[mythtv-users] 0.25 SQL CPU Load issues after optimisation

Another Sillyname anothersname at googlemail.com
Mon Jul 23 15:14:39 UTC 2012

On 23 July 2012 15:02, Michael T. Dean <mtdean at thirdcontact.com> wrote:
> On 07/21/2012 06:24 AM, Mike Perkins wrote:
>> On 20/07/12 22:54, Another Sillyname wrote:
>>> I cleaned up the rules and while doing so came across something that
>>> could be a conflict.
>>> When I originally built the system as a combined Freeview and Freesat
>>> service the CHANID values get set according to the order that the
>>> source device is chosen.
>>> In my original build I'd actually scanned the DVB-T channels twice
>>> from two different DVB-T tuners as I didn't realise that the source
>>> could be shared by the other tuners.  So then when I scanned the DVB-S
>>> channels there was a 4000 offset for the SID and therefore CHANID, for
>>> example BBC HD which has a SID of 6940 got allocated a CHANID of 10940
>>> to allow for the offset.
>>> When I did the recent rebuild I didn't make the same error so the SID
>>> and CHANID were instead 8940 rather then the original 10940.  This
>>> means the database had recording rules for CHANID values that just
>>> didn't exist in the database anymore.
>>> I've cleaned the rules down from 750+ to about 150 and will monitor
>>> for a few more days, if I'm right it'll be worth putting this into the
>>> wiki so it doesn't catch out other users later.
>>> Fingers crossed but good job guys.
>> That raises an important question that wouldn't have bothered us in the
>> old analog days.
>> In the digital world, channels are getting moved about on a fairly
>> frequent basis which means we end up rescanning more than we used to. End
>> result: CHANID for any particular channel can get changed from time to time.
>> This means that "record on channel xxx" rules are likely not going to work
>> after a scan. I have some of these, and they are a pain to try and figure
>> out which channel they referred to, as they display as "Record on channel ."
>> - that is, the history is gone.
> Yes, this is why "this channel" rules are generally discouraged--because
> they require you to re-create the rules after any changes to your channels.
>> Is there any chance that in the future these rules won't be tied to CHANID
>> but some other identifier like CALLSIGN, perhaps? (Remembering for those of
>> you in the US that CALLSIGN can be a /lot/ longer than 5-6 characters
>> elsewhere in the world.) Not necessarily CALLSIGN itself, perhaps, but a
>> uniqueid indexed on CALLSIGN.
> FWIW, they are tied to callsign--the callsign of the channel referenced by
> the given ID.  Note, also, that on rescanning it's /quite/ common for
> callsign to change, too--so changing the code/DB to reference callsign or
> station would only trade one problem for another, and you'd almost
> definitely have to keep re-creating any "this channel" rules.
> "Any channel" rules work before and after rescans, regardless of what
> changes.
> Mike
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The other side of the equation is that "record on any channel" can be
a problem where you have multiple similar channels....

For example in the UK you can have...

BBC 1 Scotland
BBC 1 Wales
BBC 1 Northern Ireland
301 Red Button Sports Event


Channel 4
Channel 4 +1 - 1 Hour timeshift
Channel 4 HD
More 4
More 4 +1

In the BBC case 95% of the programming is identical but sometimes a
sports event will only be covered on the regional channel, say for
example a Scottish football game would only be on BBC Scotland.

During the Olympics the BBC are also transmitting on an extra 20
channels for Olympics coverage - No that's not a typo it's an extra 20

In the case of Channel 4 programmes shown on Channel 4 will be
simulshown on the HD version and shown on the +1 channel an hour
later.  They can also be shown later that week on the More 4 channel,
usually with the same PROGID but occasionally a different PROGID.

So mythweb can become incredibly cluttered with non recording versions
of a program if you don't use the 'record on this channel only'

I appreciate what you're saying but please don't think people aren't
having to use 'this channel only' for a reason.

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