MysqL binlog记录的所有操作实际上都有对应的事件类型的,譬如STATEMENT格式中的DML操作对应的是QUERY_EVENT类型,ROW格式下的DML操作对应的是ROWS_EVENT类型。
首先,看看源码中定义的事件类型
源码位置:MysqL-5.7.14/libbinlogevents/include/binlog_event.h
enum Log_event_type { /** Every time you update this enum (when you add a type),you have to fix Format_description_event::Format_description_event(). */ UNKNowN_EVENT= 0,START_EVENT_V3= 1234tvar_EVENT= 567891011* NEW_LOAD_EVENT is like LOAD_EVENT except that it has a longer sql_ex,allowing multibyte TERMINATED BY etc; both types share the same class (Load_event) NEW_LOAD_EVENT= 1213141516171819* The PRE_GA event numbers were used for 5.1.0 to 5.1.15 and are therefore obsolete. PRE_GA_WRITE_ROWS_EVENT = 202122* The V1 event numbers are used from 5.1.16 until MysqL-trunk-xx WRITE_ROWS_EVENT_V1 = 232425* Something out of the ordinary happened on the master INCIDENT_EVENT= 26* Heartbeat event to be send by master at its idle time to ensure master's online status to slave HEARTBEAT_LOG_EVENT= 27* In some situations,it is necessary to send over ignorable data to the slave: data that a slave can handle in case there is code for handling it,but which can be ignored if it is not recognized. IGnorABLE_LOG_EVENT= 2829* Version 2 of the Row events WRITE_ROWS_EVENT = 3031323334IoUS_GTIDS_LOG_EVENT= 353637 Prepared XA transaction terminal event similar to Xid XA_PREPARE_LOG_EVENT= 38* Add new events here - right above this comment! Existing events (except ENUM_END_EVENT) should never change their numbers ENUM_END_EVENT end marker };
实际上还是蛮多的,下面就挑几个重点的说一下
QUERY_EVENT
QUERY_EVENT以文本的形式来记录事务的操作。
QUERY_EVENT类型的事件通常在以下几种情况下使用:
1. 事务开始时,执行的BEGIN操作。
2. STATEMENT格式中的DML操作
3. ROW格式中的DDL操作
譬如:
MysqL> show binlog events in 'MysqL-bin.000021'; +------------------+-----+-------------+-----------+-------------+-----------------------------------------------+ | Log_name | Pos | Event_type | Server_id | End_log_pos | Info | | MysqL-bin.000021 | 4 | Format_desc | 1 120 | Server ver: 5.6.31-log,binlog ver: 4 | | Query 195 | BEGIN 298 insert into test.t1 values(1,a') | Xid 329 COMMIT xid=25 */ 408 515 use `test`; 2,1)">b') 546 xid=33 ----------------+-----+-------------+-----------+-------------+-----------------------------------------------+
FORMAT_DESCRIPTION_EVENT
FORMAT_DESCRIPTION_EVENT是binlog version 4中为了取代之前版本中的START_EVENT_V3事件而引入的。它是binlog文件中的第一个事件,而且,该事件只会在binlog中出现一次。MysqL根据FORMAT_DESCRIPTION_EVENT的定义来解析其它事件。
它通常指定了MysqL Server的版本,binlog的版本,该binlog文件的创建时间。
譬如:
# at #160817 11:00:10 server id 1 end_log_pos 120 CRC32 0x03010da1 Start: binlog v 4,server v 5.6.31-log created # Warning: this binlog is either in use or was not closed properly.
MysqL| ...
ROWS_EVENT
对于ROW格式的binlog,所有的DML语句都是记录在ROWS_EVENT中。
ROWS_EVENT分为三种:WRITE_ROWS_EVENT,UPDATE_ROWS_EVENT,DELETE_ROWS_EVENT,分别对应insert,update和delete操作。
对于insert操作,WRITE_ROWS_EVENT包含了要插入的数据
对于update操作,UPDATE_ROWS_EVENT不仅包含了修改后的数据,还包含了修改前的值。
对于delete操作,仅仅需要指定删除的主键(在没有主键的情况下,会给定所有列)
对于QUERY_EVENT事件,是以文本形式记录DML操作的。而对于ROWS_EVENT事件,并不是文本形式,所以在通过MysqLbinlog查看基于ROW格式的binlog时,需要指定-vv --base64-output=decode-rows。
譬如:
MysqLMysqL-bin.000027----------------+-----+-------------+-----------+-------------+---------------------------------------+ | Info 000027 188 BEGIN | Table_map 236 | table_id: 80 (test.t1) | Write_rows 278 80 flags: STMT_END_F 309 xid=198 */ 377 425 | Update_rows 475 506 xid=199 574 622 | Delete_rows 664 695 xid=200 13 rows in set (0.00 sec)
XID_EVENT
在事务提交时,不管是STATEMENT还是ROW格式的binlog,都会在末尾添加一个XID_EVENT事件代表事务的结束。该事件记录了该事务的ID,在MysqL进行崩溃恢复时,根据事务在binlog中的提交情况来决定是否提交存储引擎中状态为prepared的事务。
ROTATE_EVENT
当binlog文件的大小达到max_binlog_size的值或者执行flush logs命令时,binlog会发生切换,这个时候会在当前的binlog日志添加一个ROTATE_EVENT事件,用于指定下一个日志的名称和位置。
# at 12012:34:26 server 167 CRC32 0xd965567c Rotate to MysqL-bin.000029 pos: 4
GTID_LOG_EVENT
在启用GTID模式后,MysqL实际上为每个事务都分配了个GTID
譬如:
# at 448160818 5:37:32 server 496 CRC32 0xaeb24aac GTID [commit=yes] SET @@SESSION.GTID_NEXT= 'cad449f2-5d4f-11e6-b353-000c29c64704:3!;
# at 496571 CRC32 0x042ca092 Query thread_id=2 exec_time=0 error_code= SET TIMESTAMP=1471469852; BEGIN 571674 CRC32 0xa35beb37 Query thread_id=; insert into test.t1 values(2,b) 674705 CRC32 0x1905d8c6 Xid = COMMIT*/;
MysqLMysqL-bin.000033----------------+-----+----------------+-----------+-------------+-------------------------------------------------------------------+ | Event_type | Info 000033 | Format_desc 4 | PrevIoUs_gtids 191 | cad449f2-5d4f-11e6-b353-000c29c64704:1 | Gtid 239 SET @@SESSION.GTID_NEXT= cad449f2-5d4f-11e6-b353-000c29c64704:2' | Query 314 BEGIN 417 ') | Xid 448 xid=11 */ 496 cad449f2-5d4f-11e6-b353-000c29c64704:3571 674 705 xid=12 | Rotate 752 000034;pos4 11 rows PREVIoUS_GTIDS_LOG_EVENT开启GTID模式后,每个binlog开头都会有一个PREVIoUS_GTIDS_LOG_EVENT事件,它的值是上一个binlog的PREVIoUS_GTIDS_LOG_EVENT+GTID_LOG_EVENT,实际上,在数据库重启的时候,需要重新填充gtid_executed的值,该值即是最新一个binlog的PREVIoUS_GTIDS_LOG_EVENT+GTID_LOG_EVENT。
譬如:
MysqL0.00 sec) MysqLMysqL-bin.000034----------------+-----+----------------+-----------+-------------+------------------------------------------+ | Info 000034 4 1-3 0.00 sec)MysqL-bin.000033日志中的PrevIoUs_gtids是cad449f2-5d4f-11e6-b353-000c29c64704:1,GTID是cad449f2-5d4f-11e6-b353-000c29c64704:2和cad449f2-5d4f-11e6-b353-000c29c64704:3,这样,在下一个日志,即MysqL-bin.000034中的PrevIoUs_gtids是cad449f2-5d4f-11e6-b353-000c29c64704:1-3。
# at 39:38 server 191 CRC32 0x4e84f3b5 PrevIoUs-GTIDs # cad449f2-5d4f-11e6-b353-000c29c64704:1-3
STOP_EVENT
当MysqL数据库停止时,会在当前的binlog末尾添加一个STOP_EVENT事件表示数据库停止。
譬如:
# at 18:04 server 143 CRC32 0xf20ddc85 Stop
参考
1. MariaDB原理与实现
2. MysqL官方文档