最近查看慢查询日志，一直有看到SELECT * FROM tb_name的SQL语句，在之前SQL审核的时候，也没发现有这些SQL的存在，所以很好奇这里怎么出现的，后来用了vc-mysql-sniffer脚本去抓SQL来分析，也没有找出SELECT * 之类的SQL，下面我上图让分析一下：
slow.log
可以看到大量的SELECT * 的SQL，如果细心的小伙伴会发现，SQL之前都有use某个库，从这里应该可以想到一般程序里不可能会出现use xxx之类的SQL，所以可以排除程序在作怪的可能了，一般use某个库再执行SQL，普遍都是人为操作的比较多，但是DB服务器只有我才有权限，所以觉得好奇怪，在想这些SQL从哪里飞出来的，后来认真分析了一下slow log发现每次出现这类SQL的频率都是间隔一个小时左右，后来我再检查一下些库是否有定时器，结果发现没有，这下我就大概知道什么原因了，我在slave上是每个小时一备份的，以下是模拟的过程：
在测试服务器把慢查询时间设置为0.5s，然后把查询日志打开：（测试完后，记得关掉general_log）
mysql> set global long_query_time=0.5; Query OK, 0 rows affected (0.00 sec) mysql> set global general_log=on; Query OK, 0 rows affected (0.01 sec)
然后把备份导入测试服务器：
[root@Test_server ~]# mysql -uroot -p123456 testdb < ./testdb.sql
[root@Test_server ~]#
在session1窗口执行查看general_log的操作：
[root@Test_server ~]# tail -f /data/mysql3306/Test_server.log
在session2窗口执行备份操作：
[root@Test_server ~]# mysqldump -uroot -p123456 -R --events --triggers=true --master-data=2 --single-transaction testdb > testdb.sql
再在session1上查看打印日志：
[root@Test_server ~]# tail -f /data/mysql3306/Test_server.log /data/service/mysql/bin/mysqld, Version: 5.6.25-log (MySQL Community Server (GPL)). started with: Tcp port: 3306 Unix socket: /tmp/mysql3306.sock Time Id Command Argument 151006 14:21:21 583376 Quit 151006 14:21:22 583389 Connect root@localhost on 583389 Query select @@version_comment limit 1 151006 14:21:24 583389 Query show variables like '%gen%' 151006 14:21:25 583389 Quit 151006 14:43:18 583786 Connect root@localhost on 583786 Query /*!40100 SET @@SQL_MODE='' */ 583786 Query /*!40103 SET TIME_ZONE='+00:00' */ 583786 Query FLUSH /*!40101 LOCAL */ TABLES 151006 14:43:19 583786 Query FLUSH TABLES WITH READ LOCK 583786 Query SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ 583786 Query START TRANSACTION /*!40100 WITH CONSISTENT SNAPSHOT */ 583786 Query SHOW VARIABLES LIKE 'gtid\_mode' 583786 Query SHOW MASTER STATUS 583786 Query UNLOCK TABLES 583786 Query SELECT LOGFILE_GROUP_NAME, FILE_NAME, TOTAL_EXTENTS, INITIAL_SIZE, ENGINE, EXTRA FROM INFORMATION_SCHEMA.FILES WHERE FILE_TYPE = 'UNDO LOG' AND FILE_NAME IS NOT NULL AND LOGFILE_GROUP_NAME IN (SELECT DISTINCT LOGFILE_GROUP_NAME FROM INFORMATION_SCHEMA.FILES WHERE FILE_TYPE = 'DATAFILE' AND TABLESPACE_NAME IN (SELECT DISTINCT TABLESPACE_NAME FROM INFORMATION_SCHEMA.PARTITIONS WHERE TABLE_SCHEMA IN ('testdb'))) GROUP BY LOGFILE_GROUP_NAME, FILE_NAME, ENGINE ORDER BY LOGFILE_GROUP_NAME 583786 Query SELECT DISTINCT TABLESPACE_NAME, FILE_NAME, LOGFILE_GROUP_NAME, EXTENT_SIZE, INITIAL_SIZE, ENGINE FROM INFORMATION_SCHEMA.FILES WHERE FILE_TYPE = 'DATAFILE' AND TABLESPACE_NAME IN (SELECT DISTINCT TABLESPACE_NAME FROM INFORMATION_SCHEMA.PARTITIONS WHERE TABLE_SCHEMA IN ('testdb')) ORDER BY TABLESPACE_NAME, LOGFILE_GROUP_NAME 151006 14:43:20 583786 Query SHOW VARIABLES LIKE 'ndbinfo\_version' 583786 Init DB testdb 583786 Query SAVEPOINT sp 583786 Query show tables 583786 Query show table status like 'sys\_config' 583786 Query SET SQL_QUOTE_SHOW_CREATE=1 583786 Query SET SESSION character_set_results = 'binary' 583786 Query show create table `sys_config` 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query show fields from `sys_config` 583786 Query SELECT /*!40001 SQL_NO_CACHE */ * FROM `sys_aa` 583786 Query SET SESSION character_set_results = 'binary' 583786 Query use `testdb` 583786 Query select @@collation_database 583786 Query SHOW TRIGGERS LIKE 'sys\_config' 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query ROLLBACK TO SAVEPOINT sp 583786 Query show table status like 'testdb\_auto\_login' 583786 Query SET SQL_QUOTE_SHOW_CREATE=1 583786 Query SET SESSION character_set_results = 'binary' 583786 Query show create table `testdb_auto_login` 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query show fields from `testdb_auto_login` 583786 Query SELECT /*!40001 SQL_NO_CACHE */ * FROM `testdb_bb` 583786 Query SET SESSION character_set_results = 'binary' 583786 Query use `testdb` 583786 Query select @@collation_database 583786 Query SHOW TRIGGERS LIKE 'testdb\_auto\_login' 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query ROLLBACK TO SAVEPOINT sp 583786 Query show table status like 'testdb\_fans' 583786 Query SET SQL_QUOTE_SHOW_CREATE=1 583786 Query SET SESSION character_set_results = 'binary' 583786 Query show create table `testdb_fans` 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query show fields from `testdb_fans` 583786 Query SELECT /*!40001 SQL_NO_CACHE */ * FROM `testdb_cc` 583786 Query SET SESSION character_set_results = 'binary' 583786 Query use `testdb` 583786 Query select @@collation_database 583786 Query SHOW TRIGGERS LIKE 'testdb\_fans' 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query ROLLBACK TO SAVEPOINT sp 583786 Query show table status like 'testdb\_media' 583786 Query SET SQL_QUOTE_SHOW_CREATE=1 583786 Query SET SESSION character_set_results = 'binary' 583786 Query show create table `testdb_media` 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query show fields from `testdb_media` 583786 Query SELECT /*!40001 SQL_NO_CACHE */ * FROM `testdb_dd` 583786 Query SET SESSION character_set_results = 'binary' 583786 Query use `testdb` 583786 Query select @@collation_database 583786 Query SHOW TRIGGERS LIKE 'testdb\_media' 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query ROLLBACK TO SAVEPOINT sp 583786 Query show table status like 'testdb\_message' 583786 Query SET SQL_QUOTE_SHOW_CREATE=1 583786 Query SET SESSION character_set_results = 'binary' 583786 Query show create table `testdb_message` 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query show fields from `testdb_message` 583786 Query SELECT /*!40001 SQL_NO_CACHE */ * FROM `testdb_ee` 151006 14:43:23 583786 Query SET SESSION character_set_results = 'binary' 583786 Query use `testdb` 583786 Query select @@collation_database 583786 Query SHOW TRIGGERS LIKE 'testdb\_message' 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query ROLLBACK TO SAVEPOINT sp 583786 Query show table status like 'testdb\_qrcode' 583786 Query SET SQL_QUOTE_SHOW_CREATE=1 583786 Query SET SESSION character_set_results = 'binary' 583786 Query show create table `testdb_qrcode` 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query show fields from `testdb_qrcode` 583786 Query SELECT /*!40001 SQL_NO_CACHE */ * FROM `testdb_ff` 583786 Query SET SESSION character_set_results = 'binary' 583786 Query use `testdb` 583786 Query select @@collation_database 583786 Query SHOW TRIGGERS LIKE 'testdb\_qrcode' 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query ROLLBACK TO SAVEPOINT sp 583786 Query show table status like 'testdb\_ticket' 583786 Query SET SQL_QUOTE_SHOW_CREATE=1 583786 Query SET SESSION character_set_results = 'binary' 583786 Query show create table `testdb_ticket` 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query show fields from `testdb_ticket` 583786 Query SELECT /*!40001 SQL_NO_CACHE */ * FROM `testdb_gg` 583786 Query SET SESSION character_set_results = 'binary' 583786 Query use `testdb` 583786 Query select @@collation_database 583786 Query SHOW TRIGGERS LIKE 'testdb\_ticket' 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query ROLLBACK TO SAVEPOINT sp 583786 Query show table status like 'testdb\_token' 583786 Query SET SQL_QUOTE_SHOW_CREATE=1 583786 Query SET SESSION character_set_results = 'binary' 583786 Query show create table `testdb_token` 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query show fields from `testdb_token` 583786 Query SELECT /*!40001 SQL_NO_CACHE */ * FROM `testdb_hh` 583786 Query SET SESSION character_set_results = 'binary' 583786 Query use `testdb` 583786 Query select @@collation_database 583786 Query SHOW TRIGGERS LIKE 'testdb\_token' 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query ROLLBACK TO SAVEPOINT sp 583786 Query show table status like 'wexin\_template\_msg' 583786 Query SET SQL_QUOTE_SHOW_CREATE=1 583786 Query SET SESSION character_set_results = 'binary' 583786 Query show create table `wexin_template_msg` 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query show fields from `wexin_template_msg` 583786 Query SELECT /*!40001 SQL_NO_CACHE */ * FROM `wexin_tem` 583786 Query SET SESSION character_set_results = 'binary' 583786 Query use `testdb` 583786 Query select @@collation_database 583786 Query SHOW TRIGGERS LIKE 'wexin\_template\_msg' 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query ROLLBACK TO SAVEPOINT sp 583786 Query show table status like 'wexin\_template\_msg\_data' 583786 Query SET SQL_QUOTE_SHOW_CREATE=1 583786 Query SET SESSION character_set_results = 'binary' 583786 Query show create table `wexin_template_msg_data` 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query show fields from `wexin_template_msg_data` 583786 Query SELECT /*!40001 SQL_NO_CACHE */ * FROM `testdb_template` 583786 Query SET SESSION character_set_results = 'binary' 583786 Query use `testdb` 583786 Query select @@collation_database 583786 Query SHOW TRIGGERS LIKE 'wexin\_template\_msg\_data' 583786 Query SET SESSION character_set_results = 'utf8' 583786 Query ROLLBACK TO SAVEPOINT sp 583786 Query RELEASE SAVEPOINT sp 583786 Query show events 583786 Query use `testdb` 583786 Query select @@collation_database 583786 Query SET SESSION character_set_results = 'binary' 583786 Query SHOW FUNCTION STATUS WHERE Db = 'testdb' 583786 Query SHOW PROCEDURE STATUS WHERE Db = 'testdb' 583786 Query SET SESSION character_set_results = 'utf8' 151006 14:43:27 583786 Quit