uri = "dbname='test' host=localhost port=5432 user='user' password='password' key=gid type=POINT table="public"."test" (geom) sql="
    crs_id = 4326
    crs = QgsCoordinateReferenceSystem(crs_id,  QgsCoordinateReferenceSystem.EpsgCrsId)
    # layer - QGIS vector layer
    error = QgsVectorLayerImport.importLayer(layer, uri, "postgres", crs, False, False)
    if error[0] != 0:
        iface.messageBar().pushMessage(u'Error', error[1], QgsMessageBar.CRITICAL, 5)

from PyQt4.QtSql import *
    layer = iface.activeLayer()
    uri = QgsDataSourceURI()
    uri.setConnection("localhost", "5432", "your database", "user name", "password")
    uri.setDataSource("public", "table name", "geom")
    db = QSqlDatabase.addDatabase("QPSQL");
    db.setDatabaseName(uri.database())
    db.setPort(int(uri.port()))
    db.setUserName(uri.username())
    db.setPassword(uri.password())
    db.open()
    ok = db.open()
    ## below just shows that a table can be created and values can be inserted.
    query = db.exec_("""create table aaa (d INT4) """)
    query = db.exec_("""INSERT INTO aaa(d) VALUES(2) """)

layer = iface.activeLayer()
    for f in layer.getFeatures():
        dGeom = f.geometry()