GaussDB(DWS)里可直接执行的MySQL语法的DDL

针对MySQL->GaussDB(DWS)的实时同步，DRS不再对增量的DDL做转换，MySQL的DDL将原样在GaussDB(DWS)里执行。目前GaussDB(DWS)里能直接执行的DDL有：

alter table test add column c1 varchar(20);  
alter table test  drop column c1;  
drop table test;  
create table test(id int primary key ,name varchar(20)); 
create index test on db1.test (name); 
truncate table db1.test;

无法直接执行的DDL有：

alter table db1.test rename to db1.test_bak;
rename table test to test_bak;
alter table db1.test modify column c1 varchar(40);
alter table db1.test change column c1 c1 varchar(50);
alter table db1.test add index/key index_1(name);
alter table db1.test drop index/key index_1;