expression: handle max allowed packet for cast_as_binary

expression/builtin_cast.go

@@ -33,6 +33,7 @@ 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"
@@ -268,7 +269,12 @@ func (c *castAsStringFunctionClass) getFunction(ctx sessionctx.Context, args []E
 	bf := newBaseBuiltinFunc(ctx, args)
 	bf.tp = c.tp
 	if args[0].GetType().Hybrid() || IsBinaryLiteral(args[0]) {
-		sig = &builtinCastStringAsStringSig{bf}
+		valStr, _ := ctx.GetSessionVars().GetSystemVar(variable.MaxAllowedPacket)
+		maxAllowedPacket, err := strconv.ParseUint(valStr, 10, 64)
+		if err != nil {
+			return nil, errors.Trace(err)
+		}
+		sig = &builtinCastStringAsStringSig{bf, maxAllowedPacket}
 		sig.setPbCode(tipb.ScalarFuncSig_CastStringAsString)
 		return sig, nil
 	}
@@ -293,7 +299,12 @@ func (c *castAsStringFunctionClass) getFunction(ctx sessionctx.Context, args []E
 		sig = &builtinCastJSONAsStringSig{bf}
 		sig.setPbCode(tipb.ScalarFuncSig_CastJsonAsString)
 	case types.ETString:
-		sig = &builtinCastStringAsStringSig{bf}
+		valStr, _ := ctx.GetSessionVars().GetSystemVar(variable.MaxAllowedPacket)
+		maxAllowedPacket, err := strconv.ParseUint(valStr, 10, 64)
+		if err != nil {
+			return nil, errors.Trace(err)
+		}
+		sig = &builtinCastStringAsStringSig{bf, maxAllowedPacket}
 		sig.setPbCode(tipb.ScalarFuncSig_CastStringAsString)
 	default:
 		panic("unsupported types.EvalType in castAsStringFunctionClass")
@@ -1007,11 +1018,13 @@ func (b *builtinCastDecimalAsDurationSig) evalDuration(row chunk.Row) (res types
 
 type builtinCastStringAsStringSig struct {
 	baseBuiltinFunc
+	maxAllowedPacket uint64
 }
 
 func (b *builtinCastStringAsStringSig) Clone() builtinFunc {
 	newSig := &builtinCastStringAsStringSig{}
 	newSig.cloneFrom(&b.baseBuiltinFunc)
+	newSig.maxAllowedPacket = b.maxAllowedPacket
 	return newSig
 }
 
@@ -1021,6 +1034,13 @@ func (b *builtinCastStringAsStringSig) evalString(row chunk.Row) (res string, is
 		return res, isNull, errors.Trace(err)
 	}
 	sc := b.ctx.GetSessionVars().StmtCtx
+
+	isTooLarge := uint64(len(res)) > b.maxAllowedPacket || (b.tp.Flen != types.UnspecifiedLength && uint64(b.tp.Flen) > b.maxAllowedPacket)
+	if types.IsBinaryStr(b.tp) && isTooLarge {
+		b.ctx.GetSessionVars().StmtCtx.AppendWarning(errWarnAllowedPacketOverflowed.GenWithStackByArgs("cast_as_binary", b.maxAllowedPacket))
+		return "", true, nil
+	}
+
 	res, err = types.ProduceStrWithSpecifiedTp(res, b.tp, sc)
 	return res, false, errors.Trace(err)
 }

expression/builtin_cast_test.go

@@ -654,7 +654,7 @@ func (s *testEvaluatorSuite) TestCastFuncSig(c *C) {
 		case 5:
 			sig = &builtinCastJSONAsStringSig{stringFunc}
 		case 6:
-			sig = &builtinCastStringAsStringSig{stringFunc}
+			sig = &builtinCastStringAsStringSig{stringFunc, 1 << 20}
 		}
 		res, isNull, err := sig.evalString(t.row.ToRow())
 		c.Assert(isNull, Equals, false)
@@ -731,7 +731,7 @@ func (s *testEvaluatorSuite) TestCastFuncSig(c *C) {
 			sig = &builtinCastDurationAsStringSig{stringFunc}
 		case 5:
 			stringFunc.tp.Charset = charset.CharsetUTF8
-			sig = &builtinCastStringAsStringSig{stringFunc}
+			sig = &builtinCastStringAsStringSig{stringFunc, 1 << 20}
 		}
 		res, isNull, err := sig.evalString(t.row.ToRow())
 		c.Assert(isNull, Equals, false)

expression/builtin_time_test.go

@@ -14,7 +14,6 @@
 package expression
 
 import (
-	"fmt"
 	"math"
 	"strings"
 	"time"
@@ -1615,7 +1614,6 @@ func (s *testEvaluatorSuite) TestUnixTimestamp(c *C) {
 	}
 
 	for _, test := range tests {
-		fmt.Printf("Begin Test %v\n", test)
 		expr := s.datumsToConstants([]types.Datum{test.input})
 		expr[0].GetType().Decimal = test.inputDecimal
 		resetStmtContext(s.ctx)

expression/distsql_builtin.go

@@ -15,13 +15,15 @@ package expression
 
 import (
 	"fmt"
+	"strconv"
 	"time"
 
 	"github.com/pingcap/errors"
 	"github.com/pingcap/parser/model"
 	"github.com/pingcap/parser/mysql"
 	"github.com/pingcap/tidb/sessionctx"
 	"github.com/pingcap/tidb/sessionctx/stmtctx"
+	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/codec"
 	"github.com/pingcap/tidb/util/mock"
@@ -115,7 +117,12 @@ func getSignatureByPB(ctx sessionctx.Context, sigCode tipb.ScalarFuncSig, tp *ti
 	case tipb.ScalarFuncSig_CastTimeAsString:
 		f = &builtinCastTimeAsStringSig{base}
 	case tipb.ScalarFuncSig_CastStringAsString:
-		f = &builtinCastStringAsStringSig{base}
+		valStr, _ := ctx.GetSessionVars().GetSystemVar(variable.MaxAllowedPacket)
+		maxAllowedPacket, err := strconv.ParseUint(valStr, 10, 64)
+		if err != nil {
+			return nil, errors.Trace(err)
+		}
+		f = &builtinCastStringAsStringSig{base, maxAllowedPacket}
 	case tipb.ScalarFuncSig_CastJsonAsString:
 		f = &builtinCastJSONAsStringSig{base}
 

expression/integration_test.go

@@ -936,6 +936,9 @@ func (s *testIntegrationSuite) TestStringBuiltin(c *C) {
 	result = tk.MustQuery("select a,b,concat_ws(',',a,b) from t")
 	result.Check(testkit.Rows("114.57011441 38.04620115 114.57011441,38.04620115",
 		"-38.04620119 38.04620115 -38.04620119,38.04620115"))
+
+	result = tk.MustQuery("SELECT CAST('a' AS BINARY(67108865));")
+	result.Check(testkit.Rows("<nil>"))
 }
 
 func (s *testIntegrationSuite) TestEncryptionBuiltin(c *C) {

session/session.go

@@ -1056,6 +1056,7 @@ func CreateSession4Test(store kv.Storage) (Session, error) {
 	if err == nil {
 		// initialize session variables for test.
 		s.GetSessionVars().MaxChunkSize = 2
+		s.GetSessionVars().SetSystemVar(variable.MaxAllowedPacket, variable.SysVars[variable.MaxAllowedPacket].Value)
 	}
 	return s, errors.Trace(err)
 }

sessionctx/variable/session.go

@@ -378,6 +378,7 @@ func NewSessionVars() *SessionVars {
 		enableStreaming = "0"
 	}
 	terror.Log(vars.SetSystemVar(TiDBEnableStreaming, enableStreaming))
+	terror.Log(vars.SetSystemVar(MaxAllowedPacket, SysVars[MaxAllowedPacket].Value))
 	return vars
 }