MySQL5.6.37版本，某人在测试环境主库误操作执行删表操作，导致主从断开，在从库查看主从信息如下：

Last_Errno: 1837

Last_Error: Worker 3 failed executing transaction '' at master log mysql-bin.013343, end_log_pos 289330740; Error 'When @@SESSION.GTID_NEXT is set to a GTID,

you must explicitly set it to a different value after a COMMIT or ROLLBACK. Please check GTID_NEXT variable manual page for detailed explanation. Current

@@SESSION.GTID_NEXT is '07fd3067-b250-11e7-a2f0-1866da9e4b15:2618462902'.' on query. Default database: 'DBNAME'. Query: 'DROP TABLE IF EXISTS TABLENAME_1,TABLENAME_2 ...

执行删表操作怎么可能会导致主从断开，问后知道是通过某工具误操作导致了删表，并立刻停止了。

故障可能原因：

1、create table table_name as select * from table_name; 会拆分成 creat table 和 insert 两个事务，传到slave时，slave执行完 create table以后，没有insert的GTID，于是报错

2、MyISAM 存储引擎，myisam引擎支持insert delayed语法，insert delay是异步写入，也就是一旦执行立即返回给客户端成功。mysql内部处理insert delay时，会将多个线程的insert合并后一起执行，但是只生成了一个GTID；于是传到slave后，由于是myisam表，从库的同样只能执行第一条SQL，于是报错

3、主库innodb执行一个事务，只产生一个gtid，myisam不支持事务，事务的第一条执行完以后，第二个sql就没有gtid，于是报错

4、临时表

5、BUG

本次故障

1、检查对应的库没有MyISAM表：

select table_schema,table_name,engine from information_schema.tables where engine !='innodb' and table_schema = 'DBNAME';

2、检查过enforce_gtid_consistency主从库都为on，CREATE TABLE ... SELECT语句不能执行成功，并且这次故障并不涉及CREATE TABLE ... SELECT语句，故排除

3、主从存储引擎一致

4、没有临时表

在主库审计日志查看，执行了drop schema dbname;

20200707 12:55:20 '/* ApplicationName=DataGrip 2020.1.4 */ drop schema DBNAME'

查看主库 binlog ：

# at 289328506

#200707 12:55:08 server id 100 end_log_pos 289328554 CRC32 0x1401e82a GTID [commit=yes]

SET @@SESSION.GTID_NEXT= '07fd3067-b250-11e7-a2f0-1866da9e4b15:2618462902'/*!*/;

# at 289328554

#200707 12:55:08 server id 100 end_log_pos 289329642 CRC32 0x0728afdf Querythread_id=2388454119exec_time=12error_code=0

SET TIMESTAMP=1594097708/*!*/;

SET @@session.sql_mode=270532608/*!*/;

/*!\C utf8mb4 *//*!*/;

SET @@session.character_set_client=45,@@session.collation_connection=45,@@session.collation_server=33/*!*/;

DROP TABLE IF EXISTS TABLENAME_1,TABLENAME_2,TABLENAME_3,TABLENAME_4,....../*!*/;

# at 289329642

#200707 12:55:08 server id 100 end_log_pos 289330740 CRC32 0x0d0122e4 Querythread_id=2388454119exec_time=12error_code=0

SET TIMESTAMP=1594097708/*!*/;

DROP TABLE IF EXISTS TABLENAME_5,TABLENAME_6,TABLENAME_7,TABLENAME_8,....../*!*/;

# at 289330740

#200707 12:55:08 server id 100 end_log_pos 289331832 CRC32 0xd8409afa Querythread_id=2388454119exec_time=12error_code=0

SET TIMESTAMP=1594097708/*!*/;

DROP TABLE IF EXISTS TABLENAME_9,TABLENAME_10,TABLENAME_11,TABLENAME_12,....../*!*/;

# at 289331832

#200707 12:55:08 server id 100 end_log_pos 289332298 CRC32 0xa6657cc5 Querythread_id=2388454119exec_time=12error_code=0

SET TIMESTAMP=1594097708/*!*/;

DROP TABLE IF EXISTS TABLENAME_13,TABLENAME_14,TABLENAME_15,TABLENAME_16,....../*!*/;

# at 289332298

#200707 12:55:20 server id 100 end_log_pos 289332346 CRC32 0x0cc19e83 GTID [commit=yes]

SET @@SESSION.GTID_NEXT= '07fd3067-b250-11e7-a2f0-1866da9e4b15:2618462903'/*!*/;

查看从库 binlog ：

# at 19856236

#200707 12:55:08 server id 100 end_log_pos 19856284 CRC32 0x5e42595eGTID [commit=yes]

SET @@SESSION.GTID_NEXT= '07fd3067-b250-11e7-a2f0-1866da9e4b15:2618462902'/*!*/;

DROP TABLE IF EXISTS TABLENAME_1,TABLENAME_2,TABLENAME_3,TABLENAME_4,......# at 19857398

#200707 12:55:23 server id 100 end_log_pos 19857446 CRC32 0x81998bd5GTID [commit=yes]

SET @@SESSION.GTID_NEXT= '07fd3067-b250-11e7-a2f0-1866da9e4b15:2618463065'/*!*/;

# at 19857446

#200707 12:55:23 server id 100 end_log_pos 19857509 CRC32 0x0916a5e2Querythread_id=2388456043exec_time=0 error_code=0

SET TIMESTAMP=1594097723/*!*/;

SET @@session.sql_mode=524288/*!*/;

/*!\C utf8 *//*!*/;

SET @@session.character_set_client=33,@@session.collation_connection=33,@@session.collation_server=33/*!*/;

BEGIN

/*!*/;

# at 19857509

#200707 12:55:23 server id 100 end_log_pos 19859435 CRC32 0x2eec3842Rows_query

# insert into talename....

......

......

#200707 12:55:23 server id 100 end_log_pos 19860287 CRC32 0xc983ec89Xid = 5405680966

COMMIT/*!*/;

# at 19860287

#200707 12:55:08 server id 100 end_log_pos 19861411 CRC32 0x20f2bc78Querythread_id=2388454119exec_time=1669 error_code=0

SET TIMESTAMP=1594097708/*!*/;

SET @@session.sql_mode=270532608/*!*/;

/*!\C utf8mb4 *//*!*/;

SET @@session.character_set_client=45,@@session.collation_connection=45,@@session.collation_server=33/*!*/;

DROP TABLE IF EXISTS TABLENAME_5,TABLENAME_6,TABLENAME_7,TABLENAME_8,....../*!*/;

# at 19861411

#200707 12:55:08 server id 100 end_log_pos 19862529 CRC32 0x35204dfeQuerythread_id=2388454119exec_time=1672 error_code=0

SET TIMESTAMP=1594097708/*!*/;

DROP TABLE IF EXISTS TABLENAME_9,TABLENAME_10,TABLENAME_11,TABLENAME_12,....../*!*/;

# at 19862529

#200707 12:55:23 server id 100 end_log_pos 19862577 CRC32 0x48b02b33GTID [commit=yes]

SET @@SESSION.GTID_NEXT= '07fd3067-b250-11e7-a2f0-1866da9e4b15:2618463066'/*!*/;

1、因为数据库开启了GTID复制，每一个GTID需要与一个唯一的事务对应，"drop schema dbname;" 在从库将删表语句拆分成了多个语句。

2、查看主从GTID，发现从库GTID缺少了从'07fd3067-b250-11e7-a2f0-1866da9e4b15:2618462903' 至 '07fd3067-b250-11e7-a2f0-1866da9e4b15:2618463064'信息

3、而且从库在GTID为'07fd3067-b250-11e7-a2f0-1866da9e4b15:2618462902'时执行了一个DROP TABLE IF EXISTS语句后，直接进入GTID为'07fd3067-b250-11e7-a2f0-1866da9e4b15:2618463065' 执行insert into语句并COMMIT

4、COMMIT后，正常需要设置不同的@@SESSION.GTID_NEXT，但是没有，而是再次执行DROP TABLE IF EXISTS语句。事务在GTID为'07fd3067-b250-11e7-a2f0-1866da9e4b15:2618462902'后发生了异常拆分，所以主从复制发生报错。