近期在項目上遇到遇到一個頭疼的問題，前方銷售團隊反饋了一個客戶那邊在創建用戶（save object to DB）報錯了以後，前臺展示了錯誤，但是數據庫卻保存了這條記錄。

接到這個BUG以後，第一時間查看了事物是否正確回滾，排查了代碼後發現事物回滾成功，並且在我的環境下回滾成功，錯誤沒有復現，

這個時候就比較棘手了，客戶的事物回滾失敗，但是我們的回滾成功，我們的項目使用的是grails框架做的，查詢了grails聲明性事物回滾的規則，我們的代碼沒有問題，那我就把問題轉移到了數據庫身上，

要了客戶的數據庫，以SQL的形式把數據庫到出來，和我本地的數據庫表進行比對，在比對的過程中發現了不同之處

客戶的SQL（mysql）

ENGINE=MyISAM AUTO_INCREMENT=522 DEFAULT CHARSET=utf8

ENGINE=InnoDB AUTO_INCREMENT=22 DEFAULT CHARSET=utf8

我們的SQL

發現問題所在，我們用的數據庫引擎是InnoDB，而客戶使用的是MYISAM，查詢這兩種引擎不同之處

https://dev.mysql.com/doc/refman/5.6/en/storage-engines.html

MySQL 5.6 Supported Storage Engines

InnoDB: The 
 
default storage engine in MySQL 5.6. InnoDB is a transaction-safe (ACID compliant) storage engine for MySQL that has commit, rollback, and crash-recovery capabilities to protect user data. InnoDB row-level locking (without escalation to coarser granularity locks) and Oracle-style consistent nonlocking reads increase multi-
 
user concurrency and performance. InnoDB stores user data in clustered indexes to reduce I/O for common queries based on primary keys. To maintain data integrity, InnoDB also supports FOREIGN KEY referential-integrity constraints. For more information about InnoDB, see Chapter 14, The InnoDB Storage Engine.

MyISAM: These tables have a small footprint. Table-level locking limits the performance in read/write workloads, so it is often used in read-only or read-mostly workloads in Web and data warehousing configurations.

Memory: Stores all data in RAM, for fast access in environments that require quick lookups of non-critical data. This engine was formerly known as the HEAP engine. Its use cases are decreasing; InnoDB with its buffer pool memory area provides a general-purpose and durable way to keep most or all data in memory, and NDBCLUSTER provides fast key-value lookups for huge distributed data sets.

CSV: Its tables are really text files with comma-separated values. CSV tables let you import or dump data in CSV format, to exchange data with scripts and applications that read and write that same format. Because CSV tables are not indexed, you typically keep the data in InnoDB tables during normal operation, and only use CSV tables during the import or export stage.

Archive: These compact, unindexed tables are intended for storing and retrieving large amounts of seldom-referenced historical, archived, or security audit information.

Blackhole: The Blackhole storage engine accepts but does not store data, similar to the Unix /dev/null device. Queries always return an empty set. These tables can be used in replication configurations where DML statements are sent to slave servers, but the master server does not keep its own copy of the data.

NDB (also known as NDBCLUSTER)—This clustered database engine is particularly suited for applications that require the highest possible degree of uptime and availability.

InnoDB支持事物，而MyISAM不支持事物，

在次復現錯誤，錯誤復現出來。

解決方式：

修改這張表的engine

alter table user engine=InnoDB

修改後再次測試，事物回滾成功。

bug解決。

為了避免再次創建表的engine是MyISAM引擎，修改mysql默認引擎，在修改之前查看數據庫支持的所有引擎

mysql> show engines;

+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine             | Support | Comment                                                        | Transactions | XA   | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| InnoDB             | DEFAULT | Supports transactions, row-level locking, and foreign keys     | YES          | YES  | YES        |
| MRG_MYISAM         | YES     | Collection of identical MyISAM tables                          | NO           | NO   | NO         |
| MEMORY             | YES     | Hash based, stored in memory, useful for temporary tables      | NO           | NO   | NO         |
| BLACKHOLE          | YES     | /dev/null storage engine (anything you write to it disappears) | NO           | NO   | NO         |
| MyISAM             | YES     | MyISAM storage engine                                          | NO           | NO   | NO         |
| CSV                | YES     | CSV storage engine                                             | NO           | NO   | NO         |
| ARCHIVE            | YES     | Archive storage engine                                         | NO           | NO   | NO         |
| PERFORMANCE_SCHEMA | YES     | Performance Schema                                             | NO           | NO   | NO         |
| FEDERATED          | NO      | Federated MySQL storage engine                                 | NULL         | NULL | NULL       |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+

存在InnoDB

在配置文件my.cnf中的 [mysqld] 下面加入default-storage-engine=INNODB 一句，保存。

重啟mysql服務器：mysqladmin -u root -p shutdown或者service mysqld restart 登錄mysql數據庫，在mysql>提示符下搞入show engines;命令。如果出現 InnoDB |DEFAULT，則表示我們 設置InnoDB為默認引擎成功。

mysql的engine不同，導致事物回滾失敗的問題