expression: fix the wrong rounding behavior of Decimal

executor/aggfuncs/func_avg.go

@@ -81,7 +81,7 @@ func (e *baseAvgDecimal) AppendFinalResult2Chunk(sctx sessionctx.Context, pr Par
 	if frac == -1 {
 		frac = mysql.MaxDecimalScale
 	}
-	err = finalResult.Round(finalResult, frac, types.ModeHalfEven)
+	err = finalResult.Round(finalResult, frac, types.ModeHalfUp)
 	if err != nil {
 		return err
 	}
@@ -276,7 +276,7 @@ func (e *avgOriginal4DistinctDecimal) AppendFinalResult2Chunk(sctx sessionctx.Co
 	if frac == -1 {
 		frac = mysql.MaxDecimalScale
 	}
-	err = finalResult.Round(finalResult, frac, types.ModeHalfEven)
+	err = finalResult.Round(finalResult, frac, types.ModeHalfUp)
 	if err != nil {
 		return err
 	}

executor/aggfuncs/func_first_row.go

@@ -485,7 +485,7 @@ func (e *firstRow4Decimal) AppendFinalResult2Chunk(sctx sessionctx.Context, pr P
 	if frac == -1 {
 		frac = mysql.MaxDecimalScale
 	}
-	err := p.val.Round(&p.val, frac, types.ModeHalfEven)
+	err := p.val.Round(&p.val, frac, types.ModeHalfUp)
 	if err != nil {
 		return err
 	}

executor/aggfuncs/func_max_min.go

@@ -822,7 +822,7 @@ func (e *maxMin4Decimal) AppendFinalResult2Chunk(sctx sessionctx.Context, pr Par
 	if frac == -1 {
 		frac = mysql.MaxDecimalScale
 	}
-	err := p.val.Round(&p.val, frac, types.ModeHalfEven)
+	err := p.val.Round(&p.val, frac, types.ModeHalfUp)
 	if err != nil {
 		return err
 	}

executor/aggfuncs/func_sum.go

@@ -178,7 +178,7 @@ func (e *sum4Decimal) AppendFinalResult2Chunk(sctx sessionctx.Context, pr Partia
 	if frac == -1 {
 		frac = mysql.MaxDecimalScale
 	}
-	err := p.val.Round(&p.val, frac, types.ModeHalfEven)
+	err := p.val.Round(&p.val, frac, types.ModeHalfUp)
 	if err != nil {
 		return err
 	}

executor/insert_test.go

@@ -1940,3 +1940,22 @@ func TestInsertIntoSelectError(t *testing.T) {
 	tk.MustQuery("SELECT * FROM t1;").Check(testkit.Rows("0", "0", "0"))
 	tk.MustExec("DROP TABLE t1;")
 }
+
+// https://github.com/pingcap/tidb/issues/32213.
+func TestIssue32213(t *testing.T) {
+	store, clean := testkit.CreateMockStore(t)
+	defer clean()
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec(`use test`)
+
+	tk.MustExec("create table test.t1(c1 float)")
+	tk.MustExec("insert into test.t1 values(999.99)")
+	tk.MustQuery("select cast(test.t1.c1 as decimal(4, 1)) from test.t1").Check(testkit.Rows("999.9"))
+	tk.MustQuery("select cast(test.t1.c1 as decimal(5, 1)) from test.t1").Check(testkit.Rows("1000.0"))
+
+	tk.MustExec("drop table if exists test.t1")
+	tk.MustExec("create table test.t1(c1 decimal(6, 4))")
+	tk.MustExec("insert into test.t1 values(99.9999)")
+	tk.MustQuery("select cast(test.t1.c1 as decimal(5, 3)) from test.t1").Check(testkit.Rows("99.999"))
+	tk.MustQuery("select cast(test.t1.c1 as decimal(6, 3)) from test.t1").Check(testkit.Rows("100.000"))
+}

expression/aggregation/avg.go

@@ -86,7 +86,7 @@ func (af *avgFunction) GetResult(evalCtx *AggEvaluateContext) (d types.Datum) {
 		if frac == -1 {
 			frac = mysql.MaxDecimalScale
 		}
-		err = to.Round(to, mathutil.Min(frac, mysql.MaxDecimalScale), types.ModeHalfEven)
+		err = to.Round(to, mathutil.Min(frac, mysql.MaxDecimalScale), types.ModeHalfUp)
 		terror.Log(err)
 		d.SetMysqlDecimal(to)
 	}

expression/builtin_arithmetic.go

@@ -726,7 +726,7 @@ func (s *builtinArithmeticDivideDecimalSig) evalDecimal(row chunk.Row) (*types.M
 	} else if err == nil {
 		_, frac := c.PrecisionAndFrac()
 		if frac < s.baseBuiltinFunc.tp.Decimal {
-			err = c.Round(c, s.baseBuiltinFunc.tp.Decimal, types.ModeHalfEven)
+			err = c.Round(c, s.baseBuiltinFunc.tp.Decimal, types.ModeHalfUp)
 		}
 	} else if err == types.ErrOverflow {
 		err = types.ErrOverflow.GenWithStackByArgs("DECIMAL", fmt.Sprintf("(%s / %s)", s.args[0].String(), s.args[1].String()))

expression/builtin_arithmetic_vec.go

@@ -100,7 +100,7 @@ func (b *builtinArithmeticDivideDecimalSig) vecEvalDecimal(input *chunk.Chunk, r
 		} else if err == nil {
 			_, frac = to.PrecisionAndFrac()
 			if frac < b.baseBuiltinFunc.tp.Decimal {
-				if err = to.Round(&to, b.baseBuiltinFunc.tp.Decimal, types.ModeHalfEven); err != nil {
+				if err = to.Round(&to, b.baseBuiltinFunc.tp.Decimal, types.ModeHalfUp); err != nil {
 					return err
 				}
 			}

expression/builtin_cast.go

@@ -969,7 +969,7 @@ func (b *builtinCastDecimalAsIntSig) evalInt(row chunk.Row) (res int64, isNull b
 
 	// Round is needed for both unsigned and signed.
 	var to types.MyDecimal
-	err = val.Round(&to, 0, types.ModeHalfEven)
+	err = val.Round(&to, 0, types.ModeHalfUp)
 	if err != nil {
 		return 0, true, err
 	}

expression/builtin_cast_vec.go

@@ -1743,7 +1743,7 @@ func (b *builtinCastDecimalAsIntSig) vecEvalInt(input *chunk.Chunk, result *chun
 
 		// Round is needed for both unsigned and signed.
 		to := d64s[i]
-		err = d64s[i].Round(&to, 0, types.ModeHalfEven)
+		err = d64s[i].Round(&to, 0, types.ModeHalfUp)
 		if err != nil {
 			return err
 		}

expression/builtin_math.go

@@ -393,7 +393,7 @@ func (b *builtinRoundDecSig) evalDecimal(row chunk.Row) (*types.MyDecimal, bool,
 		return nil, isNull, err
 	}
 	to := new(types.MyDecimal)
-	if err = val.Round(to, 0, types.ModeHalfEven); err != nil {
+	if err = val.Round(to, 0, types.ModeHalfUp); err != nil {
 		return nil, true, err
 	}
 	return to, false, nil
@@ -469,7 +469,7 @@ func (b *builtinRoundWithFracDecSig) evalDecimal(row chunk.Row) (*types.MyDecima
 		return nil, isNull, err
 	}
 	to := new(types.MyDecimal)
-	if err = val.Round(to, mathutil.Min(int(frac), b.tp.Decimal), types.ModeHalfEven); err != nil {
+	if err = val.Round(to, mathutil.Min(int(frac), b.tp.Decimal), types.ModeHalfUp); err != nil {
 		return nil, true, err
 	}
 	return to, false, nil

expression/builtin_math_vec.go

@@ -392,7 +392,7 @@ func (b *builtinRoundDecSig) vecEvalDecimal(input *chunk.Chunk, result *chunk.Co
 		if result.IsNull(i) {
 			continue
 		}
-		if err := d64s[i].Round(buf, 0, types.ModeHalfEven); err != nil {
+		if err := d64s[i].Round(buf, 0, types.ModeHalfUp); err != nil {
 			return err
 		}
 		d64s[i] = *buf
@@ -994,7 +994,7 @@ func (b *builtinRoundWithFracDecSig) vecEvalDecimal(input *chunk.Chunk, result *
 			continue
 		}
 		// TODO: reuse d64[i] and remove the temporary variable tmp.
-		if err := d64s[i].Round(tmp, mathutil.Min(int(i64s[i]), b.tp.Decimal), types.ModeHalfEven); err != nil {
+		if err := d64s[i].Round(tmp, mathutil.Min(int(i64s[i]), b.tp.Decimal), types.ModeHalfUp); err != nil {
 			return err
 		}
 		d64s[i] = *tmp

expression/builtin_time.go

@@ -1734,7 +1734,7 @@ func evalFromUnixTime(ctx sessionctx.Context, fsp int, unixTimeStamp *types.MyDe
 
 	sc := ctx.GetSessionVars().StmtCtx
 	tmp := time.Unix(integralPart, fractionalPart).In(sc.TimeZone)
-	t, err := convertTimeToMysqlTime(tmp, fsp, types.ModeHalfEven)
+	t, err := convertTimeToMysqlTime(tmp, fsp, types.ModeHalfUp)
 	if err != nil {
 		return res, true, err
 	}
@@ -2050,7 +2050,7 @@ func (b *builtinSysDateWithFspSig) evalTime(row chunk.Row) (d types.Time, isNull
 
 	loc := b.ctx.GetSessionVars().Location()
 	now := time.Now().In(loc)
-	result, err := convertTimeToMysqlTime(now, int(fsp), types.ModeHalfEven)
+	result, err := convertTimeToMysqlTime(now, int(fsp), types.ModeHalfUp)
 	if err != nil {
 		return types.ZeroTime, true, err
 	}
@@ -2072,7 +2072,7 @@ func (b *builtinSysDateWithoutFspSig) Clone() builtinFunc {
 func (b *builtinSysDateWithoutFspSig) evalTime(row chunk.Row) (d types.Time, isNull bool, err error) {
 	tz := b.ctx.GetSessionVars().Location()
 	now := time.Now().In(tz)
-	result, err := convertTimeToMysqlTime(now, 0, types.ModeHalfEven)
+	result, err := convertTimeToMysqlTime(now, 0, types.ModeHalfUp)
 	if err != nil {
 		return types.ZeroTime, true, err
 	}
@@ -2393,7 +2393,7 @@ func evalUTCTimestampWithFsp(ctx sessionctx.Context, fsp int) (types.Time, bool,
 	if err != nil {
 		return types.ZeroTime, true, err
 	}
-	result, err := convertTimeToMysqlTime(nowTs.UTC(), fsp, types.ModeHalfEven)
+	result, err := convertTimeToMysqlTime(nowTs.UTC(), fsp, types.ModeHalfUp)
 	if err != nil {
 		return types.ZeroTime, true, err
 	}

expression/builtin_time_vec.go

@@ -172,7 +172,7 @@ func (b *builtinSysDateWithoutFspSig) vecEvalTime(input *chunk.Chunk, result *ch
 
 	result.ResizeTime(n, false)
 	times := result.Times()
-	t, err := convertTimeToMysqlTime(now, 0, types.ModeHalfEven)
+	t, err := convertTimeToMysqlTime(now, 0, types.ModeHalfUp)
 	if err != nil {
 		return err
 	}
@@ -775,7 +775,7 @@ func (b *builtinSysDateWithFspSig) vecEvalTime(input *chunk.Chunk, result *chunk
 		if result.IsNull(i) {
 			continue
 		}
-		t, err := convertTimeToMysqlTime(now, int(ds[i]), types.ModeHalfEven)
+		t, err := convertTimeToMysqlTime(now, int(ds[i]), types.ModeHalfUp)
 		if err != nil {
 			return err
 		}

expression/constant.go

@@ -295,7 +295,7 @@ func (c *Constant) EvalDecimal(ctx sessionctx.Context, row chunk.Row) (*types.My
 	// The decimal may be modified during plan building.
 	_, frac := res.PrecisionAndFrac()
 	if frac < c.GetType().Decimal {
-		err = res.Round(res, c.GetType().Decimal, types.ModeHalfEven)
+		err = res.Round(res, c.GetType().Decimal, types.ModeHalfUp)
 	}
 	return res, false, err
 }

types/convert_test.go

@@ -841,7 +841,7 @@ func TestConvert(t *testing.T) {
 	dec := NewDecFromInt(-123)
 	err := dec.Shift(-5)
 	require.NoError(t, err)
-	err = dec.Round(dec, 5, ModeHalfEven)
+	err = dec.Round(dec, 5, ModeHalfUp)
 	require.NoError(t, err)
 	signedAccept(t, mysql.TypeNewDecimal, dec, "-0.00123")
 }

types/datum.go

@@ -1141,7 +1141,7 @@ func (d *Datum) convertToUint(sc *stmtctx.StatementContext, target *FieldType) (
 		}
 	case KindMysqlTime:
 		dec := d.GetMysqlTime().ToNumber()
-		err = dec.Round(dec, 0, ModeHalfEven)
+		err = dec.Round(dec, 0, ModeHalfUp)
 		ival, err1 := dec.ToInt()
 		if err == nil {
 			err = err1
@@ -1152,7 +1152,7 @@ func (d *Datum) convertToUint(sc *stmtctx.StatementContext, target *FieldType) (
 		}
 	case KindMysqlDuration:
 		dec := d.GetMysqlDuration().ToNumber()
-		err = dec.Round(dec, 0, ModeHalfEven)
+		err = dec.Round(dec, 0, ModeHalfUp)
 		ival, err1 := dec.ToInt()
 		if err1 == nil {
 			val, err = ConvertIntToUint(sc, ival, upperBound, tp)
@@ -1429,20 +1429,27 @@ func ProduceDecWithSpecifiedTp(dec *MyDecimal, tp *FieldType, sc *stmtctx.Statem
 		if flen < decimal {
 			return nil, ErrMBiggerThanD.GenWithStackByArgs("")
 		}
-		prec, frac := dec.PrecisionAndFrac()
-		if !dec.IsZero() && prec-frac > flen-decimal {
-			dec = NewMaxOrMinDec(dec.IsNegative(), flen, decimal)
-			// select (cast 111 as decimal(1)) causes a warning in MySQL.
-			err = ErrOverflow.GenWithStackByArgs("DECIMAL", fmt.Sprintf("(%d, %d)", flen, decimal))
-		} else if frac != decimal {
-			old := *dec
-			err = dec.Round(dec, decimal, ModeHalfEven)
-			if err != nil {
-				return nil, err
-			}
-			if !old.IsZero() && frac > decimal && dec.Compare(&old) != 0 {
-				sc.AppendWarning(ErrTruncatedWrongVal.GenWithStackByArgs("DECIMAL", &old))
-				err = nil
+
+		var old *MyDecimal
+		isZero := dec.IsZero()
+
+		if !isZero && int(dec.digitsFrac) > decimal {
+			old = new(MyDecimal)
+			*old = *dec
+		}
+		err = dec.Round(dec, decimal, ModeHalfUp)
+		if err != nil {
+			return nil, err
+		}
+
+		if !isZero {
+			_, digitsInt := dec.removeLeadingZeros()
+			if flen-decimal < digitsInt {
+				dec = NewMaxOrMinDec(dec.IsNegative(), flen, decimal)
+				// select cast(111 as decimal(1)) causes a warning in MySQL.
+				err = ErrOverflow.GenWithStackByArgs("DECIMAL", fmt.Sprintf("(%d, %d)", flen, decimal))
+			} else if old != nil && dec.Compare(old) != 0 {
+				sc.AppendWarning(ErrTruncatedWrongVal.GenWithStackByArgs("DECIMAL", old))
 			}
 		}
 	}
@@ -1806,7 +1813,7 @@ func (d *Datum) toSignedInteger(sc *stmtctx.StatementContext, tp byte) (int64, e
 		return ival, errors.Trace(err)
 	case KindMysqlDecimal:
 		var to MyDecimal
-		err := d.GetMysqlDecimal().Round(&to, 0, ModeHalfEven)
+		err := d.GetMysqlDecimal().Round(&to, 0, ModeHalfUp)
 		ival, err1 := to.ToInt()
 		if err == nil {
 			err = err1

types/datum_test.go

@@ -27,6 +27,7 @@ import (
 	"github.com/pingcap/tidb/types/json"
 	"github.com/pingcap/tidb/util/collate"
 	"github.com/pingcap/tidb/util/hack"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -566,3 +567,49 @@ func BenchmarkCompareDatumByReflect(b *testing.B) {
 		reflect.DeepEqual(vals, vals1)
 	}
 }
+
+func TestProduceDecWithSpecifiedTp(t *testing.T) {
+	tests := []struct {
+		dec        string
+		flen       int
+		frac       int
+		newDec     string
+		isOverflow bool
+	}{
+		{"0.0000", 4, 3, "0.000", false},
+		{"0.0001", 4, 3, "0.000", false},
+		{"123", 8, 5, "123.00000", false},
+		{"-123", 8, 5, "-123.00000", false},
+		{"123.899", 5, 2, "123.90", false},
+		{"-123.899", 5, 2, "-123.90", false},
+		{"123.899", 6, 2, "123.90", false},
+		{"-123.899", 6, 2, "-123.90", false},
+		{"123.99", 4, 1, "124.0", false},
+		{"123.99", 3, 0, "124", false},
+		{"-123.99", 3, 0, "-124", false},
+		{"123.99", 3, 1, "99.9", true},
+		{"-123.99", 3, 1, "-99.9", true},
+		{"99.9999", 5, 3, "99.999", true},
+		{"-99.9999", 5, 3, "-99.999", true},
+		{"99.9999", 6, 3, "100.000", false},
+		{"-99.9999", 6, 3, "-100.000", false},
+	}
+	sc := new(stmtctx.StatementContext)
+	for _, tt := range tests {
+		tp := &FieldType{
+			Tp:      mysql.TypeNewDecimal,
+			Flen:    tt.flen,
+			Decimal: tt.frac,
+		}
+		dec := NewDecFromStringForTest(tt.dec)
+		newDec, err := ProduceDecWithSpecifiedTp(dec, tp, sc)
+		if tt.isOverflow {
+			if !ErrOverflow.Equal(err) {
+				assert.FailNow(t, "Error is not overflow", err)
+			}
+		} else {
+			require.NoError(t, err, tt)
+		}
+		require.Equal(t, tt.newDec, newDec.String())
+	}
+}