[mythtv-users] partial database restore

UB40D ub40dd at googlemail.com
Tue Sep 17 16:45:53 UTC 2013


On Tue, Sep 17, 2013 at 3:18 PM, Michael T. Dean <mtdean at thirdcontact.com>wrote:

>
> 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


Thanks, I'll try that.


> 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.


Thanks.
I'm not sure if even now I have enough knowledge to configure things
"properly" though ;-)

For example in the new reinstall, at the end of scanning for channels (the
operation that lasts 15-20 mins) it said things along the lines of "I found
[duplicate/unrecognized/new/conflicting] channels, what now?" and I had no
real clue what the message meant nor what the correct answer might be. I
thought I picked the sensible option (no duplicates etc) but this morning I
found that, when scheduling new recordings,
- in the channel listing I have only one BBC ONE HD, and it has no program
data whatsoever; but
- in the "grid" tv schedule I have two BBC ONE HD, one of which is empty
and the other one with data.
Go figure...

I think in this instance the program isn't too helpful when it comes to
explaining what the problem it encounters is, nor when it comes to
explaining what the options on offer will do. And, if you guess and try one
just to move along, there's no undo, short of starting it all again.

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.
>

This reiterates the wisdom of the mythbackup/restore page. It appears to
mean that unfortunately there's no supported way of exporting recordings
from a myth system and importing them into another, which would in many
cases be desirable.


> 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 ).
>

I'd be more than happy to do that if I could transcode them losslessly (so
that the parts described by the cut list are preserved and the others
thrown away, and the subtitles are preserved), which would finally make the
edited .mpg files independent of the database and thus portable and robust
to crashes. However in previous years I have tried this many times (and
also asked here) and never got anywhere. Is this now possible? If so,
that's really good news.

What you describe in the link makes the video library sound very appealing,
especially if I can define a directory structure over the archived films.
Willing to give it a try. Pity to lose the descriptions from EIT,
though---they're kind of useful when browsing.

Thanks for all your suggestions and special thanks for the references to
specific useful messages I hadn't found on my own when googling through the
list archives.
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