收到客戶一個有意思的需求

• A例項下的demo庫的t1要用複製同步到B例項,為了防止B例項會對這些資料做修改操作,需要限制B例項對t1表的修改操作.只允許查

第一想到的是用許可權管理控制,收回B例項下所有使用者對t1表的許可權,但這個操作在5.7裡面十分繁瑣,且5.7不支援回收部分許可權(8.0支援)

搜尋網路上的一些解決方案,發現用觸發器的方式十分合適,分別建立3個觸發器,來控制對t1表的insert,update,delete行為,這樣就做到了,A例項用複製同步時不受到影響但B例項想修改這些資料不允許操作

/* triggers */
delimiter //

DROP TRIGGER IF EXISTS stop_table_insert;
CREATE TRIGGER stop_table_insert
  BEFORE INSERT ON `demo`.`t1`
FOR EACH ROW
BEGIN
   SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'This table Only replication synchronization is allowed, but data cannot be modified';
END;//

DROP TRIGGER IF EXISTS stop_table_update;
CREATE TRIGGER stop_table_update
  BEFORE UPDATE ON `demo`.`t1`
FOR EACH ROW
BEGIN 
   SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'This table Only replication synchronization is allowed, but data cannot be modified';
END;//

DROP TRIGGER IF EXISTS stop_table_delete;
CREATE TRIGGER stop_table_delete
  BEFORE DELETE ON `demo`.`t1`
FOR EACH ROW
BEGIN
   SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'This table Only replication synchronization is allowed, but data cannot be modified';
END;//

delimiter ;
 

注意: SQLSTATE '45000'是使用者自定義錯誤狀態值的標準寫法,官方文件描述是: To signal a generic SQLSTATE value, use '45000', which means “unhandled user-defined exception" ,MESSAGE_TEXT可隨意定義

參考連結

• https://stackoverflow.com/questions/12349640/read-only-table-in-mysql