Re: [Gnumed-devel] Re: [Gnumed-update] - add extension method result caching as suggested by Ian [...]

[Karsten Hilbert]

> >- I maintain a bad feeling due to cache eviction policy being murky at best
> Where's the murk?
> If you change something with set_*, the local cache of the matching 
> get_* is junked, the cache is never wrong for local changes.
Correct.

> What you seem to be asking for is distributed cache eviction: a set_* on 
> one machine causes a cache refresh on all machines logged in to the same 
> patient.
Exactly.

> However this is pointless unless the GUI is updated too, and
> this is were it gets hairy.
Yes.

> Of course this is doable: all business objects do
> LISTEN <class name>_<pk> on instantiation (via the backend listener)
> were this makes sense (so not for elements of the past history, as 
> no-one should be changing that)
> and NOTIFY <class name>_<pk> on save_payload() or set_*()
Correct.

> However then GUI code has to register callbacks to know this has 
> happened. If were going to have callbacks, GUI code might as well 
> register with the business layer class via class methods, so they can be 
> called via a display () method after instantiation, too.
That is precisely how it is implemented today. gmRegetMixin.py
provides one way of fairly conveniently gaining that
functionality.

Karsten
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