[mythtv] Why MythTV didn't handle the UK Freeview lineup change

John Barberio barberio at lineone.net
Sun Jul 26 17:23:46 UTC 2009

Stuart Morgan wrote:
> On Sunday 26 Jul 2009 17:37:27 John Barberio wrote:
> > The problem here is that on MythTV, a rescan didn't work.
> >
> > Deleting the channel, and doing a rescan didn't work.
> >
> > Deleting all the channels, and doing a rescan didn't work.
> >
> > The only way to get 'Virgin 1' and 'Virgin +1' in the right channels
> > was to delete all channels, force a database sync by running
> > mythfilldatabase from the command line, and then do a rescan.
> See this is the problem, it just does not work that way.  
> Mythfilldatabase has
> nothing to do with scanning or 'database syncs' as you call it. You're
> mistaken but won't accept that this is the case. Deleting channels  
> would have
> worked, it immediately removes the channels from the database.
> I don't know how to explain the behaviour you report above but to  
> suggest user
> error.

And yet, this was the behaviour I saw.

The exact same behaviour described by another user here - http://www.gossamer-threads.com/lists/mythtv/users/383253

I don't see much leway for 'user error' here. The 'deleted channel'  
kept getting recreated, until mythfilldatabase was run after the  
delete operation. And it looks very much like a 'dirty cache' problem  
to me. There may well be some user setting in the mysql server on my  
end that causes the table to be cached, that doesn't happen on yours.  
It may be that this bug only gets exposed with mysql servers set up in  
a specific way. But it's still a bug seen by two different people, who  
could work-around it the same way with the same results, and with the  
same very simple fix of ensuring the database consistency when doing a  
scan, and perhaps offering a 'delete all channels and rescan' option  
to assist for future lineup changes.

Generally, any programer should be wary of declaring 'it just does not  
work that way'. Perhaps you meant 'it should not work that way', since  
apparently it has. As an aside, this very much reminds me of the  
Source Engine stutter bug which 'just does not work that way', fixed  
only after they realised their QA test boxes were all vanilla XP, and  
none had 'Asian Language Support' enabled.

   - John

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