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How can i be sure my Dropped table still exist or it's overwritten?

  1. Backup and Data Recovery for MySQL
  2. How can i be sure my Dropped table still exist or it's overwritten?
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Hello there.

I can easily find some of my lost table’s records

Exact deleted record by mixing two adjacent col’s record

# grep -a exact_deleted_record disk.img
...
.......exact_deleted_record ........ printed

Also search for match :

# grep -r exact_deleted_record disk.img
Binary file disk.img matches

But after last step of parsing data (As blog posts) again i used grep for that records by using grep deleted_record dumps/default/users

But result is empty ! 🙁

I should notice that I checked all of possible tables that exist inside 00000000001.page
And just one of tables had a primary keys there.
So i’m sure that i have not any other table to recover inside log.

So to make sure to do steps again and again please first tell me , Even after i see my record inside disk image (by grep) is it possible that my data is not recoverable ?

    • Guest
    • 1 year ago
    Do you get any matches when you run `grep -r deleted_record pages-disk.img`?
  • mark.aragon
    Yes , even i can see that row completely by -a option——–i Updated question— You can check the question again to see the bash result.
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There is a number of scenarios when grep shows matches but a record eventually isn’t recovered. I’ll list them however there is not enough information on what’s the case here.

1. The matching pattern is found somewhere else, not in the PRIMARY index. It can be the REDO log, Undo segment, secondary index. The c_parser tool can extract records from pages of the PRIMARY index, everything else need fine tuning and I doubt an average user can do it.

2. The matching pattern is in the PRIMARY index, but the record in question is either heavily damaged or data filters skip this record.

3. The stream_parser tool skips the page with the record in question. That can happen because stream_parser itself does some initial page consistency checks and if a page is heavily damaged stream_parser may skip it.

4. Bugs. No software is bugless and recovering deleted or corrupted tables is very difficult problem.

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