[mythtv] Guide service API "Group By" usage

[Peter Bennett]

On 9/28/20 1:28 PM, Michael T. Dean wrote:
>
>> I am not sure if SQL will correctly group items that have null in 
>> their group by column.
>>
>> Should null channel numbers be allowed?
>
> The column is defined as NOT NULL:
>
> https://github.com/MythTV/mythtv/blob/master/mythtv/libs/libmythtv/dbcheck.cpp#L3894 
>
>
> and I don't see any changes anywhere that removed that restriction 
> (nor can I imagine changes that would do that).  Not sure what the 
> preferred approach is regarding coding to handle that invalid data 
> transparently or requiring valid data, but we probably should at least 
> alert the user that their DB (and, seemingly DB schema) is borked if 
> we notice that--whether we fail hard or "just try and see" or insert 
> some value in code when reading null from the DB column to try to 
> prevent errors.  My personal preference is to not spend a lot of time 
> coding to handle invalid data, but to log a message that makes it 
> possible for the user to figure out what's wrong and correct it.  That 
> said, I'm not at all against bulletproof (or bullet-resistant?) code.  
> (So, I guess that's completely useless advice, and maybe someone else 
> can be more helpful. :)

I don't know how the null values occurred. I did not see the user's 
database. I am using the services api so maybe it was an empty string. 
The xml parser will treat that as null.

I will get a fix for the Guide API to group by callsign and channel 
number as you suggested.

Peter

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