MySQL binlog中的事件类型

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= ,
  START_EVENT_V3= ,
  QUERY_EVENT= ,
  STOP_EVENT= ,
  ROTATE_EVENT= ,
  INTVAR_EVENT= ,
  LOAD_EVENT= ,
  SLAVE_EVENT= ,
  CREATE_FILE_EVENT= ,
  APPEND_BLOCK_EVENT= ,
  EXEC_LOAD_EVENT= ,
  DELETE_FILE_EVENT= ,
  /**
    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= ,
  RAND_EVENT= ,
  USER_VAR_EVENT= ,
  FORMAT_DESCRIPTION_EVENT= ,
  XID_EVENT= ,
  BEGIN_LOAD_QUERY_EVENT= ,
  EXECUTE_LOAD_QUERY_EVENT= ,

  TABLE_MAP_EVENT = ,

  /**
    The PRE_GA event numbers were used for 5.1.0 to 5.1.15 and are
    therefore obsolete.
   */
  PRE_GA_WRITE_ROWS_EVENT = ,
  PRE_GA_UPDATE_ROWS_EVENT = ,
  PRE_GA_DELETE_ROWS_EVENT = ,

  /**
    The V1 event numbers are used from 5.1.16 until mysql-trunk-xx
  */
  WRITE_ROWS_EVENT_V1 = ,
  UPDATE_ROWS_EVENT_V1 = ,
  DELETE_ROWS_EVENT_V1 = ,

  /**
    Something out of the ordinary happened on the master
   */
  INCIDENT_EVENT= ,

  /**
    Heartbeat event to be send by master at its idle time
    to ensure master's online status to slave
  */
  HEARTBEAT_LOG_EVENT= ,

  /**
    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= ,
  ROWS_QUERY_LOG_EVENT= ,

  /** Version 2 of the Row events */
  WRITE_ROWS_EVENT = ,
  UPDATE_ROWS_EVENT = ,
  DELETE_ROWS_EVENT = ,

  GTID_LOG_EVENT= ,
  ANONYMOUS_GTID_LOG_EVENT= ,

  PREVIOUS_GTIDS_LOG_EVENT= ,

  TRANSACTION_CONTEXT_EVENT= ,

  VIEW_CHANGE_EVENT= ,

  /* Prepared XA transaction terminal event similar to Xid */
  XA_PREPARE_LOG_EVENT= ,
  /**
    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         |
| mysql-bin.000021 | 120 | Query       |         1 |         195 | BEGIN                                         |
| mysql-bin.000021 | 195 | Query       |         1 |         298 | insert into test.t1 values(1,'a')             |
| mysql-bin.000021 | 298 | Xid         |         1 |         329 | COMMIT /* xid=25 */                           |
| mysql-bin.000021 | 329 | Query       |         1 |         408 | BEGIN                                         |
| mysql-bin.000021 | 408 | Query       |         1 |         515 | use `test`; insert into test.t1 values(2,'b') |
| mysql-bin.000021 | 515 | Xid         |         1 |         546 | COMMIT /* 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
# :: server id   end_log_pos  CRC32 0x03010da1     Start: binlog v , server v 5.6.-log created  ::
# Warning: this binlog is either in use or was not closed properly.

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         |
...

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：

mysql> show binlog events in 'mysql-bin.000027';
+------------------+-----+-------------+-----------+-------------+---------------------------------------+
| Log_name         | Pos | Event_type  | Server_id | End_log_pos | Info                                  |
+------------------+-----+-------------+-----------+-------------+---------------------------------------+
| mysql-bin.000027 |   4 | Format_desc |         1 |         120 | Server ver: 5.6.31-log, Binlog ver: 4 |
| mysql-bin.000027 | 120 | Query       |         1 |         188 | BEGIN                                 |
| mysql-bin.000027 | 188 | Table_map   |         1 |         236 | table_id: 80 (test.t1)                |
| mysql-bin.000027 | 236 | Write_rows  |         1 |         278 | table_id: 80 flags: STMT_END_F        |
| mysql-bin.000027 | 278 | Xid         |         1 |         309 | COMMIT /* xid=198 */                  |
| mysql-bin.000027 | 309 | Query       |         1 |         377 | BEGIN                                 |
| mysql-bin.000027 | 377 | Table_map   |         1 |         425 | table_id: 80 (test.t1)                |
| mysql-bin.000027 | 425 | Update_rows |         1 |         475 | table_id: 80 flags: STMT_END_F        |
| mysql-bin.000027 | 475 | Xid         |         1 |         506 | COMMIT /* xid=199 */                  |
| mysql-bin.000027 | 506 | Query       |         1 |         574 | BEGIN                                 |
| mysql-bin.000027 | 574 | Table_map   |         1 |         622 | table_id: 80 (test.t1)                |
| mysql-bin.000027 | 622 | Delete_rows |         1 |         664 | table_id: 80 flags: STMT_END_F        |
| mysql-bin.000027 | 664 | Xid         |         1 |         695 | COMMIT /* 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。

mysql> show binlog events in 'mysql-bin.000028';
+------------------+-----+-------------+-----------+-------------+---------------------------------------+
| Log_name         | Pos | Event_type  | Server_id | End_log_pos | Info                                  |
+------------------+-----+-------------+-----------+-------------+---------------------------------------+
| mysql-bin.000028 |   4 | Format_desc |         1 |         120 | Server ver: 5.6.31-log, Binlog ver: 4 |
| mysql-bin.000028 | 120 | Rotate      |         1 |         167 | mysql-bin.000029;pos=4                |
+------------------+-----+-------------+-----------+-------------+---------------------------------------+
2 rows in set (0.00 sec)

# at
# :: server id   end_log_pos  CRC32 0xd965567c     Rotate to mysql-bin.  pos: 

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
#  :: server id   end_log_pos  CRC32 0xaeb24aac     GTID [commit=yes]
SET @@SESSION.GTID_NEXT= 'cad449f2-5d4f-11e6-b353-000c29c64704:3'/*!*/;
# at
#  :: server id   end_log_pos  CRC32 0x042ca092     Query    thread_id=    exec_time=    error_code=
SET TIMESTAMP=/*!*/;
BEGIN
/*!*/;
# at
#  :: server id   end_log_pos  CRC32 0xa35beb37     Query    thread_id=    exec_time=    error_code=
SET TIMESTAMP=/*!*/;
insert into test.t1 values(,'b')
/*!*/;
# at
#  :: server id   end_log_pos  CRC32 0x1905d8c6     Xid =
COMMIT/*!*/;

mysql> show binlog events in 'mysql-bin.000033';
+------------------+-----+----------------+-----------+-------------+-------------------------------------------------------------------+
| Log_name         | Pos | Event_type     | Server_id | End_log_pos | Info                                                              |
+------------------+-----+----------------+-----------+-------------+-------------------------------------------------------------------+
| mysql-bin.000033 |   4 | Format_desc    |         1 |         120 | Server ver: 5.6.31-log, Binlog ver: 4                             |
| mysql-bin.000033 | 120 | Previous_gtids |         1 |         191 | cad449f2-5d4f-11e6-b353-000c29c64704:1                            |
| mysql-bin.000033 | 191 | Gtid           |         1 |         239 | SET @@SESSION.GTID_NEXT= 'cad449f2-5d4f-11e6-b353-000c29c64704:2' |
| mysql-bin.000033 | 239 | Query          |         1 |         314 | BEGIN                                                             |
| mysql-bin.000033 | 314 | Query          |         1 |         417 | insert into test.t1 values(1,'a')                                 |
| mysql-bin.000033 | 417 | Xid            |         1 |         448 | COMMIT /* xid=11 */                                               |
| mysql-bin.000033 | 448 | Gtid           |         1 |         496 | SET @@SESSION.GTID_NEXT= 'cad449f2-5d4f-11e6-b353-000c29c64704:3' |
| mysql-bin.000033 | 496 | Query          |         1 |         571 | BEGIN                                                             |
| mysql-bin.000033 | 571 | Query          |         1 |         674 | insert into test.t1 values(2,'b')                                 |
| mysql-bin.000033 | 674 | Xid            |         1 |         705 | COMMIT /* xid=12 */                                               |
| mysql-bin.000033 | 705 | Rotate         |         1 |         752 | mysql-bin.000034;pos=4                                            |
+------------------+-----+----------------+-----------+-------------+-------------------------------------------------------------------+
11 rows in set (0.00 sec)

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：

mysql> show binlog events in 'mysql-bin.000033';
+------------------+-----+----------------+-----------+-------------+-------------------------------------------------------------------+
| Log_name         | Pos | Event_type     | Server_id | End_log_pos | Info                                                              |
+------------------+-----+----------------+-----------+-------------+-------------------------------------------------------------------+
| mysql-bin.000033 |   4 | Format_desc    |         1 |         120 | Server ver: 5.6.31-log, Binlog ver: 4                             |
| mysql-bin.000033 | 120 | Previous_gtids |         1 |         191 | cad449f2-5d4f-11e6-b353-000c29c64704:1                            |
| mysql-bin.000033 | 191 | Gtid           |         1 |         239 | SET @@SESSION.GTID_NEXT= 'cad449f2-5d4f-11e6-b353-000c29c64704:2' |
| mysql-bin.000033 | 239 | Query          |         1 |         314 | BEGIN                                                             |
| mysql-bin.000033 | 314 | Query          |         1 |         417 | insert into test.t1 values(1,'a')                                 |
| mysql-bin.000033 | 417 | Xid            |         1 |         448 | COMMIT /* xid=11 */                                               |
| mysql-bin.000033 | 448 | Gtid           |         1 |         496 | SET @@SESSION.GTID_NEXT= 'cad449f2-5d4f-11e6-b353-000c29c64704:3' |
| mysql-bin.000033 | 496 | Query          |         1 |         571 | BEGIN                                                             |
| mysql-bin.000033 | 571 | Query          |         1 |         674 | insert into test.t1 values(2,'b')                                 |
| mysql-bin.000033 | 674 | Xid            |         1 |         705 | COMMIT /* xid=12 */                                               |
| mysql-bin.000033 | 705 | Rotate         |         1 |         752 | mysql-bin.000034;pos=4                                            |
+------------------+-----+----------------+-----------+-------------+-------------------------------------------------------------------+
11 rows in set (0.00 sec)

mysql> show binlog events in 'mysql-bin.000034';
+------------------+-----+----------------+-----------+-------------+------------------------------------------+
| Log_name         | Pos | Event_type     | Server_id | End_log_pos | Info                                     |
+------------------+-----+----------------+-----------+-------------+------------------------------------------+
| mysql-bin.000034 |   4 | Format_desc    |         1 |         120 | Server ver: 5.6.31-log, Binlog ver: 4    |
| mysql-bin.000034 | 120 | Previous_gtids |         1 |         191 | cad449f2-5d4f-11e6-b353-000c29c64704:1-3 |
+------------------+-----+----------------+-----------+-------------+------------------------------------------+
2 rows in set (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
#  :: server id   end_log_pos  CRC32 0x4e84f3b5     Previous-GTIDs
# cad449f2-5d4f-11e6-b353-000c29c64704:-

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：

mysql> show binlog events in 'mysql-bin.000030';
+------------------+-----+-------------+-----------+-------------+---------------------------------------+
| Log_name         | Pos | Event_type  | Server_id | End_log_pos | Info                                  |
+------------------+-----+-------------+-----------+-------------+---------------------------------------+
| mysql-bin.000030 |   4 | Format_desc |         1 |         120 | Server ver: 5.6.31-log, Binlog ver: 4 |
| mysql-bin.000030 | 120 | Stop        |         1 |         143 |                                       |
+------------------+-----+-------------+-----------+-------------+---------------------------------------+
2 rows in set (0.04 sec)

# at
#  :: server id   end_log_pos  CRC32 0xf20ddc85     Stop

参考

1. MariaDB原理与实现

2. MySQL官方文档