[Qgis-user] BBox Filter for WFS

Thu Mar 26 13:28:44 PDT 2015

Thanks Giovanni-    It seems to me that the "cache features" option and the option to fetch only the features intersecting the current map extent should be 2 separate options. 

For example, when I open a WFS layer, I might want to retrieve only the features intersecting the current map extent. Once it is loaded, I would want QGIS to cache the features.

This is a common rendering technique used for WMS. A client requests an initial BBOX and renders the image. The when the client pans, a new request is made but only for the "missing" area. The original response is cached and merged with the second response. Just a thought...

Peter

     From: G. Allegri <giohappy at gmail.com>
 To: Peter Borissow <peter.borissow at yahoo.com> 
Cc: "qgis-user at lists.osgeo.org" <qgis-user at lists.osgeo.org> 
 Sent: Thursday, March 26, 2015 1:27 PM
 Subject: Re: [Qgis-user] BBox Filter for WFS

As Marco explained in the realted post on qgis-dev the bbox filter should be used if "cahce features" option is turned off, but at the moment it seems broken, maybe because of new improvements in the rendering process. The issue has been already reported in http://hub.qgis.org/issues/11968
In the meanwhile a manual filter could be set within the WFS add layer dialog.
giovanni
2015-03-26 16:07 GMT+01:00 G. Allegri <giohappy at gmail.com>:

It's an intereseting question Peter. I've verified that the wfs provider still requests the whole data the first time, then it stores eveything (and create a spatial index for subsequent calls).I suppose that sponsoring this feature could be the right way to have it, but I'm curious to know what the latest answer from Marco was referring to (I mean within the svn code he indicates) [1]
Giovanni
[1] http://hub.qgis.org/issues/1421#note-4
2015-03-25 12:25 GMT+01:00 Peter Borissow <peter.borissow at yahoo.com>:

Sorry for being impatient but I was wondering if anyone can shed some light on this issue.
I have a WFS that's serving out over a billion features (several million records per layer). When I add a layer from the WFS into QGIS, it calls DescribeFeature and then GetFeature without a BBOX filter. QGIS then waits for ALL of the data to come back (which can take a while). 
In the past, there was an option only fetch features that intersect the current map extent. Without this option, it is extremely difficult to do anything with the WFS using QGIS. 

IMHO, this is a pretty significant bug but hopefully one that should be really easy to fix. Afterall, the code was there at some point...

Related (unanswered) questions on stack exchange:

http://gis.stackexchange.com/questions/53387/quantumgis-1-8-how-to-define-bounding-box-within-add-wfs-layer-dialog
http://gis.stackexchange.com/questions/59656/is-there-free-desktop-wfs-client-with-bbox-support

Thanks,Peter

      From: Peter Borissow <peter.borissow at yahoo.com>
 To: "qgis-user at lists.osgeo.org" <qgis-user at lists.osgeo.org> 
 Sent: Monday, March 23, 2015 2:03 PM
 Subject: BBox Filter for WFS

Hello-    I noticed that the WFS client in QGIS 2.8 and 2.6 do not seem to pass a bbox filter when requesting features. 

It seems that in the past, QGIS had an option to only fetch features that intersect the current map extent:

http://hub.qgis.org/issues/1421

Based on this thread, it looks like this feature was disabled in 1.8:
http://osdir.com/ml/qgis-user-gis/2011-10/msg00308.html

Is this feature still missing or is there a way to enable this feature in the latest release?

Thanks,Peter

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-- 
Giovanni Allegri
http://about.me/giovanniallegriGis3W - http://gis3w.itIkare - http://ikare.it
Twitter: https://twitter.com/_giohappy_blog: http://blog.spaziogis.it
GEO+ geomatica in Italia http://bit.ly/GEOplus

-- 
Giovanni Allegri
http://about.me/giovanniallegriGis3W - http://gis3w.itIkare - http://ikare.it
Twitter: https://twitter.com/_giohappy_blog: http://blog.spaziogis.it
GEO+ geomatica in Italia http://bit.ly/GEOplus

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