【MySQL】frm⽂件解析frm是MySQL表结构定义⽂件，通常frm⽂件是不会损坏的，但是如果出现特殊情况出现frm⽂件损坏也不要放弃希望，例如下⾯报错：15082116:31:27[ERROR]/usr/local/mysql51/libexec/mysqld: Incorrect information in file: './t/test1.frm'
当修复MyISAM和InnoDB表时，MySQL服务会⾸先去调⽤frm⽂件，所以我们只能通过修复frm⽂件进⾏后⾯的数据恢复。
MySQL通过的create_frm()函数创建frm⽂件，创建出来的frm⽂件是⼆进制⽂件，需要通过hexdump解析成16进制来分析。create_frm()函数对frm⽂件头部定义的代码
/* Create a .frm file */
File create_frm(THD *thd, const char *name, const char *db,
const char *table, uint reclength, uchar *fileinfo,
HA_CREATE_INFO *create_info, uint keys, KEY *key_info)
{
register File file;
ulong length;
uchar fill[IO_SIZE];
int create_flags= O_RDWR | O_TRUNC;
ulong key_comment_total_bytes= 0;
uint i;
if (create_info->options & HA_LEX_CREATE_TMP_TABLE)
create_flags|= O_EXCL | O_NOFOLLOW;
/* Fix this when we have new .frm files; Current limit is 4G rows (QQ) */
if (create_info->max_rows > UINT_MAX32)
create_info->max_rows= UINT_MAX32;
if (create_info->min_rows > UINT_MAX32)
create_info->min_rows= UINT_MAX32;
if ((file= mysql_file_create(key_file_frm,
name, CREATE_MODE, create_flags, MYF(0))) >= 0)
{
uint key_length, tmp_key_length, tmp, csid;
bzero((char*) fileinfo,64);
/* header */
fileinfo[0]=(uchar) 254;
fileinfo[1]= 1;
fileinfo[2]= FRM_VER+3+ test(create_info->varchar);
fileinfo[3]= (uchar) ha_legacy_type(
ha_checktype(thd,ha_legacy_type(create_info->db_type),0,0));
fileinfo[4]=1;
int2store(fileinfo+6,IO_SIZE); /* Next block starts here */
/*
Keep in sync with pack_keys()
网络统考成绩查询For each key:
8 bytes for the key header
9 bytes for each key-part (MAX_REF_PARTS)
NAME_LEN bytes for the name
1 byte for the NAMES_SEP_CHAR (before the name)
For all keys:
6 bytes for the header
1 byte for the NAMES_SEP_CHAR (after the last name)
9 extra bytes (padding for safety? alignment?)
*/
for (i= 0; i < keys; i++)
{
DBUG_ASSERT(test(key_info[i].flags & HA_USES_COMMENT) ==
(key_info[i]ment.length > 0));
if (key_info[i].flags & HA_USES_COMMENT)
key_comment_total_bytes += 2 + key_info[i]ment.length;
}
key_length= keys * (8 + MAX_REF_PARTS * 9 + NAME_LEN + 1) + 16
+ key_comment_total_bytes;
length= next_io_size((ulong) (IO_SIZE+key_length+reclength+
create_info->extra_size));
int4store(fileinfo+10,length);
tmp_key_length= (key_length < 0xffff) ? key_length : 0xffff;
int2store(fileinfo+14,tmp_key_length);
int2store(fileinfo+16,reclength);
int4store(fileinfo+18,create_info->max_rows);
int4store(fileinfo+22,create_info->min_rows);
/* fileinfo[26] is set in mysql_create_frm() */
护士资格证考试可以考几次fileinfo[27]=2; // Use long pack-fields
/* fileinfo[28 & 29] is set to key_info_length in mysql_create_frm() */
create_info->table_options|=HA_OPTION_LONG_BLOB_PTR; // Use portable blob pointers
int2store(fileinfo+30,create_info->table_options);
fileinfo[32]=0; // No filename anymore
fileinfo[33]=5; // Mark for 5.0 frm file
int4store(fileinfo+34,create_info->avg_row_length);
csid= (create_info->default_table_charset ?
create_info->default_table_charset->number : 0);
fileinfo[38]= (uchar) csid;
/*
In future versions, we will store in fileinfo[39] the values of the
TRANSACTIONAL and PAGE_CHECKSUM clauses of CREATE TABLE.
*/
fileinfo[39]= 0;
fileinfo[40]= (uchar) create_info->row_type;
/* Next few bytes where for RAID support */
fileinfo[41]= (uchar) (csid >> 8);
fileinfo[42]= 0;
fileinfo[43]= 0;
fileinfo[44]= 0;
fileinfo[45]= 0;
fileinfo[46]= 0;
int4store(fileinfo+47, key_length);
tmp= MYSQL_VERSION_ID; // Store to avoid warning from int4store
int4store(fileinfo+51, tmp);
int4store(fileinfo+55, create_info->extra_size);
/*
59-60 is reserved for extra_rec_buf_length,
61 for default_part_db_type
*/
int2store(fileinfo+62, create_info->key_block_size);
bzero(fill,IO_SIZE);
for (; length > IO_SIZE ; length-= IO_SIZE)
{
if (mysql_file_write(file, fill, IO_SIZE, MYF(MY_WME | MY_NABP)))
{
(void) mysql_file_close(file, MYF(0));
(void) mysql_file_delete(key_file_frm, name, MYF(0));
国考行测真题百度云return(-1);
}
}
}
else
{
if (my_errno == ENOENT)
my_error(ER_BAD_DB_ERROR,MYF(0),db);
else
my_error(ER_CANT_CREATE_TABLE,MYF(0),table,my_errno);
}
return (file);
} /* create_frm */
View Code
open_binary_frm()函数对对frm索引部分定义的代码
for (i=0 ; i < keys ; i++, keyinfo++)
{
keyinfo->table= 0; // Updated in open_frm
if (new_frm_ver >= 3)
{
keyinfo->flags= (uint) uint2korr(strpos) ^ HA_NOSAME;
keyinfo->key_length= (uint) uint2korr(strpos+2);
keyinfo->key_parts= (uint) strpos[4];
keyinfo->algorithm= (enum ha_key_alg) strpos[5];
keyinfo->block_size= uint2korr(strpos+6);
strpos+=8;
}
else
{
keyinfo->flags= ((uint) strpos[0]) ^ HA_NOSAME;
keyinfo->key_length= (uint) uint2korr(strpos+1);
keyinfo->key_parts= (uint) strpos[3];
keyinfo->algorithm= HA_KEY_ALG_UNDEF;
strpos+=4;
}
keyinfo->key_part= key_part;
keyinfo->rec_per_key= rec_per_key;
国家公务员考试职位表2024for (j=keyinfo->key_parts ; j-- ; key_part++)
{
*rec_per_key++=0;
key_part->fieldnr= (uint16) (uint2korr(strpos) & FIELD_NR_MASK);
key_part->offset= (uint) uint2korr(strpos+2)-1;
key_part->key_type= (uint) uint2korr(strpos+5);
// key_part->field= (Field*) 0; // Will be fixed later
if (new_frm_ver >= 1)
{
key_part->key_part_flag= *(strpos+4);
key_part->length= (uint) uint2korr(strpos+7);
strpos+=9;
}
else
{
key_part->length= *(strpos+4);
key_part->key_part_flag=0;
if (key_part->length > 128)
{
key_part->length&=127; /* purecov: inspected */
2020年公务员录用公示key_part->key_part_flag=HA_REVERSE_SORT; /* purecov: inspected */
}
strpos+=7;
}
key_part->store_length=key_part->length;
}
}
keynames=(char*) key_part;
strpos+= (strmov(keynames, (char *) strpos) - keynames)+1;
//reading index comments
for (keyinfo= share->key_info, i=0; i < keys; i++, keyinfo++)
{
if (keyinfo->flags & HA_USES_COMMENT)
{
keyinfo->comment.length= uint2korr(strpos);
keyinfo->comment.str= strmake_root(&share->mem_root, (char*) strpos+2,
keyinfo->comment.length);
strpos+= 2 + keyinfo->comment.length;
}
DBUG_ASSERT(test(keyinfo->flags & HA_USES_COMMENT) ==
(keyinfo->comment.length > 0));
}
View Code
hexdump是Linux下的⼀个⼆进制⽂件查看⼯具，可以将⼆进制⽂件转换为ASCII、10进制、16进制或8进制进⾏查看。
hexdump 参数
-C 每⼀字节以16进制显⽰，⼀⾏共16个字节，显⽰⼗六进制存储的⽂本内容
-b 每⼀字节以⼋进制显⽰，⼀⾏共16个字节，⼀⾏开始以⼗六进制显⽰偏移值；
0000000 177 105 114 106 002 001 001 000 000 000 000 000 000 000 000 000
-c 每⼀字节以ASCII字符显⽰，其余同上；
0000000 177 E L F 002 001 001 \0 \0 \0 \0 \0 \0 \0 \0 \0
-n 只解释指定长度字节
单位：默认⼗进制，0x或0X开头则为16进制，0开头则为8进制。默认为字节，b则为512字节，k则为1024字节，m则为1048576字节-d 双字节⼗进制显⽰
-o 双字节⼋进制显⽰
-v 去除中间显⽰的“*”字符
-x 双字节⼗六进制显⽰
-e 格式化参数
实例版本与表字符集：
建表的实例版本0x033
语句hexdump -s 0x33 -n 2 -v -d table.frm
[root@test1 ~]# hexdump -s 0x33 -n 2 -v -d /data/3308/test/test1.frm
0000033 50153
0000035
所以版本为5.1.53，因为5.1/5.5和5.6在字段类型定义上有不同，所以确定好建表实例版本很重要，字段类型定义见下⾯
表字符集0x026
21=utf8
08=latin1
1c=GBK
语句hexdump -s 0x26 -n 1 table.frm
frm列属性：
1、列序号（初始列序号为4）
2、字段长度，整形长度
3、字段长度，latin1字符集字符类型长度，GBK字符集字符类型varchar长度*2，varchar(30)相当于就是60字节长度，换成16进制是3c，utf8字符集字符类型varchar长度*3，varchar(30)相当于就是90字节长度，换成16进制是5a
4、
5、
6、
7、
8、Flags for zerofill, unsigned, etc.(int 1b)
9、Additional flags,and scale if decimal/numeric(DEFAULT NULL 80,NOT NULL 40,DEFAULT 'VALUE' 00)
10、代码定义unireg_type，AUTO_INCREMENT of
11、
12、代码定义interval_nr
13、字段类型
14、字符集
15、备注长度
16、备注长度
字段类型（注意5.6版本字段类型有不同，会影响数据恢复）：
Data type for v5.1&v5.5 (v5.6)
fe=char
fa=mediumtext
f6=decimal
fc=text
of=varchar
01=tinyint
02=smallint
03=int
04=float
05=real
07=timestamp (v5.6 11=timestamp)
08=bigint
09=mediumint
10=bit
ob=time (v5.6 13=time)
oc=datetime (v5.6 12=datetime)
0d=year
0e=date
表中所含索引：
偏移量在0x1000之后的⼀段是frm索引部分，⽤hexdump -C打开后很容易到
0x1000：有⼏个索引
0x1001：全部索引包含⼏个字段
索引名是明⽂，具体索引结构见⽰例。
表：
CREATE TABLE `test3` (
`a` int(11) NOT NULL,
`b` varchar(10) DEFAULT NULL,
`c` int(11) NOT NULL,
PRIMARY KEY (`a`),
UNIQUE KEY `uniq_1` (`b`,`c`),
KEY `idx_1` (`c`,`b`),
KEY `idx_2` (`c`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
⼗六进制⽂件打开：
[root@test1 ~]# hexdump -C /data/3308/test/test3.frm
00000000 fe 01 0a 0c 03 00 00 10 01 00 00 30 00 00 74 05 |...........0..t.|
00000010 28 00 00 00 00 00 00 00 00 00 00 02 79 00 09 00 |(...........y...|
00000020 00 05 00 00 00 00 21 00 00 00 00 00 00 00 00 74 |......!........t| #表字符集
00000030 05 00 00 e9 c3 00 00 10 00 00 00 00 00 00 00 00 |................| #标红的是建表实例版本号
00000040 2f 2f 00 00 20 00 00 00 00 00 00 00 00 00 00 00 |//.. ...........|
00000050 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00001000 04 06 00 00 1d 00 00 00 04 00 01 00 00 00 01 80 |................|
00001010 02 00 00 1b 40 04 00 68 00 22 00 02 00 00 00 02 |....@..h."......|
00001020 80 06 00 00 00 80 1e 00 03 80 25 00 00 1b 40 04 |..........%...@.|
00001030 00 69 00 22 00 02 00 00 00 03 80 25 00 00 1b 40 |.i.".......%...@|
00001040 04 00 02 80 06 00 00 00 80 1e 00 01 00 04 00 01 |................|
00001050 00 00 00 03 80 25 00 00 1b 40 04 00 ff 50 52 49 |.....%...@...PRI|
00001060 4d 41 52 59 ff 75 6e 69 71 5f 31 ff 69 64 78 5f |MARY.uniq_1.idx_|
00001070 31 ff 69 64 78 5f 32 ff 00 00 00 00 00 00 00 00 |1.
00001080 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00001570 00 00 00 00 ff 00 00 00 00 00 00 00 00 00 00 00 |................|
00001580 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001590 00 00 00 00 00 00 00 00 00 00 00 00 00 00 06 00 |................|
000015a0 49 6e 6e 6f 44 42 00 00 00 00 00 00 00 00 00 00 |
000015b0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00002000 9a 01 00 10 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00002010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00002100 01 00 03 00 3f 00 34 00 00 00 28 00 08 00 00 00 |....?.4...(.....|
00002110 00 00 00 00 00 00 50 00 16 00 01 00 00 00 00 00 |......P.........|
00002120 3f 00 04 03 02 14 29 20 20 20 20 20 20 20 20 20 |?.....) |
00002130 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00002140 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 00 | .|
00002150 04 00 02 61 00 05 00 02 62 00 06 00 02 63 00 04 |...a....b....c..|
00002160 02 0b 0b 00 02 00 00 1b 40 00 00 00 03 3f 00 00 |........@....?..|
00002170 05 02 1e 1e 00 06 00 00 00 80 00 00 00 0f 21 00 |..............!.|
00002180 0006 02 0b 0b 00 25 00 00 1b 40 00 00 00 03 3f |......%...@....?|
00002190 0000 ff 61 ff 62 ff 63 ff 00 |...
通过上⾯的颜⾊区分，圈出的黄⾊部分是索引属性，下⾯红蓝绿三⾊是三列属性。
列属性结构：
红⾊部分：字段序号（4开始，4、5、6就是字段第⼀第⼆第三）
蓝⾊部分：字段长度
棕⾊部分：是否为空
绿⾊部分：字段类型
黄⾊部分：字符集
索引属性结构：
索引头部：
淡蓝⾊部分：索引统计数
粉⾊部分：索引总共有多少列
索引主体：
棕⾊部分：是否唯⼀索引
红⾊部分：表中列的序号
绿⾊部分：表中对应列的属性
字段默认值：
字段默认值不保存在字段属性中，⽽是保存在描述表引擎的那段中
int类型默认值保存为⼗六进制需转换⼗进制，char类型默认值保存为⼗六进制⽂本可通过hexdump -C直接看到
如果没有索引段则默认值在，0x1011后，如果有索引段，则位置顺延
例如表
CREATE TABLE `test1` (
`a` int(11) NOT NULL DEFAULT '2010',
吉林省公务员考试时间2023年`b` varchar(10) NOT NULL DEFAULT '2011' ,
`c` int(11) default '30',
`d` varchar(10) NOT NULL DEFAULT 'Yes'
)engine=innodb default charset=utf8;
*
00001000 00 00 00 00 02 00 ff 00 00 00 00 00 00 00 00 00 |................|
00001010 fe da 07 00 00 04 32 30 31 31 00 00 00 00 00 00 |......
00001020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001030 00 00 00 00 1e 00 00 00 03 59 65 73 00 00 00 00 |.........
00001040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001050 00 00 00 00 00 00 00 00 00 06 00 49 6e 6e 6f 44 |...........InnoD|
00001060 42 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |B...............|
00001070 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
column a:da 07 00 00
column b:04 32 30 31 31 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
column c:1e 00 00 00
column d:03 59 65 73 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
需要注意char字段的默认值是根据字段长度和字符集相关的，如上表varchar(10)，utf8是3bit，就是30个⼗六进制长度。
发布评论