MySQL innodb事務(wù)的實(shí)現(xiàn)方式

這篇文章主要講解了“MySQL innodb事務(wù)的實(shí)現(xiàn)方式”，文中的講解內(nèi)容簡(jiǎn)單清晰，易于學(xué)習(xí)與理解，下面請(qǐng)大家跟著小編的思路慢慢深入，一起來(lái)研究和學(xué)習(xí)“MySQL innodb事務(wù)的實(shí)現(xiàn)方式”吧！

 【1】Redo Log
 在Innodb存儲(chǔ)引擎中，事務(wù)日志是通過(guò)redo和innodb的存儲(chǔ)引擎日志緩沖（Innodb log buffer）來(lái)實(shí)現(xiàn)的，當(dāng)開(kāi)始一個(gè)事務(wù)的時(shí)候，會(huì)記錄該事務(wù)的lsn(log sequence number)號(hào); 當(dāng)事務(wù)執(zhí)行時(shí)，會(huì)往InnoDB存儲(chǔ)引擎的日志
 的日志緩存里面插入事務(wù)日志；當(dāng)事務(wù)提交時(shí)，必須將存儲(chǔ)引擎的日志緩沖寫(xiě)入磁盤(pán)（通過(guò)innodb_flush_log_at_trx_commit來(lái)控制），也就是寫(xiě)數(shù)據(jù)前，需要先寫(xiě)日志。這種方式稱為“預(yù)寫(xiě)日志方式”，
 innodb通過(guò)此方式來(lái)保證事務(wù)的完整性。也就意味著磁盤(pán)上存儲(chǔ)的數(shù)據(jù)頁(yè)和內(nèi)存緩沖池上面的頁(yè)是不同步的，是先寫(xiě)入redo log，然后寫(xiě)入data file，因此是一種異步的方式。通過(guò) show engine innodb status\G 來(lái)觀察之間的差距

 -- 建立一張表z，然后建立一個(gè)往表導(dǎo)入數(shù)據(jù)的存儲(chǔ)過(guò)程load_test。通過(guò)命令show engine innodb status觀察當(dāng)前的redo日志情況

create table z(a int, primary key(a))engine=innodb;

DELIMITER $$
DROP PROCEDURE IF EXISTS `test`.`load_test`$$
CREATE PROCEDURE load_test(COUNT INT)
BEGIN
  DECLARE i INT UNSIGNED DEFAULT 0;
  START TRANSACTION;
  WHILE i < COUNT DO
	REPLACE INTO z SELECT i;  -- 用replace是因?yàn)樾枰貜?fù)調(diào)用，避免主鍵重復(fù)insert報(bào)錯(cuò)。
   	SET i=i+1;
	END WHILE;
 COMMIT;
END;
$$

......
---
LOG
---
Log sequence number 20499052099  當(dāng)前的LSN
Log flushed up to   20499052099  表示刷新到redo log的LSN
Pages flushed up to 20499052099  表示刷新到磁盤(pán)的lsn
Last checkpoint at  20499052099  
0 pending log writes, 0 pending chkp writes
373 log i/o's done, 0.00 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total memory allocated 137363456; in additional pool allocated 0
Dictionary memory allocated 1270857
Buffer pool size   8191
Free buffers       7562
Database pages     612
Old database pages 205
Modified db pages  0
Pending reads 0
......

mysql> call test.load_test(100000);
Query OK, 0 rows affected, 1 warning (6.28 sec)

mysql> show engine innodb status\G
...... 
---
LOG
---
Log sequence number 20504734913
Log flushed up to   20504734913
Pages flushed up to 20504734913
Last checkpoint at  20504734913
0 pending log writes, 0 pending chkp writes
398 log i/o's done, 0.38 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
...... 
看來(lái)Log sequence number和Log flushed up以及Pages flushed u3個(gè)還是一樣的。

再多導(dǎo)入點(diǎn)數(shù)據(jù)，重新開(kāi)啟另外一個(gè)窗口看看innodb狀態(tài)
mysql> call test.load_test(1000000);
mysql> show engine innodb status\G
......
---
LOG
---
Log sequence number 20527044411
Log flushed up to   20525763843
Pages flushed up to 20517902997
Last checkpoint at  20504829471
0 pending log writes, 0 pending chkp writes
432 log i/o's done, 1.26 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------

這次看到的show engine innodb status的結(jié)果就不一樣了，Log sequence number > Log flushed up > Pages flushed up > Last checkpoint，所以從這里也可以看出，先寫(xiě)redo日志，再寫(xiě)數(shù)據(jù)文件
在實(shí)際寫(xiě)比較頻繁的productiion上面，這3個(gè)值都會(huì)是不一樣的。

【2】Undo 
undo的記錄正好與redo的相反，insert變成delete，update變成相反的update，redo放在redo file里面。而undo放在一個(gè)內(nèi)部的一個(gè)特殊segment上面，存儲(chǔ)與共享表空間內(nèi)（ibdata1或者ibdata2中）。
py_innodb_page_info.py
下載地址： wget http://david-mysql-tools.googlecode.com/svn-history/r15/trunk/py_innodb_page_type/py_innodb_page_info.py
[root@mysql data56]# python /root/py_innodb_page_info.py /data56/ibdata1 
Traceback (most recent call last):
  File "/root/py_innodb_page_info.py", line 3, in <module>
    import mylib
ImportError: No module named mylib
[root@mysql data56]# 
還需要下載 mylib.py和include.py文件，并和py_innodb_page_info.py放在一個(gè)目錄之下

wget http://david-mysql-tools.googlecode.com/svn-history/r15/trunk/py_innodb_page_type/mylib.py
wget http://david-mysql-tools.googlecode.com/svn-history/r15/trunk/py_innodb_page_type/include.py
ps：有的時(shí)候network會(huì)斷掉，要多執(zhí)行幾次wget去下載。

[root@mysql ~]#  python /root/py_innodb_page_info.py /data56/ibdata1

Total number of page: 8960:
Insert Buffer Free List: 1035
Insert Buffer Bitmap: 1
System Page: 134
Transaction system Page: 1
Freshly Allocated Page: 4010
Undo Log Page: 1556
File Segment inode: 5
B-tree Node: 2217
File Space Header: 1
[root@mysql ~]# 
[root@mysql ~]#

undo不是物理恢復(fù)，是邏輯恢復(fù)，因?yàn)樗峭ㄟ^(guò)執(zhí)行相反的dml語(yǔ)句來(lái)實(shí)現(xiàn)的。而且不會(huì)回收因?yàn)閕nsert和upate而新增加的page頁(yè)的。
undo頁(yè)的回收是通過(guò)master thread線程來(lái)實(shí)現(xiàn)的。

驗(yàn)證row模式下，生產(chǎn)的binlog傳到從庫(kù)上面，大概需要多久！
導(dǎo)出
time /usr/local/mysql56/bin/mysqldump --socket=/data56/mysql.sock -uroot -p123456 -P3307 --extended-insert=false --all-databases> /root/adb.sql
[root@mysql ~]# time /usr/local/mysql56/bin/mysqldump --socket=/data56/mysql.sock -uroot -p123456 -P3307 --extended-insert=false --all-databases> /root/adb.sql
Warning: Using a password on the command line interface can be insecure.

real    5m10.757s
user    2m42.137s
sys     0m11.346s

導(dǎo)入
time /usr/local/mysql56/bin/mysql --socket=/data56/mysql.sock -uroot -p123456 -P3307 < /root/adb.sql
在從庫(kù)上面檢查：
mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 10.88.49.119
                  Master_User: repl
                  Master_Port: 3307
                Connect_Retry: 60
              Master_Log_File: mysql56-bin.000008
          Read_Master_Log_Pos: 513272653
               Relay_Log_File: mysql56-relay-bin.000019
                Relay_Log_Pos: 103964146
        Relay_Master_Log_File: mysql56-bin.000008
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 418536570
              Relay_Log_Space: 513273109
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 857
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 11901
                  Master_UUID: a6a1d870-80b5-11e2-84d2-00155d016a07
             Master_Info_File: /data56/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: System lock
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 
                Auto_Position: 0
1 row in set (0.00 sec)

ps：Seconds_Behind_Master: 857，有延時(shí)的情況出現(xiàn)，可見(jiàn)在row模式下，import6G的單調(diào)insert的sql的時(shí)候，有延時(shí)。

感謝各位的閱讀，以上就是“MySQL innodb事務(wù)的實(shí)現(xiàn)方式”的內(nèi)容了，經(jīng)過(guò)本文的學(xué)習(xí)后，相信大家對(duì)MySQL innodb事務(wù)的實(shí)現(xiàn)方式這一問(wèn)題有了更深刻的體會(huì)，具體使用情況還需要大家實(shí)踐驗(yàn)證。這里是億速云，小編將為大家推送更多相關(guān)知識(shí)點(diǎn)的文章，歡迎關(guān)注！