expression: return null when cast to huge binary type (pingcap#8768)

expression/builtin_cast.go

@@ -32,6 +32,7 @@ import (
 	"github.com/pingcap/parser/mysql"
 	"github.com/pingcap/parser/terror"
 	"github.com/pingcap/tidb/sessionctx"
+	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/types/json"
 	"github.com/pingcap/tidb/util/chunk"
@@ -525,8 +526,11 @@ func (b *builtinCastIntAsStringSig) evalString(row chunk.Row) (res string, isNul
 		}
 		res = strconv.FormatUint(uVal, 10)
 	}
-	res, err = types.ProduceStrWithSpecifiedTp(res, b.tp, b.ctx.GetSessionVars().StmtCtx)
-	return res, false, err
+	res, err = types.ProduceStrWithSpecifiedTp(res, b.tp, b.ctx.GetSessionVars().StmtCtx, false)
+	if err != nil {
+		return res, false, err
+	}
+	return padZeroForBinaryType(res, b.tp, b.ctx)
 }
 
 type builtinCastIntAsTimeSig struct {
@@ -793,8 +797,11 @@ func (b *builtinCastRealAsStringSig) evalString(row chunk.Row) (res string, isNu
 	if isNull || err != nil {
 		return res, isNull, err
 	}
-	res, err = types.ProduceStrWithSpecifiedTp(strconv.FormatFloat(val, 'f', -1, 64), b.tp, b.ctx.GetSessionVars().StmtCtx)
-	return res, isNull, err
+	res, err = types.ProduceStrWithSpecifiedTp(strconv.FormatFloat(val, 'f', -1, 64), b.tp, b.ctx.GetSessionVars().StmtCtx, false)
+	if err != nil {
+		return res, false, err
+	}
+	return padZeroForBinaryType(res, b.tp, b.ctx)
 }
 
 type builtinCastRealAsTimeSig struct {
@@ -924,8 +931,11 @@ func (b *builtinCastDecimalAsStringSig) evalString(row chunk.Row) (res string, i
 		return res, isNull, err
 	}
 	sc := b.ctx.GetSessionVars().StmtCtx
-	res, err = types.ProduceStrWithSpecifiedTp(string(val.ToString()), b.tp, sc)
-	return res, false, err
+	res, err = types.ProduceStrWithSpecifiedTp(string(val.ToString()), b.tp, sc, false)
+	if err != nil {
+		return res, false, err
+	}
+	return padZeroForBinaryType(res, b.tp, b.ctx)
 }
 
 type builtinCastDecimalAsRealSig struct {
@@ -1020,8 +1030,11 @@ func (b *builtinCastStringAsStringSig) evalString(row chunk.Row) (res string, is
 		return res, isNull, err
 	}
 	sc := b.ctx.GetSessionVars().StmtCtx
-	res, err = types.ProduceStrWithSpecifiedTp(res, b.tp, sc)
-	return res, false, err
+	res, err = types.ProduceStrWithSpecifiedTp(res, b.tp, sc, false)
+	if err != nil {
+		return res, false, err
+	}
+	return padZeroForBinaryType(res, b.tp, b.ctx)
 }
 
 type builtinCastStringAsIntSig struct {
@@ -1318,8 +1331,11 @@ func (b *builtinCastTimeAsStringSig) evalString(row chunk.Row) (res string, isNu
 		return res, isNull, err
 	}
 	sc := b.ctx.GetSessionVars().StmtCtx
-	res, err = types.ProduceStrWithSpecifiedTp(val.String(), b.tp, sc)
-	return res, false, err
+	res, err = types.ProduceStrWithSpecifiedTp(val.String(), b.tp, sc, false)
+	if err != nil {
+		return res, false, err
+	}
+	return padZeroForBinaryType(res, b.tp, b.ctx)
 }
 
 type builtinCastTimeAsDurationSig struct {
@@ -1442,8 +1458,30 @@ func (b *builtinCastDurationAsStringSig) evalString(row chunk.Row) (res string,
 		return res, isNull, err
 	}
 	sc := b.ctx.GetSessionVars().StmtCtx
-	res, err = types.ProduceStrWithSpecifiedTp(val.String(), b.tp, sc)
-	return res, false, err
+	res, err = types.ProduceStrWithSpecifiedTp(val.String(), b.tp, sc, false)
+	if err != nil {
+		return res, false, err
+	}
+	return padZeroForBinaryType(res, b.tp, b.ctx)
+}
+
+func padZeroForBinaryType(s string, tp *types.FieldType, ctx sessionctx.Context) (string, bool, error) {
+	flen := tp.Flen
+	if tp.Tp == mysql.TypeString && types.IsBinaryStr(tp) && len(s) < flen {
+		sc := ctx.GetSessionVars().StmtCtx
+		valStr, _ := ctx.GetSessionVars().GetSystemVar(variable.MaxAllowedPacket)
+		maxAllowedPacket, err := strconv.ParseUint(valStr, 10, 64)
+		if err != nil {
+			return "", false, err
+		}
+		if uint64(flen) > maxAllowedPacket {
+			sc.AppendWarning(errWarnAllowedPacketOverflowed.GenWithStackByArgs("cast_as_binary", maxAllowedPacket))
+			return "", true, nil
+		}
+		padding := make([]byte, flen-len(s))
+		s = string(append([]byte(s), padding...))
+	}
+	return s, false, nil
 }
 
 type builtinCastDurationAsTimeSig struct {

expression/builtin_cast_test.go

@@ -76,6 +76,17 @@ func (s *testEvaluatorSuite) TestCast(c *C) {
 	c.Assert(len(res.GetString()), Equals, 5)
 	c.Assert(res.GetString(), Equals, string([]byte{'a', 0x00, 0x00, 0x00, 0x00}))
 
+	// cast(str as binary(N)), N > len([]byte(str)).
+	// cast("a" as binary(4294967295))
+	tp.Flen = 4294967295
+	f = BuildCastFunction(ctx, &Constant{Value: types.NewDatum("a"), RetType: types.NewFieldType(mysql.TypeString)}, tp)
+	res, err = f.Eval(chunk.Row{})
+	c.Assert(err, IsNil)
+	c.Assert(res.IsNull(), IsTrue)
+	warnings := sc.GetWarnings()
+	lastWarn := warnings[len(warnings)-1]
+	c.Assert(terror.ErrorEqual(errWarnAllowedPacketOverflowed, lastWarn.Err), IsTrue, Commentf("err %v", lastWarn.Err))
+
 	origSc := sc
 	sc.InSelectStmt = true
 	sc.OverflowAsWarning = true
@@ -93,8 +104,8 @@ func (s *testEvaluatorSuite) TestCast(c *C) {
 	c.Assert(err, IsNil)
 	c.Assert(res.GetUint64() == math.MaxUint64, IsTrue)
 
-	warnings := sc.GetWarnings()
-	lastWarn := warnings[len(warnings)-1]
+	warnings = sc.GetWarnings()
+	lastWarn = warnings[len(warnings)-1]
 	c.Assert(terror.ErrorEqual(types.ErrTruncatedWrongVal, lastWarn.Err), IsTrue, Commentf("err %v", lastWarn.Err))
 
 	originFlag := tp1.Flag

types/datum.go

@@ -804,16 +804,17 @@ func (d *Datum) convertToString(sc *stmtctx.StatementContext, target *FieldType)
 	default:
 		return invalidConv(d, target.Tp)
 	}
-	s, err := ProduceStrWithSpecifiedTp(s, target, sc)
+	s, err := ProduceStrWithSpecifiedTp(s, target, sc, true)
 	ret.SetString(s)
 	if target.Charset == charset.CharsetBin {
 		ret.k = KindBytes
 	}
 	return ret, errors.Trace(err)
 }
 
-// ProduceStrWithSpecifiedTp produces a new string according to `flen` and `chs`.
-func ProduceStrWithSpecifiedTp(s string, tp *FieldType, sc *stmtctx.StatementContext) (_ string, err error) {
+// ProduceStrWithSpecifiedTp produces a new string according to `flen` and `chs`. Param `padZero` indicates
+// whether we should pad `\0` for `binary(flen)` type.
+func ProduceStrWithSpecifiedTp(s string, tp *FieldType, sc *stmtctx.StatementContext, padZero bool) (_ string, err error) {
 	flen, chs := tp.Flen, tp.Charset
 	if flen >= 0 {
 		// Flen is the rune length, not binary length, for UTF8 charset, we need to calculate the
@@ -842,7 +843,7 @@ func ProduceStrWithSpecifiedTp(s string, tp *FieldType, sc *stmtctx.StatementCon
 		} else if len(s) > flen {
 			err = ErrDataTooLong.GenWithStack("Data Too Long, field len %d, data len %d", flen, len(s))
 			s = truncateStr(s, flen)
-		} else if tp.Tp == mysql.TypeString && IsBinaryStr(tp) && len(s) < flen {
+		} else if tp.Tp == mysql.TypeString && IsBinaryStr(tp) && len(s) < flen && padZero {
 			padding := make([]byte, flen-len(s))
 			s = string(append([]byte(s), padding...))
 		}