Mysql – cannot recover thesql idb file

The very first thing to do is to make a copy of whatever data files you still have, and to keep it and any backups safe until long after your recovery effort is complete. Please read this (short) Wiki page:

http://wiki.postgresql.org/wiki/Corruption

Once you have done that, you can attempt various recovery strategies without fear that you will be worse off for the attempt, beyond the time required to try it. In general I recommend carefully following one of the techniques described in the documentation -- attempts to cut corners or to be creative often lead to corruption. Only a seasoned expert with a good understanding of PostgreSQL internals should attempt to deviate from the documented steps.

You didn't describe your backup strategy; details of what is available there may suggest alternatives you would not otherwise have.

Ultimately, if you have data of value which is not backed up, you may need to hand-edit the system tables to eliminate references to lost tablespace. This is not for the faint of heart. There are a number of companies with which you can contract for such services, many of whom have experience with recovery from catastrophic hardware failure like this.

http://www.postgresql.org/support/professional_support/

I am not affiliated with any of these companies.

Empty frm files won't work because they have a specific syntax which is being checked by mysql.

[root@server test]# touch test_one.frm
[root@server test]# chown mysql test_one.frm
[root@server test]# mysql test

Although it is showing up in show table because it only checks for the existence of the file ...

mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
....
| test_one       |
...
+----------------+

... any operations on it will fail.

mysql> show create table test_one;
ERROR 1033 (HY000): Incorrect information in file: './test/test_one.frm'

mysql> drop table test_one;
ERROR 1051 (42S02): Unknown table 'test.test_one'

The documentation says:

Create a matching .frm file in some other database directory and copy it to the database directory where the orphan table is located.

Now, matching (same structure) is actually not mandatory if you only want to drop it but you need to have a valid frm file.

If you do this you should be able to drop the table afterwards:

mysql> create table test_recoverer (id int unsigned primary key);
Query OK, 0 rows affected (0.31 sec)

[root@server test]# cat test_recoverer.frm > test_one.frm

mysql> drop table test_one;
Query OK, 0 rows affected (0.11 sec)