Retrieving Data from a crashed mysql table

Question

I am trying to retrieve some data from a mysql table that is marked as crashed. I am working on a restored backup of a machine, so I don't need to worry about anything.

When I try to mysqldump the table (FYI I am using --where to specify which records I need), I get an error:

mysqldump: Got error: 144: Table './[db]/[table]' is marked as crashed and last (automatic?) repair failed when doing LOCK TABLES

If I use --lock-tables=false I get the same error (but failed when doing SHOW FIELDS).

If I try to just SELECT the first record from the table I get the same error.

If I run CHECK TABLE [table], I get the following warnings/errors:

warning  | 1 client is using or hasn't closed the table properly |
warning  | Size of indexfile is: 1991678976      Should be: 1024 |
error    | Record-count is not ok; is 30030697   Should be: 0    |
warning  | Found 141967876 deleted space.   Should be 0          |
warning  | Found 3101578 deleted blocks       Should be: 0       |
warning  | Found 34721783 key parts. Should be: 0                |
error    | Corrupt                                               |

This implies that if I do a repair table, I will lose all the data! There should be 30030697 records there....

Is there any way for me to get to this data?

Answer 1

To repair the table in question issue the command

myisamchk --recover /var/lib/mysql/DATABASENAME/TABLE_NAME.myi

(Where DATABASENAME is the name of the database you are working with and TABLE_NAME is the name of the table to be checked.)

If this does not fully recover the table, you can re-run the command replacing –recover with –safe-recover which is slower and more thorough.

They only take a dump like that if there was some serious conflict during a row level lock, or bad write (bad sector).