Getting active PostgreSQL connection's username as variable in QGIS?

Question

Is it possible to get login username from a current PostgreSQL layer connection in QGIS?

My goal is to automatically populate new objects in a layer with an editor login username (not @user_account_name or @user_full_name, because they are not related to a postgres connection).

Answer 1

I solved the problem by writing a custom expression function:

from qgis.core import *
from qgis.gui import *

@qgsfunction(args='auto', group='Custom')
def get_username(feature, parent, context):
    layer_name = context.variable('layer_name')
    layer = QgsProject.instance().mapLayersByName(layer_name)[0]
    username = QgsDataSourceUri(layer.dataProvider().dataSourceUri()).username()
    return username

now I can use a custom get_username() function in expression from