Thava's Blog
Thava Alagu focuses on database technologies and works for database group, at Sun Microsystems, Bangalore, India.
He has over 14 years of experience in software industry with various technologies, such as device drivers, hardware diagnostics, medical applications, systems security apart from databases technologies. Here after, he promises that he will not refer to himself in 3rd person in this blog.
My interests include MySQL, PHP, Web 2.0, J2EE and philosophy, art of living, yoga and history.
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How to dump mysql table definition file header
If you decide to copy over one table from MySQL installation to another installation, this could be done as simple as copying over your-table-name.* in data directory. Ofcourse, to do this, the database should not be running at the time of copying.
For example, for tables created by MyISAM storage engine, the files to be copied for table mytable are mytable.frm, mytable.MYD and mytable.MYI. The ".frm" file contains table definition, the ".MYI" contains info about index and ".MYD" contains data.
If you do this kind of stuff often, you may want to dump the header of the ".frm" header file. I just wrote a script for this. You can download this php script "frmdump" from here. Note that it is a php script, but meant to be run from command line (not to be used as web page) :
$ ./frmdump mytable.frm
Dumping mytable.frm using .frm header format ...
OFFSET |Len| Expected | Found | Comments
(Dec) | | (Hex) | (Hex) |
-----------------------------------------------
0 | 2 | FE 01 | fe 01 | Magic mark. 0xFE 01
2 | 1 | 09 | 09 | FRMVER + 3 + VarcharInTab?1:0
3 | 1 | 09(MyISAM)| 09 | Found type: DB_TYPE_MYISAM
4 | 1 | ?? | 03 | ??
5 | 1 | 0 | 00 | Always 0
6 | 2 | 00 10 | 00 10 | IO_SIZE 4096(dec)is 0x1000(LittleEnd)
8 | 2 | 01 00 | 01 00 | ???
* | * | ....... | ...... | .......
33 | 1 | 05 | 05 | Marked 5 for Ver5 FRM File
38 | 1 | 08? 2e? | 2e | default charset num for this table.
| 08 is latin1 default. 2e is utf8_bin
51 | 4 | Version | 00ea66 | MySQL Version ID Found: Dec: 60006
Just notice the 4 bytes at offset 51. That is the MySQL version ID that created this .frm file! The decimal 60006 indicates that this is 6.0.6 (it is now alpha) release.
If you want to know more about the file format you can check out this link
Posted at 08:10PM Aug 01, 2008 by thava in MySQL | Comments[4]
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If you want to contact me, please send email to thavamuni (dot) alagu (at) sun (dot) com.
