[mythtv-users] Mooting architecture for a DataDirect replacement

Steve Hodge stevehodge at gmail.com
Sun Jun 24 09:27:45 UTC 2007


On 6/24/07, Peter Schachte <schachte at csse.unimelb.edu.au> wrote:
>
> The real question is what an "update" is.  If an update is a
> whole listing for a single program, then you're right.  Otherwise, if an
> update
> is allowed to change parts of a listing for a program and not mention the
> parts
> it leaves unchanged, or to replace two or more programs but leave others
> unchanged, then the problem I'm describing can happen.  Here's a
> scenerio:  the
> current listing for a program has title T, description D, start time S,
> end time E.
>
> Update 1:  changes title to T1 and description to D1, and end time to E1.
> update 2:  changes title to T2 and start time to S2.
>
> Applied correctly, you wind up with title T2, description D1, start time
> S2,
> end time E1.  If update 2 arrives first and you apply it, you have title
> T2,
> description D, start time S2, end time E.  If update 1 now arrives and you
> apply it, you get title T1, description D1, start time S2, end time E1,
> which
> is wrong.  If you ignore it, you get title T2, description D, start time
> S2,
> end time E, which is also wrong.  Either way you lose.
>

You could make it so that updates only ever affect either one piece of data
or all the data for a program. That way you're back to being able to apply
updates correctly without keeping history or undo data, but it still covers
most situations - I'd expect you'd usually either be replacing one program
with another or changing only one or two things about a program.

Steve
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