PyQGIS - load PostGIS layer as editable

Question

I can load a PostGIS layer on QGIS' map canvas but "Toggle Editing" button comes "inactive". How can I load vector layer as editable?

The code given below loads PostGIS layer on map canvas & "Toggle Editing" button comes "active" but once I run the script below in Python console; when I press "Toggle Editing" button, QGIS gives me an info message: "Start editing failed: Provider cannot be opened for editing":

sql = "(SELECT * FROM tablename)"
uri = QgsDataSourceURI()
uri.setConnection("localhost", "5432", "database", "postgres", "password")
uri.setDataSource("", sql, "geom", "", "gid")
vlayer = QgsVectorLayer(uri.uri(), "abc", "postgres")
QgsMapLayerRegistry.instance().addMapLayer(vlayer)

# should the layer be set as "active" ???

vlayer.dataProvider()
vlayer.dataProvider().capabilities()
vlayer.startEditing()
iface.actionToggleEditing().setEnabled(True)

Can someone please give me a hint on how to load an editable layer programmatically?

Answer 1

To load a shapefile into QGIS and set the layer as "editable", I executed the code below in the Python Concole:

LayerName =iface.addVectorLayer("/Path/To/Your/Shapefile.shp", "name", "ogr")
qgis.utils.iface.setActiveLayer(LayerName)
qgis.utils.iface.actionToggleEditing().trigger()

For PostGIS tables this blog post may help to set up the SELECT statement in order to load the PostGIS table successfully. Once the layer has been loaded into QGIS I assume the code below will enable/disable editing:

qgis.utils.iface.setActiveLayer(LayerName)
qgis.utils.iface.actionToggleEditing().trigger()

I have not tried the PostGIS example yet. This is my first post on GIS StackExchange so I hope it helps.

Answer 2

This post might help in your case. At least I had problems with PostGIS primary key missing and causing QGIS not to be able to edit the data stored in PostGIS.

Unable to edit PostGIS DB using QGIS 2.10, works on 2.8

Answer 3

You are incorrectly setting the data source. Also sql string is not needed. The below code should work for you.

sql=""
uri=QgsDataSourceURI()
uri.setConnection("host","port","dbname","user","password",QgsDataSourceURI.SSLdisable)
uri.setDataSource("schema","table_name","geometry_column","primary_key")
uri.setSrid("srid")
vlayer=QgsVectorLayer(uri.uri(),"abc","dbname")
QgsMapLayerRegistry.instance().addMapLayer(vlayer)