text: --- Case Type： Comment
  --- Case Name： 对类型转换添加注释
  
  
  --给类型转换添加注释信息
  comment on cast(circle as point) is '测试类型转换注释添加成功';
  
  --在相关系统表中查看注释是否添加成功
  select description from pg_description where objoid=(select oid from pg_cast where castsource=(select oid from pg_type where typname='circle') and casttarget=(select oid from pg_type where typname='point'));
  
  
  
  
  