[Qgis-developer] QEP/RFC sqlite virtual tables

[Matthias Kuhn]

Hi Vincent

On 29.10.2014 10:51, Vincent Picavet wrote:
> Hello,
>
> Le mercredi 29 octobre 2014 08:34:11, Matthias Kuhn a écrit :
> [...]
>>> limitations. Only power users knowing what is really happening underneath
>>> will know what function to use, which is bad in UX terms.
>>> A comparison is OGR CSV driver versus CSV plugin... User has to know that
>>> both tools are differents, behaves differently with a different
>>> providers. Nothing in the GUI let you know that except try-fail
>>> approach.
>> The problem is that we have one proposal which can be available soon
>> with lots of functionality and a not-too-hard implementation. But we/I
>> lack knowledge if it performs well in every scenario and if it offers
>> the possibility to optimize.
> The thing is, we cannot forecast everything, and without a working prototype, 
> we will probably never be able to determine the behaviour for every scenario, 
> as we probably cannot imagine every scenario at all.
>
> "Premature optimization is the root of all evil."

It's not premature optimization. It's evaluation of a likely scenario
(at least nobody disagreed with a likely performance problem so far) and
early prevention of a vendor lock-in by looking ahead.

>
> At some point we need some working code to be able to start iterating over 
> something real, more than trying to imagine a perfect plan and see nothing 
> coming at the end.
>
> QEP are there to make sure the global orientation and design is good and is 
> coherent with the rest of the project. They cannot be fully exhaustive, and 
> there will probably be other QEP regarding this feature set to enhance and fix 
> the first implementation. 
> We could even go back if this approach proves to fail. Failure is progress 
> too.

There would also be the possibility to create this feature as a plugin
instead of implementing it in core. I think this has been discussed
before if I remember right. If it's in core it's very unlikely that we
will go back. And going back would certainly not make life easier for
power users.
I don't want to promote the option of implementing it as a plugin, I am
just listing it for the sake of completeness.

I think the most simple answer to my questions would probably be a
statement from the sqlite virtual table developers stating that they are
open to collaboration. That would literally vaporize any concerns I had.
It should not be hard to ask.

But again: I do like the general idea and I see the potential of this!
Please do not treat this message as a fundal disagreement with the QEP.

Matthias

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