[Qgis-developer] Transaction in WFS Plugin

[Marco Hugentobler]

Hi Sunil

The code for WFS editing (and also for reading) is in the WFS provider, 
the plugin is only for the GUI.
Edits are sent in the 4 requests because those are the basic edit 
operations of the QGIS vector provider interface. So each data provider 
class implements addFeatures(), deleteFeatures(), etc. if it supports 
that operation. QGIS itself does not have a mechanism to support 
transaction over multiple edit operations.

Ideally, there would be methods like startTransaction(), 
commitTransaction(), discardTransaction() in the provider interface. 
Such methods would allow the WFS provider to send everything in a single 
transaction (and the methods could be ignored by other datasources 
without transaction support).

Maybe it would also be useful to send edits in a single transaction for 
PostGIS edits?

 >Please have a look to git - work was done recently by Marco 
Hugentobler and Bill Williamson.

This was about improving support for WFS filters and for incremental 
reading of features (not about editing).


Regards,
Marco

On 21.02.2012 04:08, Sunil Padda wrote:
> Hi,
>
> We are exposing some spatial data using GeoServer WFS. This data is 
> being rendered and edited using QGIS. We ran a small packet-capture 
> test to see how are transactions handled. The observations were as below:
>
>   * 4 separate requests were sent to WFS server
>   * The 4 requests have no common handle/identifier to signal they are
>     part of the same transaction
>   * The requests are for:
>       o Update Attributes for all features where attributes were changed
>       o Insert new features
>       o Update geometry for all features where geometry were changed
>       o Delete features
>   * WFS specification for Transaction operation supports combination
>     of Update, Insert and Delete as part of a single request
>
> Are our inferences correct? If so, can the WFS plugin be customized to 
> send all changes in a single Transaction request?
>
> Thanks,
> Sunil
>
>
>
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-- 
Dr. Marco Hugentobler
Sourcepole -  Linux&  Open Source Solutions
Churerstrasse 22, CH-8808 Pfäffikon SZ, Switzerland
marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
Technical Advisor QGIS Project Steering Committee

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