[vtk-developers] Re: vtkSQLDatabase

[David C Thompson]

On Wed, 2007-11-28 at 15:26 -0500, Sebastien BARRE wrote:
> At 11/28/2007 03:12 PM, David C Thompson wrote:
> 
> >I think that falls under syntactic sugar. It would save having to call
> >Delete() and then CreateFromURL() when changing databases, but not
> >provide any change in performance (or perhaps a small decrease as each
> >call on the database would have to be forwarded to a concrete instance
> >if I understand your proposal correctly -- but I don't think it would be
> >a significant impact).
> >
> >In any event, you've sold me on SetURL being protected. Unless Sebastien
> >is morally opposed to CreateFromURL (it didn't sound like it to me),
> 
> I'm not, I was just passing by, curious about this new DB framework. 
> And I'm French, we don't have morales :)
Funny, I work with another French guy who keeps telling me it's us
Americans that are lacking. :-)

> More seriously, there was also a performance issue in the back of my 
> head, but I'm not sure if it is relevant right now: what about 
> caching?
I haven't seen any generic client-side database caching tools (but
plenty on the server side where databases are meant to perform more
queries than inserts). All the client-side caching I've seen is
application-specific. If you have pointers to generic client-side stuff,
I'd be interested in a pointer or two.

> Database caching can be a serious concern and lead to 
> significant improvements. While there are *already* DB caching tools 
> available that can be plugged at different levels, is it far fetched 
> to think that we could need one that uses information only available 
> at the VTK/pipeline level?
Well, I seem to recall MySQL's server-side DB caches just doing string
matches on queries. That's feasible on the client-side as well.

> If that's the case, wouldn't recreating an 
> object invalidate such a cache, if it was to be implemented at the 
> database class level?
You would have to invalidate the cache anyway if connecting to a
different database, right?

	David