How to filter features in QGIS using the graphical processing modeler

This article describes a new algorithm for the processing modeler called feature filter algorithm. If you are already familiar with ETL concepts and the graphical modeler, you can directly jump to the section the feature filter algorithm. Building workflows for repetitive tasks When building workflows for simple or complex geodata infrastructures, one of the most […]

Best practices for writing Python QGIS Expression Functions

Recently there have been some questions and discussions about python based expression functions and how parameters like usesGeometry  need to be used. So I thought I’d quickly write down how this works. There is some intelligence If the geometry or a column is passed in as a parameter you do not need to request it manually, you […]

QGIS Expressions Engine: Performance boost

Expressions in QGIS are more and more widely used for all kinds of purposes. For example the recently introduced geometry generators allow drawing awesome effects with modified feature geometries on the fly. The last days at the QGIS developer meeting 2017, I spent some time looking into and improving the performance for expressions. This was […]