The PostGIS Topology Editor plugin
Maintaining topology in the vector layers is very important; this results in greater data integrity and leads to more accurate analysis results. This recipe shows you how to edit PostGIS topology layers (in other words, layers with topology objects, such as edges, faces, and nodes) with QGIS.
Installation of PostGIS with topology support won't be covered in detail here because instructions for the different operating systems can be found on the project website at http://postgis.net/docs/manual-2.1/postgis_installation.html. If you are using Windows, PostGIS can be installed directly from the Stack Builder application, which is provided by the standard PostgreSQL installation, as described at http://www.bostongis.com/PrinterFriendly.aspx?content_name=postgis_tut01 ...