0

Is there a more up-to-date specification for MySQL's .frm files than the one on dev.mysql.com? I'm trying to parse it manually (don't ask... just experimenting; not trying to recover anything).

The first part on "Table 11.1 .frm File Header Section" mostly matches up, but after that I'm not sure what to do.

"Table 11.2 .frm File Key Information Section" says the "Name of engine" is at 0x101a, but I'm finding "InnoDB" at 0xAA39 in my .frm file. I'm guessing those offsets aren't actually exact, and they depend the number of indexes and such.

How can I figure out the actual offset for where the "Table 11.4 .frm File Column Information Section" begins?

Improve this question
3
  • Looking toward the future: In 8.0, .frm files are gone.
    – Rick James
    Commented Jun 3, 2018 at 23:12
  • @RickJames 8.0 also has significantly improved the performance of information schema hasn't it? I wouldn't be fiddling with .frm files if 5.6 wasn't so darn slow :-(
    – mpen
    Commented Jun 4, 2018 at 18:00
  • Seemingly 'infinite' speedup.
    – Rick James
    Commented Jun 4, 2018 at 21:30

2 Answers 2

Reset to default
3

This is bit late but in case anyone is still interested.....

I have been helping a student to write a program (in PHP!) to recreate the CREATE TABLE statement that is implicit in mySQL .frm files, by attempting t parse the .frm files directly. (yes we know it can be done with various tools!!).

It was very difficult to track down the structure of the file and what is available at the site reference by mpen above is incomplete and sometimes incorrect.

Eventually I was able to track down the source code for mysqlfrm.exe and from there I located the particular class file that does the .frm file parse. It is written in Python, which is very readable - even if you dot know the language.

I was able to use this file (apart from a few minor corrections) to work out the indices in the .frm file where everything is stored and how to recover the various fields.

Here is the link...

http://www.commongrounds.co.uk/Library/lib/python2.7/site-packages/mysql/utilities/common/?DA and the required file is aptly names frm_reader.py/

Let it not be said that the .frm file format is forgotten!!

Improve this answer
3
  • @akuzminsky see above I came across mpen's questions and your reply.
    – bcperth
    Commented Aug 19, 2018 at 23:34
  • @mpen see above I came across your questions and akuzminsky's reply.
    – bcperth
    Commented Aug 19, 2018 at 23:35
  • It is very impressive work! +1.
    – akuzminsky
    Commented Aug 31, 2018 at 15:51
1

I don't think anybody knows .frm format even in Oracle. Because if you play with mysqlfrm you will notice that it actually starts mysqld to read an .frm file.

From what I remember, columns are listed in the end of the file. strings tbl.frm will show them. Obviously these are just column names, not full info.

Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.