Duplicate entry in layer_styles table with PyQGIS

Question

I would like to duplicate an entry in QGIS (2.18.21) layer_styles table (in a PostGIS database) by the following steps:

From a PostGIS connection with styles saved to database add layer_styles table to the project and select it in the layers panel.

Using the following code on the python console I try to duplicate one of the features in the table:

>>> l = iface.activeLayer()
>>> f = [f for f in l.getFeatures()]
>>> f
[<qgis._core.QgsFeature object at 0x0000000029F4C378>, <qgis._core.QgsFeature object at 0x0000000029F4A048>]
>>> l.addFeature(f[0])
False

Now why does addFeature() return False here and how can I duplicate an entry in layer_styles table with PyQGIS?

Answer 1

if you want to take a style which is stored in the PostGIS Table layer_styles you don't apply it to the features but to the whole layer.

I Propose this solution which does not need a duplicated style:

layer = iface.activeLayer() # Holds table B
sql= "select  styleqml from public.layer_styles WHERE stylename = '%s'" %( "Your table name A")
query = QSqlQuery(self.db) # holds connection to your db
query.exec_(sql)
while query.next():
    style  = query.record().value("styleqml")
layer.applyNamedStyle(style)

With this approach, you get the style from layer A to layer B