cherry pick pingcap#36500 to release-5.3

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>

executor/write_test.go

@@ -2106,7 +2106,29 @@ func (s *testSuite4) TestIssue18681(c *C) {
 	c.Assert(sc.WarningCount(), Equals, uint16(0))
 }
 
+<<<<<<< HEAD
 func (s *testSuite4) TestLoadData(c *C) {
+=======
+func TestIssue33298(t *testing.T) {
+	store, clean := testkit.CreateMockStore(t)
+	defer clean()
+	tk := testkit.NewTestKit(t, store)
+	ctx := tk.Session().(sessionctx.Context)
+	defer ctx.SetValue(executor.LoadDataVarKey, nil)
+
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists load_data_test")
+	tk.MustExec("create table load_data_test (a varchar(10), b varchar(10))")
+
+	// According to https://dev.mysql.com/doc/refman/8.0/en/load-data.html , fixed-row format should be used when fields
+	// terminated by '' and enclosed by ''. However, tidb doesn't support it yet and empty terminator leads to infinite
+	// loop in `indexOfTerminator` (see https://github.com/pingcap/tidb/issues/33298).
+	require.Error(t, tk.ExecToErr("load data local infile '/tmp/nonexistence.csv' into table load_data_test fields terminated by ''"))
+	require.Error(t, tk.ExecToErr("load data local infile '/tmp/nonexistence.csv' into table load_data_test fields terminated by '' enclosed by ''"))
+}
+
+func TestLoadData(t *testing.T) {
+>>>>>>> bce690170... planner: forbid load data with empty field terminator (#36500)
 	trivialMsg := "Records: 1  Deleted: 0  Skipped: 0  Warnings: 0"
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")

planner/core/planbuilder.go

@@ -3476,6 +3476,10 @@ func (b *PlanBuilder) buildSelectPlanOfInsert(ctx context.Context, insert *ast.I
 }
 
 func (b *PlanBuilder) buildLoadData(ctx context.Context, ld *ast.LoadDataStmt) (Plan, error) {
+	// quick fix for https://github.com/pingcap/tidb/issues/33298
+	if ld.FieldsInfo != nil && len(ld.FieldsInfo.Terminated) == 0 {
+		return nil, ErrNotSupportedYet.GenWithStackByArgs("load data with empty field terminator")
+	}
 	p := LoadData{
 		IsLocal:            ld.IsLocal,
 		OnDuplicate:        ld.OnDuplicate,