[mythtv-users] partial database restore
Michael T. Dean
mtdean at thirdcontact.com
Tue Sep 17 14:18:35 UTC 2013
On 09/16/2013 07:11 PM, UB40D wrote:
> Restoring only the useful parts of a database
>
> I had a mythbuntu system that would often give "recorder failed" and
> litter the media library with 4 identical entries of the failed
> recording, each with "this file cannot be found" if you selected it,
> which were a pain to delete. Since I was not able to fix the issue, I
> decided to reinstall everything from zero on a new hard disk. I did
> take a backup of the database before reinstalling.
>
> I would now like to restore the old recordings (the ones that work)
> and their metadata. In particular what I'd like is, for each .mpg, its
> name, description and the manually-entered cut list that defines the
> ads to be skipped. I don't terribly mind losing the date that the
> shows were recorded or the channel they came from, but I would very
> much mind losing the cut lists and of course the film names, which I
> understand would happen if I just copied the mpgs into the video
> directory.
>
> However I don't really want to restore all of the old database which
> is full of that junk (empty entriesfor orphaned recordings
> that never happened).
http://www.mythtv.org/wiki/Find_orphans.py
> I am also suspicious that the
> faulty behaviour of the old system was perhaps due to
> slightly incorrect backend configuration (channels, capture cards,
> video sources, input connections etc) that might be stored in the
> database as well; I don't want to overwrite the new ones of the
> reinstalled system that finally work with the old ones that didn't.
There's definitely no support, whatsoever, for "merging" data from
multiple databases.
If your input connections configuration (which entails everything you
mentioned, above) is broken, you can clear it (completely--as if you
were starting with a brand-new, empty database) with "Delete all video
sources" and "Delete all capture cards" (not "Delete all capture cards
on <hostname>").
http://www.gossamer-threads.com/lists/mythtv/users/264034#264034
Then, it's just a matter of (using the knowledge gained when you
configured it properly, this time), reconfiguring it properly.
> I have read
> http://www.mythtv.org/wiki/Database_Backup_and_Restore#Change_the_hostname_of_a_MythTV_frontend_or_backend
> and noticed their insistence on how bad a partial restore is, and that a
> full restore is what every sane person should do. However I fear that
> if I do a full restore I'll end up with as broken a system as the one I had
> before reinstalling.
>
> I would simply like to restore the names and cut lists of the .mpgs
> that I have. Nothing else. Can I? What should I do? Is it OK to take the
> database dump and, before importing it, delete everything except the
> statements for the tables that contain the names and cut lists?
>
Cutting out parts of the database backup and sticking them into a
different database is akin to grabbing bytes within a Word document and
sticking them into another. It's not the recommended approach for
editing, and it requires learning the data constraints/format/language
completely. It may or may not work, and may cause problems that are
only visible days/weeks/months down the line.
A partial restore is only useful for fixing a corrupt schema or for
getting rid of untrusted/corrupt data (and, really, only if that data
exists in certain tables). And, a partial restore can only be performed
on an empty database. Any other "manual" partial restore is likely to
cause data integrity problems that may well create more problems than
getting rid of your old database "solved"--especially when there are
good ways to clean up orphaned recordings (file and/or metadata) and bad
configuration in your old database.
If you have some new recordings on the new system, your best bet for
them will be to put them into the managed-by-the-user video section, the
Video Library (and you may even want to consider doing the same for any
other recordings you may want to keep -
http://www.gossamer-threads.com/lists/mythtv/users/519758#519758 ).
Mike
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