[Qgis-developer] WFS Provider Strategies

[Matthias Kuhn]

On 20/07/16 17:35, Even Rouault wrote:

> Hi,
>
>> I am a bit confused by the WFS option *"Only request features
>> overlapping the view extent"*.
>>
>> In general, that's what every provider does by default and is a safe
>> strategy to use. If this option is unchecked, QGIS will just start
>> downloading features randomly until it hits a server limit (or not).
> Time to upgrade the servers to support WFS 2.0 paging :-)
Who could object to that :-)
>
>> The only reason why one would possibly want to do that is to warm a
>> cache on a layer where he know he will be getting all the features (in a
>> reasonable time). In this case, the option should probably be renamed
>> (to something containing the word "cache").
> The provider always cache (meaning keep in a temporary database the features 
> retrieved), whatever you check or uncheck this option. For example with the 
> default behaviour, zoom in in some region and wait for some or all features to 
> be retrieved, and zoom out. The provider will use the already downloaded 
> features first and then return the features coming from the background 
> downloading of the new request (using gml:id/fid to make sure not to return 
> already cached features).
In which case does that help? Isn't every cached feature downloaded
again (with potentially more up to date information) anyway?
>
>> Question: *is **there anybody using WFS with this option unchecked?* And
>> if yes, for what reason?
> Yes it is needed for some use cases. There are servers that have buggy 
> behaviour with BBOX requests combined with other filters. Or the cost of 
> solving a spatial request might be super high, making it more practical to 
> issue a GetFeature without a BBOX.
Ok, so it should be a super well hidden checkbox with a big warning sign
next to it?

Matthias