[Qgis-developer] Virtual layers for QGIS

[Hugo Mercier]

Hi all,

Probably not the perfect timing, but anyway, I would like to move
forward on that topic of virtual layers.

The current implementation has already some use cases. It is not as
integrated into the expression engine as we might want, but it offers
possibilities that were hard to achieve before.

It consists merely of a new vector data provider. It does not depend on
particular modifications in QGIS. So the impact on the current API is
null. There will be some glue code in the app part of course,
but apart from that, I think including it into the core as just another
data provider won't bother other possible future implementations around
this concept. And it will serve as a functional prototype.

We may want to tag it as experimental or something like this, saying
that this is probably not the final (or the only) way QGIS will handle
the concept of "virtual layers" in the future.

And because it is only a data provider (... and a class in DBManager),
people may choose not to ship it with their binary version of QGIS if
they don't want to.

So ... is there any objection against that being pushed as a new vector
data provider for the 2.12 ?

On 11/05/2015 16:11, Hugo Mercier wrote:
> Hi all,
> 
> I've been recently involved in the development of "virtual layers" for
> QGIS. The topic has already been discussed previously. In a few words it
> allows to craft SQL queries (with spatial support) on any vector
> layer(s) that QGIS is able to load.
> 
> Now I have a plugin that is usuable and allows you to get familiar with
> the concept and test it.
> 
> More details are given here (with links to some videos):
> https://github.com/mhugo/qgis_vlayers
> 
> A binary version of the plugins for Windows 32bits is available here :
> http://91.121.102.10/vlayers/qgis_28_vlayers_4_win32.zip
> 
> An integration of virtual layers in db manager is provided, but it is
> better served with an improved version of db manager. A pull request
> about this is being reviewed (https://github.com/qgis/QGIS/pull/2025).
> You can also directly find it here :
> http://91.121.102.10/vlayers/db_manager_with_query_builder_and_vlayers.zip
> 
> Please do not hesitate to test this new functionality and report bugs or
> requests (here or on the github page)
> 
> Now the next step would be to lead toward a proper integration into QGIS
> core. I am already aware of some limitations that I have listed. I would
> be happy to have any other feedback.
> 
> The hackfest next week could also be a good place to discuss it (I will
> be presenting it during the conference)
> 
> Cheers.
> Hugo
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