PURGE PurposeUse the PURGE statement to remove a table or index from your recycle bin and release all of the space associated with the object, or to remove the entire recycle bin, or to remove part of all of a dropped tablespace from the recycle bin.
1.只批量插入: insert into WXPAY_ACCOUNT(id ,out_trade_no ,transaction_id)select SEQ_WXPAY_ACCOUNT.nextval id,a.* FROM ( SELECT#{wxpayAccount.outTradeNo ,jdbcType=VARCHAR},#{wxpayAccount.transactionId ,jdbcType=VARCHAR}FROM dual ) a 2.批量插入(存在不插入) merge int
要明白什么清空(purge)操作,你得明白什么是事务的多版本控制,即MVCC(multi-version concurrency control).Innodb为了实现MVCC, 需要在表空间内保存老版本的记录信息,这些信息存储于回滚段中(rollback segment),所谓回滚段,在物理存储上是UNDO log的记录. Purge到底做了些什么?其实它就相当于一个垃圾收集器.取个例子,当用户下一个命令,如 “DELETE FROM t WHERE c = 1;”, InnoDB 不会马上删
1.版本 1)操作系统 cat /etc/issueCentOS release 6.6 (Final)Kernel \r on an \m cat /proc/versionLinux version 2.6.32-504.el6.x86_64 (mockbuild@c6b9.bsys.dev.centos.org) (gcc version 4.4.7 20120313 (Red Hat 4.4.7-11) (GCC) ) #1 SMP Wed Oct 15 04:27:16 UTC 201