cherry pick pingcap#20924 to release-4.0

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

server/conn.go

@@ -1251,7 +1251,9 @@ func (cc *clientConn) handleLoadData(ctx context.Context, loadDataInfo *executor
 	if loadDataInfo == nil {
 		return errors.New("load data info is empty")
 	}
-
+	if !loadDataInfo.Table.Meta().IsBaseTable() {
+		return errors.New("can only load data into base tables")
+	}
 	err := cc.writeReq(ctx, loadDataInfo.Path)
 	if err != nil {
 		return err

server/server_test.go

@@ -533,6 +533,17 @@ func (cli *testServerClient) runTestLoadData(c *C, server *Server) {
 	}, "LoadData", func(dbt *DBTest) {
 		dbt.mustExec("set @@tidb_dml_batch_size = 3")
 		dbt.mustExec("create table test (a varchar(255), b varchar(255) default 'default value', c int not null auto_increment, primary key(c))")
+		dbt.mustExec("create view v1 as select 1")
+		dbt.mustExec("create sequence s1")
+
+		// can't insert into views (in TiDB) or sequences. issue #20880
+		_, err = dbt.db.Exec("load data local infile '/tmp/load_data_test.csv' into table v1")
+		dbt.Assert(err, NotNil)
+		dbt.Assert(err.Error(), Equals, "Error 1105: can only load data into base tables")
+		_, err = dbt.db.Exec("load data local infile '/tmp/load_data_test.csv' into table s1")
+		dbt.Assert(err, NotNil)
+		dbt.Assert(err.Error(), Equals, "Error 1105: can only load data into base tables")
+
 		rs, err1 := dbt.db.Exec("load data local infile '/tmp/load_data_test.csv' into table test")
 		dbt.Assert(err1, IsNil)
 		lastID, err1 := rs.LastInsertId()