	to.resultFrac = mathutil.Max(from1.resultFrac, from2.resultFrac)
 	if from1.negative == from2.negative {
 		_, err := doSub(from1, from2, to)
 		return err
@@ -1649,7 +1650,7 @@ func doSub(from1, from2, to *MyDecimal) (cmp int, err error) {
 		wordsFrac1  = digitsToWords(int(from1.digitsFrac))
 		wordsInt2   = digitsToWords(int(from2.digitsInt))
 		wordsFrac2  = digitsToWords(int(from2.digitsFrac))
-		wordsFracTo = myMax(wordsFrac1, wordsFrac2)
+		wordsFracTo = mathutil.Max(wordsFrac1, wordsFrac2)
 
 		start1 = 0
 		stop1  = wordsInt1
@@ -1814,8 +1815,8 @@ func doAdd(from1, from2, to *MyDecimal) error {
 		wordsFrac1  = digitsToWords(int(from1.digitsFrac))
 		wordsInt2   = digitsToWords(int(from2.digitsInt))
 		wordsFrac2  = digitsToWords(int(from2.digitsFrac))
-		wordsIntTo  = myMax(wordsInt1, wordsInt2)
-		wordsFracTo = myMax(wordsFrac1, wordsFrac2)
+		wordsIntTo  = mathutil.Max(wordsInt1, wordsInt2)
+		wordsFracTo = mathutil.Max(wordsFrac1, wordsFrac2)
 	)
 
 	var x int32
@@ -1839,7 +1840,7 @@ func doAdd(from1, from2, to *MyDecimal) error {
 	idxTo := wordsIntTo + wordsFracTo
 	to.negative = from1.negative
 	to.digitsInt = int8(wordsIntTo * digitsPerWord)
-	to.digitsFrac = myMaxInt8(from1.digitsFrac, from2.digitsFrac)
+	to.digitsFrac = mathutil.Max(from1.digitsFrac, from2.digitsFrac)
 
 	if err != nil {
 		if to.digitsFrac > int8(wordsFracTo*digitsPerWord) {
@@ -1977,7 +1978,7 @@ func DecimalMul(from1, from2, to *MyDecimal) error {
 		tmp1        = wordsIntTo
 		tmp2        = wordsFracTo
 	)
-	to.resultFrac = myMinInt8(from1.resultFrac+from2.resultFrac, mysql.MaxDecimalScale)
+	to.resultFrac = mathutil.Min(from1.resultFrac+from2.resultFrac, mysql.MaxDecimalScale)
 	wordsIntTo, wordsFracTo, err = fixWordCntError(wordsIntTo, wordsFracTo)
 	to.negative = from1.negative != from2.negative
 	to.digitsFrac = from1.digitsFrac + from2.digitsFrac
@@ -2092,7 +2093,7 @@ func DecimalMul(from1, from2, to *MyDecimal) error {
 // fracIncr - increment of fraction
 func DecimalDiv(from1, from2, to *MyDecimal, fracIncr int) error {
 	from1, from2, to = validateArgs(from1, from2, to)
-	to.resultFrac = myMinInt8(from1.resultFrac+int8(fracIncr), mysql.MaxDecimalScale)
+	to.resultFrac = mathutil.Min(from1.resultFrac+int8(fracIncr), mysql.MaxDecimalScale)
 	return doDivMod(from1, from2, to, nil, fracIncr)
 }
 
@@ -2122,7 +2123,7 @@ DecimalMod does modulus of two decimals.
 */
 func DecimalMod(from1, from2, to *MyDecimal) error {
 	from1, from2, to = validateArgs(from1, from2, to)
-	to.resultFrac = myMaxInt8(from1.resultFrac, from2.resultFrac)
+	to.resultFrac = mathutil.Max(from1.resultFrac, from2.resultFrac)
 	return doDivMod(from1, from2, nil, to, 0)
 }
 
@@ -2190,7 +2191,7 @@ func doDivMod(from1, from2, to, mod *MyDecimal, fracIncr int) error {
 		// digitsFrac=max(frac1, frac2), as for subtraction
 		// digitsInt=from2.digitsInt
 		to.negative = from1.negative
-		to.digitsFrac = myMaxInt8(from1.digitsFrac, from2.digitsFrac)
+		to.digitsFrac = mathutil.Max(from1.digitsFrac, from2.digitsFrac)
 	} else {
 		wordsFracTo = digitsToWords(frac1 + frac2 + fracIncr)
 		wordsIntTo, wordsFracTo, err = fixWordCntError(wordsIntTo, wordsFracTo)
@@ -2355,7 +2356,7 @@ func doDivMod(from1, from2, to, mod *MyDecimal, fracIncr int) error {
 				return ErrOverflow
 			}
 			stop1 = start1 + wordsIntTo + wordsFracTo
-			to.digitsInt = int8(myMin(wordsIntTo*digitsPerWord, int(from2.digitsInt)))
+			to.digitsInt = int8(mathutil.Min(wordsIntTo*digitsPerWord, int(from2.digitsInt)))
 		}
 		if wordsIntTo+wordsFracTo > wordBufLen {
 			stop1 -= wordsIntTo + wordsFracTo - wordBufLen