expression: fix wrong retType for reverse function (#30829)

close #30809
pingcap · Dec 21, 2021 · f1e5877 · f1e5877
1 parent cbe7492
commit f1e5877
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Showing 4 changed files with 27 additions and 6 deletions.
diff --git a/cmd/explaintest/r/explain_generate_column_substitute.result b/cmd/explaintest/r/explain_generate_column_substitute.result
@@ -570,3 +570,10 @@ a
 select * from t004 ignore index (eidx) where timestampadd(microsecond, 1, a) = timestampadd(microsecond, 1, '2021-08-20');
 a
 2021-08-20
+drop table if exists t;
+create table t ( c_int int, c_str varchar(40) character set utf8 collate utf8_general_ci, primary key(c_int, c_str(9))  clustered, key idx((reverse(c_str))));
+replace into t (c_int, c_str) values (9, "beautiful hermann");
+select reverse(c_str) from t use index(idx);
+reverse(c_str)
+nnamreh lufituaeb
+drop table t;
diff --git a/cmd/explaintest/t/explain_generate_column_substitute.test b/cmd/explaintest/t/explain_generate_column_substitute.test
@@ -259,3 +259,10 @@ select * from t004 where timestampadd(microsecond, 1, a) = timestampadd(microsec
 alter table t004 add index eidx ((timestampadd(microsecond, 1, a)));
 select * from t004 use index(eidx) where timestampadd(microsecond, 1, a) = timestampadd(microsecond, 1, '2021-08-20');
 select * from t004 ignore index (eidx) where timestampadd(microsecond, 1, a) = timestampadd(microsecond, 1, '2021-08-20');
+
+drop table if exists t;
+create table t ( c_int int, c_str varchar(40) character set utf8 collate utf8_general_ci, primary key(c_int, c_str(9))  clustered, key idx((reverse(c_str))));
+replace into t (c_int, c_str) values (9, "beautiful hermann");
+select reverse(c_str) from t use index(idx);
+
+drop table t;
diff --git a/ddl/ddl_api.go b/ddl/ddl_api.go
@@ -5360,6 +5360,11 @@ func buildHiddenColumnInfo(ctx sessionctx.Context, indexPartSpecifications []*as
 			Hidden:              true,
 			FieldType:           *expr.GetType(),
 		}
+		// Reset some flag, it may be caused by wrong type infer. But it's not easy to fix them all, so reset them here for safety.
+		colInfo.Flag &= ^mysql.PriKeyFlag
+		colInfo.Flag &= ^mysql.UniqueKeyFlag
+		colInfo.Flag &= ^mysql.AutoIncrementFlag
+
 		if colInfo.Tp == mysql.TypeDatetime || colInfo.Tp == mysql.TypeDate || colInfo.Tp == mysql.TypeTimestamp || colInfo.Tp == mysql.TypeDuration {
 			if colInfo.FieldType.Decimal == types.UnspecifiedLength {
 				colInfo.FieldType.Decimal = int(types.MaxFsp)

diff --git a/expression/builtin_string.go b/expression/builtin_string.go
@@ -173,10 +173,12 @@ func reverseRunes(origin []rune) []rune {
 
 // SetBinFlagOrBinStr sets resTp to binary string if argTp is a binary string,
 // if not, sets the binary flag of resTp to true if argTp has binary flag.
+// We need to check if the tp is enum or set, if so, don't add binary flag directly unless it has binary flag.
 func SetBinFlagOrBinStr(argTp *types.FieldType, resTp *types.FieldType) {
+	nonEnumOrSet := !(argTp.Tp == mysql.TypeEnum || argTp.Tp == mysql.TypeSet)
 	if types.IsBinaryStr(argTp) {
 		types.SetBinChsClnFlag(resTp)
-	} else if mysql.HasBinaryFlag(argTp.Flag) || !types.IsNonBinaryStr(argTp) {
+	} else if mysql.HasBinaryFlag(argTp.Flag) || (!types.IsNonBinaryStr(argTp) && nonEnumOrSet) {
 		resTp.Flag |= mysql.BinaryFlag
 	}
 }
@@ -765,12 +767,12 @@ func (c *reverseFunctionClass) getFunction(ctx sessionctx.Context, args []Expres
 	if err != nil {
 		return nil, err
 	}
-	retTp := *args[0].GetType()
-	retTp.Tp = mysql.TypeVarString
-	retTp.Decimal = types.UnspecifiedLength
-	bf.tp = &retTp
+
+	argTp := args[0].GetType()
+	bf.tp.Flen = args[0].GetType().Flen
+	addBinFlag(bf.tp)
 	var sig builtinFunc
-	if types.IsBinaryStr(bf.tp) {
+	if types.IsBinaryStr(argTp) {
 		sig = &builtinReverseSig{bf}
 		sig.setPbCode(tipb.ScalarFuncSig_Reverse)
 	} else {