[Qgis-developer] 1:many relation enhancements

[Matthias Kuhn]

Hi Hugo,

On 22.10.2014 09:13, Hugo Mercier wrote:
> Le 22/10/2014 08:39, Matthias Kuhn a écrit :
>> Hi Régis
>>
>> On 10/21/2014 09:44 PM, HAUBOURG wrote:
>>> Hi Matthias,
>>> Agregate functions could be provided by virtual table feature (qep is
>>> coming I think), I suppose we should chose one common way for advanced
>>> relationnal capabilities.
>> I agree that one common way is preferable, but actually this QEP itself
>> is already duplicating functionality (of QgsExpression) and nobody was
>> able yet to confirm that it is possible to optimize queries for
>> execution on the database with sqlite virtual tables. Something that is
>> a must from my point of view. I think it is a good initiative, but for
>> the aforementioned reasons I am not yet completely convinced, that it's
>> the one and only way.
> Hi,
>
> Since I'm the author of the mentioned QEP
> (https://github.com/qgis/QGIS-Enhancement-Proposals/pull/5), I have to
> answer :)
>
> What functionalities of expressions do you think it duplicates ?

Almost all (IN, LIKE, ILIKE, *, +, / just to name a few)
:)

>
> I don't see anything that prevents virtual layer queries from being
> optimized server-side. It has to be taken into account during the
> implementation of virtual layers, of course, but it is hard to exhibit
> the precise way it will work now without having an almost complete
> implementation.
I was referring to this discussion here.

https://github.com/qgis/QGIS-Enhancement-Proposals/pull/5#issuecomment-58148788

Sorry I did not respond again, but I don't think a complete optimization
is possible without having deep access to virtual table functionality in
sqlite (or having to parse the same SQL on our end and replace parts of
it which basically comes close to writing our own engine again).
But let's discuss this on the QEP PR instead of inside this ml thread.

> Anyway, it will try to complete my proposal with some more concrete
> material about that when I find time.
I'll make sure I'll have a look at it when I find time after you found
time :)

Best
Matthias

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