MySQL通过binlog来记录整个数据的变更过程,因此我们只要有MySQL的binlog日志即可完整的还原。MySQL binlog日志记录有3种不同的方式,即:STATEMENT,MIXED,ROW。对于不同的日志模式,生成的binlog有不同的记录方式。对于MIXED(部分SQL语句)和ROW模式是以base-64方式记录,会以BINLOG开头,是一段伪SQL,我们可以用使用base64-output参数来抑制其显示。本文对此给出了描述及演示。

有关binlog的用法,请参考:使用mysqlbinlog提取二进制日志

 

1、mysqlbinlog之base64-output参数

--base64-output=value

This option determines when events should be displayed encoded as base-64 strings using BINLOG statements. The option has these permissible values (not case sensitive):

AUTO ("automatic") or UNSPEC ("unspecified") displays BINLOG statements automatically when necessary (that is, for format description events and row events). If no --base64-output option is given, the effect is the same as --base64-output=AUTO. NEVER causes BINLOG statements not to be displayed. mysqlbinlog exits with an error if a row event is found that must be displayed using BINLOG.DECODE-ROWS specifies to mysqlbinlog that you intend for row events to be decoded and displayed as commented SQL statements by also specifying the --verbose option. Like NEVER, DECODE-ROWS suppresses display of BINLOG statements, but unlike NEVER, it does not exit with an error if a row event is found.

以上描述对于binlog日志中的BINLOG部分,如果要过虑掉需要指定DECODE-ROWS 以及--verbose选项。

 

The SQL statements produced by --verbose for row events are much more readable than the corresponding BINLOG statements. However, they do not correspond exactly to the original SQL statements that generated the events. The following limitations apply:

--verbose选项可以获取更多的可读信息,但是并不是一个原始的SQL语句(类似的)。

· The original column names are lost and replaced by @N, where N is a column number.

· Character set information is not available in the binary log, which affects string column display:

There is no distinction made between corresponding binary and nonbinary string types (BINARY and CHAR,VARBINARY and VARCHAR, BLOB and TEXT). The output uses a data type of STRING for fixed-length strings andVARSTRING for variable-length strings.For multibyte character sets, the maximum number of bytes per character is not present in the binary log, so the length for string types is displayed in bytes rather than in characters. For example, STRING(4) will be used as the data type for values from either of these column types:

CHAR(4) CHARACTER SET latin1

CHAR(2) CHARACTER SET ucs2

Due to the storage format for events of type UPDATE_ROWS_EVENT, UPDATE statements are displayed with theWHERE clause preceding the SET clause.

Proper interpretation of row events requires the information from the format description event at the beginning of the binary log. Because mysqlbinlog does not know in advance whether the rest of the log contains row events, by default it displays the format description event using a BINLOG statement in the initial part of the output.

If the binary log is known not to contain any events requiring a BINLOG statement (that is, no row events), the --base64-output=NEVER option can be used to prevent this header from being written.

 

2、演示生成binlog日志

--环境
mysql> show variables like 'version';
+---------------+------------+
| Variable_name | Value      |
+---------------+------------+
| version       | 5.6.12-log |
+---------------+------------+

--如下查询binlog为row记录模式
mysql> show variables like 'binlog_for%';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| binlog_format | ROW   |
+---------------+-------+

mysql> reset master;
Query OK, 0 rows affected (0.01 sec)

mysql> show master status;
+-----------------+----------+--------------+------------------+-------------------+
| File            | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+-----------------+----------+--------------+------------------+-------------------+
| APP01bin.000001 |      120 |              |                  |                   |
+-----------------+----------+--------------+------------------+-------------------+

mysql> use test;
Database changed

--创建表t1
mysql> create table t1(id smallint,val varchar(20));
Query OK, 0 rows affected (0.01 sec)

--插入单条记录
mysql> insert into t1 values(1,'robin');
Query OK, 1 row affected (0.00 sec)

--清空表
mysql> truncate table t1;
Query OK, 0 rows affected (0.01 sec)

--查看binlog events
mysql> show binlog events;
+-----------------+-----+-------------+-----------+-------------+----------------------------------------------------------+
| Log_name        | Pos | Event_type  | Server_id | End_log_pos | Info                                                     |
+-----------------+-----+-------------+-----------+-------------+----------------------------------------------------------+
| APP01bin.000001 |   4 | Format_desc |        11 |         120 | Server ver: 5.6.12-log, Binlog ver: 4                    |
| APP01bin.000001 | 120 | Query       |        11 |         238 | use `test`; create table t1(id smallint,val varchar(20)) |
| APP01bin.000001 | 238 | Query       |        11 |         310 | BEGIN                                                    |
| APP01bin.000001 | 310 | Table_map   |        11 |         358 | table_id: 74 (test.t1)                                   |
| APP01bin.000001 | 358 | Write_rows  |        11 |         402 | table_id: 74 flags: STMT_END_F                           |
| APP01bin.000001 | 402 | Xid         |        11 |         433 | COMMIT /* xid=30 */                                      |
| APP01bin.000001 | 433 | Query       |        11 |         517 | use `test`; truncate table t1                            |
+-----------------+-----+-------------+-----------+-------------+----------------------------------------------------------+
7 rows in set (0.00 sec)

--获取binlog位置
mysql> show variables like 'log_bin_basename';
+------------------+--------------------+
| Variable_name    | Value              |
+------------------+--------------------+
| log_bin_basename | /opt/data/APP01bin |
+------------------+--------------------+

3、演示提取binlog日志

BINLOG ' #这个BINLOG部分是真实的SQL语句,无法看到具体内容<br >fzcsvbmlaaaamaaaagybaaaaaeoaaaaaaaeabhrlc3qaanqxaaicdwi8aameualg<br="" >fzcsvb4laaaalaaaajibaaaaaeoaaaaaaaeaagac="" wbaavyb2jpbv7cujq="<br" >'="" *!*="" ;

#使用-v参数的情形,可以看到我们操作生成的SQL语句了,为insert into ..@1之类的形式,如果-vv则输出列的描述信息

BINLOG '<br >fzcsvbmlaaaamaaaagybaaaaaeoaaaaaaaeabhrlc3qaanqxaaicdwi8aameualg<br="" >fzcsvb4laaaalaaaajibaaaaaeoaaaaaaaeaagac="" wbaavyb2jpbv7cujq="<br" >'="" *!*="" ;

#添加--base64-output=DECODE-ROWS选项来抑制BINLOG的显示,如下我们看不到了BINLOG部分

#此时使用mysqlbinlog做一个不完全恢复

#查看恢复后的结果